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-. /////////////////////////////////////////////////////////////////////////////
-. This is the primary source of the Exim Manual. It is an xfpt document that is
-. converted into DocBook XML for subsequent conversion into printable and online
-. formats. The markup used herein is "standard" xfpt markup, with some extras.
-. The markup is summarized in a file called Markup.txt.
-.
-. WARNING: When you use the .new macro, make sure it appears *before* any
-. adjacent index items; otherwise you get an empty "paragraph" which causes
-. unwanted vertical space.
-. /////////////////////////////////////////////////////////////////////////////
-
-.include stdflags
-.include stdmacs
-
-. /////////////////////////////////////////////////////////////////////////////
-. This outputs the standard DocBook boilerplate.
-. /////////////////////////////////////////////////////////////////////////////
-
-.docbook
-
-. /////////////////////////////////////////////////////////////////////////////
-. These lines are processing instructions for the Simple DocBook Processor that
-. Philip Hazel has developed as a less cumbersome way of making PostScript and
-. PDFs than using xmlto and fop. They will be ignored by all other XML
-. processors.
-. /////////////////////////////////////////////////////////////////////////////
-
-.literal xml
-<?sdop
-  foot_right_recto="&chaptertitle; (&chapternumber;)"
-  foot_right_verso="&chaptertitle; (&chapternumber;)"
-  toc_chapter_blanks="yes,yes"
-  table_warn_overflow="overprint"
-?>
-.literal off
-
-. /////////////////////////////////////////////////////////////////////////////
-. This generates the outermost <book> element that wraps the entire document.
-. /////////////////////////////////////////////////////////////////////////////
-
-.book
-
-. /////////////////////////////////////////////////////////////////////////////
-. These definitions set some parameters and save some typing.
-. Update the Copyright year (only) when changing content.
-. /////////////////////////////////////////////////////////////////////////////
-
-.set previousversion "4.93"
-.include ./local_params
-
-.set ACL "access control lists (ACLs)"
-.set I   "&nbsp;&nbsp;&nbsp;&nbsp;"
-
-.macro copyyear
-2019
-.endmacro
-
-. /////////////////////////////////////////////////////////////////////////////
-. Additional xfpt markup used by this document, over and above the default
-. provided in the xfpt library.
-. /////////////////////////////////////////////////////////////////////////////
-
-. --- Override the &$ flag to automatically insert a $ with the variable name.
-
-.flag &$  $&   "<varname>$"  "</varname>"
-
-. --- Short flags for daggers in option headings. They will always be inside
-. --- an italic string, but we want the daggers to be in Roman.
-
-.flag &!!      "</emphasis>&dagger;<emphasis>"
-.flag &!?      "</emphasis>&Dagger;<emphasis>"
-
-. --- A macro for an Exim option definition heading, generating a one-line
-. --- table with four columns. For cases when the option name is given with
-. --- a space, so that it can be split, a fifth argument is used for the
-. --- index entry.
-
-.macro option
-.arg 5
-.oindex "&%$5%&"
-.endarg
-.arg -5
-.oindex "&%$1%&"
-.endarg
-.itable all 0 0 4 8* left 6* center 6* center 6* right
-.row "&%$1%&" "Use: &'$2'&" "Type: &'$3'&" "Default: &'$4'&"
-.endtable
-.endmacro
-
-. --- A macro for the common 2-column tables. The width of the first column
-. --- is suitable for the many tables at the start of the main options chapter;
-. --- a small number of other 2-column tables override it.
-
-.macro table2 196pt 254pt
-.itable none 0 0 2 $1 left $2 left
-.endmacro
-
-. --- A macro that generates .row, but puts &I; at the start of the first
-. --- argument, thus indenting it. Assume a minimum of two arguments, and
-. --- allow up to four arguments, which is as many as we'll ever need.
-
-.macro irow
-.arg 4
-.row "&I;$1" "$2" "$3" "$4"
-.endarg
-.arg -4
-.arg 3
-.row "&I;$1" "$2" "$3"
-.endarg
-.arg -3
-.row "&I;$1" "$2"
-.endarg
-.endarg
-.endmacro
-
-. --- Macros for option, variable, and concept index entries. For a "range"
-. --- style of entry, use .scindex for the start and .ecindex for the end. The
-. --- first argument of .scindex and the only argument of .ecindex must be the
-. --- ID that ties them together.
-
-.macro cindex
-&<indexterm role="concept">&
-&<primary>&$1&</primary>&
-.arg 2
-&<secondary>&$2&</secondary>&
-.endarg
-&</indexterm>&
-.endmacro
-
-.macro scindex
-&<indexterm role="concept" id="$1" class="startofrange">&
-&<primary>&$2&</primary>&
-.arg 3
-&<secondary>&$3&</secondary>&
-.endarg
-&</indexterm>&
-.endmacro
-
-.macro ecindex
-&<indexterm role="concept" startref="$1" class="endofrange"/>&
-.endmacro
-
-.macro oindex
-&<indexterm role="option">&
-&<primary>&$1&</primary>&
-.arg 2
-&<secondary>&$2&</secondary>&
-.endarg
-&</indexterm>&
-.endmacro
-
-.macro vindex
-&<indexterm role="variable">&
-&<primary>&$1&</primary>&
-.arg 2
-&<secondary>&$2&</secondary>&
-.endarg
-&</indexterm>&
-.endmacro
-
-.macro index
-.echo "** Don't use .index; use .cindex or .oindex or .vindex"
-.endmacro
-. ////////////////////////////////////////////////////////////////////////////
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. The <bookinfo> element is removed from the XML before processing for ASCII
-. output formats.
-. ////////////////////////////////////////////////////////////////////////////
-
-.literal xml
-<bookinfo>
-<title>Specification of the Exim Mail Transfer Agent</title>
-<titleabbrev>The Exim MTA</titleabbrev>
-<date>
-.fulldate
-</date>
-<author><firstname>Exim</firstname><surname>Maintainers</surname></author>
-<authorinitials>EM</authorinitials>
-<revhistory><revision>
-.versiondatexml
-  <authorinitials>EM</authorinitials>
-</revision></revhistory>
-<copyright><year>
-.copyyear
-           </year><holder>University of Cambridge</holder></copyright>
-</bookinfo>
-.literal off
-
-
-. /////////////////////////////////////////////////////////////////////////////
-. This chunk of literal XML implements index entries of the form "x, see y" and
-. "x, see also y". However, the DocBook DTD doesn't allow <indexterm> entries
-. at the top level, so we have to put the .chapter directive first.
-. /////////////////////////////////////////////////////////////////////////////
-
-.chapter "Introduction" "CHID1"
-.literal xml
-
-<indexterm role="variable">
-  <primary>$1, $2, etc.</primary>
-  <see><emphasis>numerical variables</emphasis></see>
-</indexterm>
-<indexterm role="concept">
-  <primary>address</primary>
-  <secondary>rewriting</secondary>
-  <see><emphasis>rewriting</emphasis></see>
-</indexterm>
-<indexterm role="concept">
-  <primary>Bounce Address Tag Validation</primary>
-  <see><emphasis>BATV</emphasis></see>
-</indexterm>
-<indexterm role="concept">
-  <primary>Client SMTP Authorization</primary>
-  <see><emphasis>CSA</emphasis></see>
-</indexterm>
-<indexterm role="concept">
-  <primary>CR character</primary>
-  <see><emphasis>carriage return</emphasis></see>
-</indexterm>
-<indexterm role="concept">
-  <primary>CRL</primary>
-  <see><emphasis>certificate revocation list</emphasis></see>
-</indexterm>
-<indexterm role="concept">
-  <primary>delivery</primary>
-  <secondary>failure report</secondary>
-  <see><emphasis>bounce message</emphasis></see>
-</indexterm>
-<indexterm role="concept">
-  <primary>dialup</primary>
-  <see><emphasis>intermittently connected hosts</emphasis></see>
-</indexterm>
-<indexterm role="concept">
-  <primary>exiscan</primary>
-  <see><emphasis>content scanning</emphasis></see>
-</indexterm>
-<indexterm role="concept">
-  <primary>failover</primary>
-  <see><emphasis>fallback</emphasis></see>
-</indexterm>
-<indexterm role="concept">
-  <primary>fallover</primary>
-  <see><emphasis>fallback</emphasis></see>
-</indexterm>
-<indexterm role="concept">
-  <primary>filter</primary>
-  <secondary>Sieve</secondary>
-  <see><emphasis>Sieve filter</emphasis></see>
-</indexterm>
-<indexterm role="concept">
-  <primary>ident</primary>
-  <see><emphasis>RFC 1413</emphasis></see>
-</indexterm>
-<indexterm role="concept">
-  <primary>LF character</primary>
-  <see><emphasis>linefeed</emphasis></see>
-</indexterm>
-<indexterm role="concept">
-  <primary>maximum</primary>
-  <seealso><emphasis>limit</emphasis></seealso>
-</indexterm>
-<indexterm role="concept">
-  <primary>monitor</primary>
-  <see><emphasis>Exim monitor</emphasis></see>
-</indexterm>
-<indexterm role="concept">
-  <primary>no_<emphasis>xxx</emphasis></primary>
-  <see>entry for xxx</see>
-</indexterm>
-<indexterm role="concept">
-  <primary>NUL</primary>
-  <see><emphasis>binary zero</emphasis></see>
-</indexterm>
-<indexterm role="concept">
-  <primary>passwd file</primary>
-  <see><emphasis>/etc/passwd</emphasis></see>
-</indexterm>
-<indexterm role="concept">
-  <primary>process id</primary>
-  <see><emphasis>pid</emphasis></see>
-</indexterm>
-<indexterm role="concept">
-  <primary>RBL</primary>
-  <see><emphasis>DNS list</emphasis></see>
-</indexterm>
-<indexterm role="concept">
-  <primary>redirection</primary>
-  <see><emphasis>address redirection</emphasis></see>
-</indexterm>
-<indexterm role="concept">
-  <primary>return path</primary>
-  <seealso><emphasis>envelope sender</emphasis></seealso>
-</indexterm>
-<indexterm role="concept">
-  <primary>scanning</primary>
-  <see><emphasis>content scanning</emphasis></see>
-</indexterm>
-<indexterm role="concept">
-  <primary>SSL</primary>
-  <see><emphasis>TLS</emphasis></see>
-</indexterm>
-<indexterm role="concept">
-  <primary>string</primary>
-  <secondary>expansion</secondary>
-  <see><emphasis>expansion</emphasis></see>
-</indexterm>
-<indexterm role="concept">
-  <primary>top bit</primary>
-  <see><emphasis>8-bit characters</emphasis></see>
-</indexterm>
-<indexterm role="concept">
-  <primary>variables</primary>
-  <see><emphasis>expansion, variables</emphasis></see>
-</indexterm>
-<indexterm role="concept">
-  <primary>zero, binary</primary>
-  <see><emphasis>binary zero</emphasis></see>
-</indexterm>
-
-.literal off
-
-
-. /////////////////////////////////////////////////////////////////////////////
-. This is the real start of the first chapter. See the comment above as to why
-. we can't have the .chapter line here.
-. chapter "Introduction"
-. /////////////////////////////////////////////////////////////////////////////
-
-Exim is a mail transfer agent (MTA) for hosts that are running Unix or
-Unix-like operating systems. It was designed on the assumption that it would be
-run on hosts that are permanently connected to the Internet. However, it can be
-used on intermittently connected hosts with suitable configuration adjustments.
-
-Configuration files currently exist for the following operating systems: AIX,
-BSD/OS (aka BSDI), Darwin (Mac OS X), DGUX, Dragonfly, FreeBSD, GNU/Hurd,
-GNU/Linux, HI-OSF (Hitachi), HI-UX, HP-UX, IRIX, MIPS RISCOS, NetBSD, OpenBSD,
-OpenUNIX, QNX, SCO, SCO SVR4.2 (aka UNIX-SV), Solaris (aka SunOS5), SunOS4,
-Tru64-Unix (formerly Digital UNIX, formerly DEC-OSF1), Ultrix, and UnixWare.
-Some of these operating systems are no longer current and cannot easily be
-tested, so the configuration files may no longer work in practice.
-
-There are also configuration files for compiling Exim in the Cygwin environment
-that can be installed on systems running Windows. However, this document does
-not contain any information about running Exim in the Cygwin environment.
-
-The terms and conditions for the use and distribution of Exim are contained in
-the file &_NOTICE_&. Exim is distributed under the terms of the GNU General
-Public Licence, a copy of which may be found in the file &_LICENCE_&.
-
-The use, supply, or promotion of Exim for the purpose of sending bulk,
-unsolicited electronic mail is incompatible with the basic aims of Exim,
-which revolve around the free provision of a service that enhances the quality
-of personal communications. The author of Exim regards indiscriminate
-mass-mailing as an antisocial, irresponsible abuse of the Internet.
-
-Exim owes a great deal to Smail 3 and its author, Ron Karr. Without the
-experience of running and working on the Smail 3 code, I could never have
-contemplated starting to write a new MTA. Many of the ideas and user interfaces
-were originally taken from Smail 3, though the actual code of Exim is entirely
-new, and has developed far beyond the initial concept.
-
-Many people, both in Cambridge and around the world, have contributed to the
-development and the testing of Exim, and to porting it to various operating
-systems. I am grateful to them all. The distribution now contains a file called
-&_ACKNOWLEDGMENTS_&, in which I have started recording the names of
-contributors.
-
-
-.section "Exim documentation" "SECID1"
-. Keep this example change bar when updating the documentation!
-
-.new
-.cindex "documentation"
-This edition of the Exim specification applies to version &version() of Exim.
-Substantive changes from the &previousversion; edition are marked in some
-renditions of this document; this paragraph is so marked if the rendition is
-capable of showing a change indicator.
-.wen
-
-This document is very much a reference manual; it is not a tutorial. The reader
-is expected to have some familiarity with the SMTP mail transfer protocol and
-with general Unix system administration. Although there are some discussions
-and examples in places, the information is mostly organized in a way that makes
-it easy to look up, rather than in a natural order for sequential reading.
-Furthermore, this manual aims to cover every aspect of Exim in detail, including
-a number of rarely-used, special-purpose features that are unlikely to be of
-very wide interest.
-
-.cindex "books about Exim"
-An &"easier"& discussion of Exim which provides more in-depth explanatory,
-introductory, and tutorial material can be found in a book entitled &'The Exim
-SMTP Mail Server'& (second edition, 2007), published by UIT Cambridge
-(&url(https://www.uit.co.uk/exim-book/)).
-
-The book also contains a chapter that gives a general introduction to SMTP and
-Internet mail. Inevitably, however, the book is unlikely to be fully up-to-date
-with the latest release of Exim. (Note that the earlier book about Exim,
-published by O'Reilly, covers Exim 3, and many things have changed in Exim 4.)
-
-.cindex "Debian" "information sources"
-If you are using a Debian distribution of Exim, you will find information about
-Debian-specific features in the file
-&_/usr/share/doc/exim4-base/README.Debian_&.
-The command &(man update-exim.conf)& is another source of Debian-specific
-information.
-
-.cindex "&_doc/NewStuff_&"
-.cindex "&_doc/ChangeLog_&"
-.cindex "change log"
-As Exim develops, there may be features in newer versions that have not
-yet made it into this document, which is updated only when the most significant
-digit of the fractional part of the version number changes. Specifications of
-new features that are not yet in this manual are placed in the file
-&_doc/NewStuff_& in the Exim distribution.
-
-Some features may be classified as &"experimental"&. These may change
-incompatibly while they are developing, or even be withdrawn. For this reason,
-they are not documented in this manual. Information about experimental features
-can be found in the file &_doc/experimental.txt_&.
-
-All changes to Exim (whether new features, bug fixes, or other kinds of
-change) are noted briefly in the file called &_doc/ChangeLog_&.
-
-.cindex "&_doc/spec.txt_&"
-This specification itself is available as an ASCII file in &_doc/spec.txt_& so
-that it can easily be searched with a text editor. Other files in the &_doc_&
-directory are:
-
-.table2 100pt
-.row &_OptionLists.txt_&     "list of all options in alphabetical order"
-.row &_dbm.discuss.txt_&     "discussion about DBM libraries"
-.row &_exim.8_&              "a man page of Exim's command line options"
-.row &_experimental.txt_&    "documentation of experimental features"
-.row &_filter.txt_&          "specification of the filter language"
-.row &_Exim3.upgrade_&       "upgrade notes from release 2 to release 3"
-.row &_Exim4.upgrade_&       "upgrade notes from release 3 to release 4"
-.row &_openssl.txt_&         "installing a current OpenSSL release"
-.endtable
-
-The main specification and the specification of the filtering language are also
-available in other formats (HTML, PostScript, PDF, and Texinfo). Section
-&<<SECTavail>>& below tells you how to get hold of these.
-
-
-
-.section "FTP site and websites" "SECID2"
-.cindex "website"
-.cindex "FTP site"
-The primary site for Exim source distributions is the &%exim.org%& FTP site,
-available over HTTPS, HTTP and FTP.  These services, and the &%exim.org%&
-website, are hosted at the University of Cambridge.
-
-.cindex "wiki"
-.cindex "FAQ"
-As well as Exim distribution tar files, the Exim website contains a number of
-differently formatted versions of the documentation. A recent addition to the
-online information is the Exim wiki (&url(https://wiki.exim.org)),
-which contains what used to be a separate FAQ, as well as various other
-examples, tips, and know-how that have been contributed by Exim users.
-The wiki site should always redirect to the correct place, which is currently
-provided by GitHub, and is open to editing by anyone with a GitHub account.
-
-.cindex Bugzilla
-An Exim Bugzilla exists at &url(https://bugs.exim.org). You can use
-this to report bugs, and also to add items to the wish list. Please search
-first to check that you are not duplicating a previous entry.
-Please do not ask for configuration help in the bug-tracker.
-
-
-.section "Mailing lists" "SECID3"
-.cindex "mailing lists" "for Exim users"
-The following Exim mailing lists exist:
-
-.table2 140pt
-.row &'exim-announce@exim.org'&   "Moderated, low volume announcements list"
-.row &'exim-users@exim.org'&      "General discussion list"
-.row &'exim-dev@exim.org'&        "Discussion of bugs, enhancements, etc."
-.row &'exim-cvs@exim.org'&        "Automated commit messages from the VCS"
-.endtable
-
-You can subscribe to these lists, change your existing subscriptions, and view
-or search the archives via the mailing lists link on the Exim home page.
-.cindex "Debian" "mailing list for"
-If you are using a Debian distribution of Exim, you may wish to subscribe to
-the Debian-specific mailing list &'pkg-exim4-users@lists.alioth.debian.org'&
-via this web page:
-.display
-&url(https://alioth-lists.debian.net/cgi-bin/mailman/listinfo/pkg-exim4-users)
-.endd
-Please ask Debian-specific questions on that list and not on the general Exim
-lists.
-
-.section "Bug reports" "SECID5"
-.cindex "bug reports"
-.cindex "reporting bugs"
-Reports of obvious bugs can be emailed to &'bugs@exim.org'& or reported
-via the Bugzilla (&url(https://bugs.exim.org)). However, if you are unsure
-whether some behaviour is a bug or not, the best thing to do is to post a
-message to the &'exim-dev'& mailing list and have it discussed.
-
-
-
-.section "Where to find the Exim distribution" "SECTavail"
-.cindex "FTP site"
-.cindex "HTTPS download site"
-.cindex "distribution" "FTP site"
-.cindex "distribution" "https site"
-The master distribution site for the Exim distribution is
-.display
-&url(https://downloads.exim.org/)
-.endd
-The service is available over HTTPS, HTTP and FTP.
-We encourage people to migrate to HTTPS.
-
-The content served at &url(https://downloads.exim.org/) is identical to the
-content served at &url(https://ftp.exim.org/pub/exim) and
-&url(ftp://ftp.exim.org/pub/exim).
-
-If accessing via a hostname containing &'ftp'&, then the file references that
-follow are relative to the &_exim_& directories at these sites.
-If accessing via the hostname &'downloads'& then the subdirectories described
-here are top-level directories.
-
-There are now quite a number of independent mirror sites around
-the world. Those that I know about are listed in the file called &_Mirrors_&.
-
-Within the top exim directory there are subdirectories called &_exim3_& (for
-previous Exim 3 distributions), &_exim4_& (for the latest Exim 4
-distributions), and &_Testing_& for testing versions. In the &_exim4_&
-subdirectory, the current release can always be found in files called
-.display
-&_exim-n.nn.tar.xz_&
-&_exim-n.nn.tar.gz_&
-&_exim-n.nn.tar.bz2_&
-.endd
-where &'n.nn'& is the highest such version number in the directory. The three
-files contain identical data; the only difference is the type of compression.
-The &_.xz_& file is usually the smallest, while the &_.gz_& file is the
-most portable to old systems.
-
-.cindex "distribution" "signing details"
-.cindex "distribution" "public key"
-.cindex "public key for signed distribution"
-The distributions will be PGP signed by an individual key of the Release
-Coordinator.  This key will have a uid containing an email address in the
-&'exim.org'& domain and will have signatures from other people, including
-other Exim maintainers.  We expect that the key will be in the "strong set" of
-PGP keys.  There should be a trust path to that key from the Exim Maintainer's
-PGP keys, a version of which can be found in the release directory in the file
-&_Exim-Maintainers-Keyring.asc_&.  All keys used will be available in public keyserver pools,
-such as &'pool.sks-keyservers.net'&.
-
-At the time of the last update, releases were being made by Jeremy Harris and signed
-with key &'0xBCE58C8CE41F32DF'&.  Other recent keys used for signing are those
-of Heiko Schlittermann, &'0x26101B62F69376CE'&,
-and of Phil Pennock, &'0x4D1E900E14C1CC04'&.
-
-The signatures for the tar bundles are in:
-.display
-&_exim-n.nn.tar.xz.asc_&
-&_exim-n.nn.tar.gz.asc_&
-&_exim-n.nn.tar.bz2.asc_&
-.endd
-For each released version, the log of changes is made available in a
-separate file in the directory &_ChangeLogs_& so that it is possible to
-find out what has changed without having to download the entire distribution.
-
-.cindex "documentation" "available formats"
-The main distribution contains ASCII versions of this specification and other
-documentation; other formats of the documents are available in separate files
-inside the &_exim4_& directory of the FTP site:
-.display
-&_exim-html-n.nn.tar.gz_&
-&_exim-pdf-n.nn.tar.gz_&
-&_exim-postscript-n.nn.tar.gz_&
-&_exim-texinfo-n.nn.tar.gz_&
-.endd
-These tar files contain only the &_doc_& directory, not the complete
-distribution, and are also available in &_.bz2_& and &_.xz_& forms.
-
-
-.section "Limitations" "SECID6"
-.ilist
-.cindex "limitations of Exim"
-.cindex "bang paths" "not handled by Exim"
-Exim is designed for use as an Internet MTA, and therefore handles addresses in
-RFC 2822 domain format only. It cannot handle UUCP &"bang paths"&, though
-simple two-component bang paths can be converted by a straightforward rewriting
-configuration. This restriction does not prevent Exim from being interfaced to
-UUCP as a transport mechanism, provided that domain addresses are used.
-.next
-.cindex "domainless addresses"
-.cindex "address" "without domain"
-Exim insists that every address it handles has a domain attached. For incoming
-local messages, domainless addresses are automatically qualified with a
-configured domain value. Configuration options specify from which remote
-systems unqualified addresses are acceptable. These are then qualified on
-arrival.
-.next
-.cindex "transport" "external"
-.cindex "external transports"
-The only external transport mechanisms that are currently implemented are SMTP
-and LMTP over a TCP/IP network (including support for IPv6). However, a pipe
-transport is available, and there are facilities for writing messages to files
-and pipes, optionally in &'batched SMTP'& format; these facilities can be used
-to send messages to other transport mechanisms such as UUCP, provided they can
-handle domain-style addresses. Batched SMTP input is also catered for.
-.next
-Exim is not designed for storing mail for dial-in hosts. When the volumes of
-such mail are large, it is better to get the messages &"delivered"& into files
-(that is, off Exim's queue) and subsequently passed on to the dial-in hosts by
-other means.
-.next
-Although Exim does have basic facilities for scanning incoming messages, these
-are not comprehensive enough to do full virus or spam scanning. Such operations
-are best carried out using additional specialized software packages. If you
-compile Exim with the content-scanning extension, straightforward interfaces to
-a number of common scanners are provided.
-.endlist
-
-
-.section "Runtime configuration" "SECID7"
-Exim's runtime configuration is held in a single text file that is divided
-into a number of sections. The entries in this file consist of keywords and
-values, in the style of Smail 3 configuration files. A default configuration
-file which is suitable for simple online installations is provided in the
-distribution, and is described in chapter &<<CHAPdefconfil>>& below.
-
-
-.section "Calling interface" "SECID8"
-.cindex "Sendmail compatibility" "command line interface"
-Like many MTAs, Exim has adopted the Sendmail command line interface so that it
-can be a straight replacement for &_/usr/lib/sendmail_& or
-&_/usr/sbin/sendmail_& when sending mail, but you do not need to know anything
-about Sendmail in order to run Exim. For actions other than sending messages,
-Sendmail-compatible options also exist, but those that produce output (for
-example, &%-bp%&, which lists the messages in the queue) do so in Exim's own
-format. There are also some additional options that are compatible with Smail
-3, and some further options that are new to Exim. Chapter &<<CHAPcommandline>>&
-documents all Exim's command line options. This information is automatically
-made into the man page that forms part of the Exim distribution.
-
-Control of messages in the queue can be done via certain privileged command
-line options. There is also an optional monitor program called &'eximon'&,
-which displays current information in an X window, and which contains a menu
-interface to Exim's command line administration options.
-
-
-
-.section "Terminology" "SECID9"
-.cindex "terminology definitions"
-.cindex "body of message" "definition of"
-The &'body'& of a message is the actual data that the sender wants to transmit.
-It is the last part of a message and is separated from the &'header'& (see
-below) by a blank line.
-
-.cindex "bounce message" "definition of"
-When a message cannot be delivered, it is normally returned to the sender in a
-delivery failure message or a &"non-delivery report"& (NDR). The term
-&'bounce'& is commonly used for this action, and the error reports are often
-called &'bounce messages'&. This is a convenient shorthand for &"delivery
-failure error report"&. Such messages have an empty sender address in the
-message's &'envelope'& (see below) to ensure that they cannot themselves give
-rise to further bounce messages.
-
-The term &'default'& appears frequently in this manual. It is used to qualify a
-value which is used in the absence of any setting in the configuration. It may
-also qualify an action which is taken unless a configuration setting specifies
-otherwise.
-
-The term &'defer'& is used when the delivery of a message to a specific
-destination cannot immediately take place for some reason (a remote host may be
-down, or a user's local mailbox may be full). Such deliveries are &'deferred'&
-until a later time.
-
-The word &'domain'& is sometimes used to mean all but the first component of a
-host's name. It is &'not'& used in that sense here, where it normally refers to
-the part of an email address following the @ sign.
-
-.cindex "envelope, definition of"
-.cindex "sender" "definition of"
-A message in transit has an associated &'envelope'&, as well as a header and a
-body. The envelope contains a sender address (to which bounce messages should
-be delivered), and any number of recipient addresses. References to the
-sender or the recipients of a message usually mean the addresses in the
-envelope. An MTA uses these addresses for delivery, and for returning bounce
-messages, not the addresses that appear in the header lines.
-
-.cindex "message" "header, definition of"
-.cindex "header section" "definition of"
-The &'header'& of a message is the first part of a message's text, consisting
-of a number of lines, each of which has a name such as &'From:'&, &'To:'&,
-&'Subject:'&, etc. Long header lines can be split over several text lines by
-indenting the continuations. The header is separated from the body by a blank
-line.
-
-.cindex "local part" "definition of"
-.cindex "domain" "definition of"
-The term &'local part'&, which is taken from RFC 2822, is used to refer to the
-part of an email address that precedes the @ sign. The part that follows the
-@ sign is called the &'domain'& or &'mail domain'&.
-
-.cindex "local delivery" "definition of"
-.cindex "remote delivery, definition of"
-The terms &'local delivery'& and &'remote delivery'& are used to distinguish
-delivery to a file or a pipe on the local host from delivery by SMTP over
-TCP/IP to another host. As far as Exim is concerned, all hosts other than the
-host it is running on are &'remote'&.
-
-.cindex "return path" "definition of"
-&'Return path'& is another name that is used for the sender address in a
-message's envelope.
-
-.cindex "queue" "definition of"
-The term &'queue'& is used to refer to the set of messages awaiting delivery
-because this term is in widespread use in the context of MTAs. However, in
-Exim's case, the reality is more like a pool than a queue, because there is
-normally no ordering of waiting messages.
-
-.cindex "queue runner" "definition of"
-The term &'queue runner'& is used to describe a process that scans the queue
-and attempts to deliver those messages whose retry times have come. This term
-is used by other MTAs and also relates to the command &%runq%&, but in Exim
-the waiting messages are normally processed in an unpredictable order.
-
-.cindex "spool directory" "definition of"
-The term &'spool directory'& is used for a directory in which Exim keeps the
-messages in its queue &-- that is, those that it is in the process of
-delivering. This should not be confused with the directory in which local
-mailboxes are stored, which is called a &"spool directory"& by some people. In
-the Exim documentation, &"spool"& is always used in the first sense.
-
-
-
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "Incorporated code" "CHID2"
-.cindex "incorporated code"
-.cindex "regular expressions" "library"
-.cindex "PCRE"
-.cindex "OpenDMARC"
-A number of pieces of external code are included in the Exim distribution.
-
-.ilist
-Regular expressions are supported in the main Exim program and in the
-Exim monitor using the freely-distributable PCRE library, copyright
-&copy; University of Cambridge. The source to PCRE is no longer shipped with
-Exim, so you will need to use the version of PCRE shipped with your system,
-or obtain and install the full version of the library from
-&url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre).
-.next
-.cindex "cdb" "acknowledgment"
-Support for the cdb (Constant DataBase) lookup method is provided by code
-contributed by Nigel Metheringham of (at the time he contributed it) Planet
-Online Ltd. The implementation is completely contained within the code of Exim.
-It does not link against an external cdb library. The code contains the
-following statements:
-
-.blockquote
-Copyright &copy; 1998 Nigel Metheringham, Planet Online Ltd
-
-This program is free software; you can redistribute it and/or modify it under
-the terms of the GNU General Public License as published by the Free Software
-Foundation; either version 2 of the License, or (at your option) any later
-version.
-This code implements Dan Bernstein's Constant DataBase (cdb) spec. Information,
-the spec and sample code for cdb can be obtained from
-&url(https://cr.yp.to/cdb.html). This implementation borrows
-some code from Dan Bernstein's implementation (which has no license
-restrictions applied to it).
-.endblockquote
-.next
-.cindex "SPA authentication"
-.cindex "Samba project"
-.cindex "Microsoft Secure Password Authentication"
-Client support for Microsoft's &'Secure Password Authentication'& is provided
-by code contributed by Marc Prud'hommeaux. Server support was contributed by
-Tom Kistner. This includes code taken from the Samba project, which is released
-under the Gnu GPL.
-.next
-.cindex "Cyrus"
-.cindex "&'pwcheck'& daemon"
-.cindex "&'pwauthd'& daemon"
-Support for calling the Cyrus &'pwcheck'& and &'saslauthd'& daemons is provided
-by code taken from the Cyrus-SASL library and adapted by Alexander S.
-Sabourenkov. The permission notice appears below, in accordance with the
-conditions expressed therein.
-
-.blockquote
-Copyright &copy; 2001 Carnegie Mellon University.  All rights reserved.
-
-Redistribution and use in source and binary forms, with or without
-modification, are permitted provided that the following conditions
-are met:
-
-.olist
-Redistributions of source code must retain the above copyright
-notice, this list of conditions and the following disclaimer.
-.next
-Redistributions in binary form must reproduce the above copyright
-notice, this list of conditions and the following disclaimer in
-the documentation and/or other materials provided with the
-distribution.
-.next
-The name &"Carnegie Mellon University"& must not be used to
-endorse or promote products derived from this software without
-prior written permission. For permission or any other legal
-details, please contact
-.display
-              Office of Technology Transfer
-              Carnegie Mellon University
-              5000 Forbes Avenue
-              Pittsburgh, PA  15213-3890
-              (412) 268-4387, fax: (412) 268-7395
-              tech-transfer@andrew.cmu.edu
-.endd
-.next
-Redistributions of any form whatsoever must retain the following
-acknowledgment:
-
-&"This product includes software developed by Computing Services
-at Carnegie Mellon University (&url(https://www.cmu.edu/computing/)."&
-
-CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
-THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
-AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
-FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
-WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
-AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
-OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
-.endlist
-.endblockquote
-
-.next
-.cindex "Exim monitor" "acknowledgment"
-.cindex "X-windows"
-.cindex "Athena"
-The Exim Monitor program, which is an X-Window application, includes
-modified versions of the Athena StripChart and TextPop widgets.
-This code is copyright by DEC and MIT, and their permission notice appears
-below, in accordance with the conditions expressed therein.
-
-.blockquote
-Copyright 1987, 1988 by Digital Equipment Corporation, Maynard, Massachusetts,
-and the Massachusetts Institute of Technology, Cambridge, Massachusetts.
-
-All Rights Reserved
-
-Permission to use, copy, modify, and distribute this software and its
-documentation for any purpose and without fee is hereby granted,
-provided that the above copyright notice appear in all copies and that
-both that copyright notice and this permission notice appear in
-supporting documentation, and that the names of Digital or MIT not be
-used in advertising or publicity pertaining to distribution of the
-software without specific, written prior permission.
-
-DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
-ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
-DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
-ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
-WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
-ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
-SOFTWARE.
-.endblockquote
-
-.next
-.cindex "opendmarc" "acknowledgment"
-The DMARC implementation uses the OpenDMARC library which is Copyrighted by
-The Trusted Domain Project. Portions of Exim source which use OpenDMARC
-derived code are indicated in the respective source files. The full OpenDMARC
-license is provided in the LICENSE.opendmarc file contained in the distributed
-source code.
-
-.next
-Many people have contributed code fragments, some large, some small, that were
-not covered by any specific license requirements. It is assumed that the
-contributors are happy to see their code incorporated into Exim under the GPL.
-.endlist
-
-
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "How Exim receives and delivers mail" "CHID11" &&&
-         "Receiving and delivering mail"
-
-
-.section "Overall philosophy" "SECID10"
-.cindex "design philosophy"
-Exim is designed to work efficiently on systems that are permanently connected
-to the Internet and are handling a general mix of mail. In such circumstances,
-most messages can be delivered immediately. Consequently, Exim does not
-maintain independent queues of messages for specific domains or hosts, though
-it does try to send several messages in a single SMTP connection after a host
-has been down, and it also maintains per-host retry information.
-
-
-.section "Policy control" "SECID11"
-.cindex "policy control" "overview"
-Policy controls are now an important feature of MTAs that are connected to the
-Internet. Perhaps their most important job is to stop MTAs from being abused as
-&"open relays"& by misguided individuals who send out vast amounts of
-unsolicited junk and want to disguise its source. Exim provides flexible
-facilities for specifying policy controls on incoming mail:
-
-.ilist
-.cindex "&ACL;" "introduction"
-Exim 4 (unlike previous versions of Exim) implements policy controls on
-incoming mail by means of &'Access Control Lists'& (ACLs). Each list is a
-series of statements that may either grant or deny access. ACLs can be used at
-several places in the SMTP dialogue while receiving a message from a remote
-host. However, the most common places are after each RCPT command, and at the
-very end of the message. The sysadmin can specify conditions for accepting or
-rejecting individual recipients or the entire message, respectively, at these
-two points (see chapter &<<CHAPACL>>&). Denial of access results in an SMTP
-error code.
-.next
-An ACL is also available for locally generated, non-SMTP messages. In this
-case, the only available actions are to accept or deny the entire message.
-.next
-When Exim is compiled with the content-scanning extension, facilities are
-provided in the ACL mechanism for passing the message to external virus and/or
-spam scanning software. The result of such a scan is passed back to the ACL,
-which can then use it to decide what to do with the message.
-.next
-When a message has been received, either from a remote host or from the local
-host, but before the final acknowledgment has been sent, a locally supplied C
-function called &[local_scan()]& can be run to inspect the message and decide
-whether to accept it or not (see chapter &<<CHAPlocalscan>>&). If the message
-is accepted, the list of recipients can be modified by the function.
-.next
-Using the &[local_scan()]& mechanism is another way of calling external scanner
-software. The &%SA-Exim%& add-on package works this way. It does not require
-Exim to be compiled with the content-scanning extension.
-.next
-After a message has been accepted, a further checking mechanism is available in
-the form of the &'system filter'& (see chapter &<<CHAPsystemfilter>>&). This
-runs at the start of every delivery process.
-.endlist
-
-
-
-.section "User filters" "SECID12"
-.cindex "filter" "introduction"
-.cindex "Sieve filter"
-In a conventional Exim configuration, users are able to run private filters by
-setting up appropriate &_.forward_& files in their home directories. See
-chapter &<<CHAPredirect>>& (about the &(redirect)& router) for the
-configuration needed to support this, and the separate document entitled
-&'Exim's interfaces to mail filtering'& for user details. Two different kinds
-of filtering are available:
-
-.ilist
-Sieve filters are written in the standard filtering language that is defined
-by RFC 3028.
-.next
-Exim filters are written in a syntax that is unique to Exim, but which is more
-powerful than Sieve, which it pre-dates.
-.endlist
-
-User filters are run as part of the routing process, described below.
-
-
-
-.section "Message identification" "SECTmessiden"
-.cindex "message ids" "details of format"
-.cindex "format" "of message id"
-.cindex "id of message"
-.cindex "base62"
-.cindex "base36"
-.cindex "Darwin"
-.cindex "Cygwin"
-Every message handled by Exim is given a &'message id'& which is sixteen
-characters long. It is divided into three parts, separated by hyphens, for
-example &`16VDhn-0001bo-D3`&. Each part is a sequence of letters and digits,
-normally encoding numbers in base 62. However, in the Darwin operating
-system (Mac OS X) and when Exim is compiled to run under Cygwin, base 36
-(avoiding the use of lower case letters) is used instead, because the message
-id is used to construct filenames, and the names of files in those systems are
-not always case-sensitive.
-
-.cindex "pid (process id)" "re-use of"
-The detail of the contents of the message id have changed as Exim has evolved.
-Earlier versions relied on the operating system not re-using a process id (pid)
-within one second. On modern operating systems, this assumption can no longer
-be made, so the algorithm had to be changed. To retain backward compatibility,
-the format of the message id was retained, which is why the following rules are
-somewhat eccentric:
-
-.ilist
-The first six characters of the message id are the time at which the message
-started to be received, to a granularity of one second. That is, this field
-contains the number of seconds since the start of the epoch (the normal Unix
-way of representing the date and time of day).
-.next
-After the first hyphen, the next six characters are the id of the process that
-received the message.
-.next
-There are two different possibilities for the final two characters:
-.olist
-.oindex "&%localhost_number%&"
-If &%localhost_number%& is not set, this value is the fractional part of the
-time of reception, normally in units of 1/2000 of a second, but for systems
-that must use base 36 instead of base 62 (because of case-insensitive file
-systems), the units are 1/1000 of a second.
-.next
-If &%localhost_number%& is set, it is multiplied by 200 (100) and added to
-the fractional part of the time, which in this case is in units of 1/200
-(1/100) of a second.
-.endlist
-.endlist
-
-After a message has been received, Exim waits for the clock to tick at the
-appropriate resolution before proceeding, so that if another message is
-received by the same process, or by another process with the same (re-used)
-pid, it is guaranteed that the time will be different. In most cases, the clock
-will already have ticked while the message was being received.
-
-
-.section "Receiving mail" "SECID13"
-.cindex "receiving mail"
-.cindex "message" "reception"
-The only way Exim can receive mail from another host is using SMTP over
-TCP/IP, in which case the sender and recipient addresses are transferred using
-SMTP commands. However, from a locally running process (such as a user's MUA),
-there are several possibilities:
-
-.ilist
-If the process runs Exim with the &%-bm%& option, the message is read
-non-interactively (usually via a pipe), with the recipients taken from the
-command line, or from the body of the message if &%-t%& is also used.
-.next
-If the process runs Exim with the &%-bS%& option, the message is also read
-non-interactively, but in this case the recipients are listed at the start of
-the message in a series of SMTP RCPT commands, terminated by a DATA
-command. This is called &"batch SMTP"& format,
-but it isn't really SMTP. The SMTP commands are just another way of passing
-envelope addresses in a non-interactive submission.
-.next
-If the process runs Exim with the &%-bs%& option, the message is read
-interactively, using the SMTP protocol. A two-way pipe is normally used for
-passing data between the local process and the Exim process.
-This is &"real"& SMTP and is handled in the same way as SMTP over TCP/IP. For
-example, the ACLs for SMTP commands are used for this form of submission.
-.next
-A local process may also make a TCP/IP call to the host's loopback address
-(127.0.0.1) or any other of its IP addresses. When receiving messages, Exim
-does not treat the loopback address specially. It treats all such connections
-in the same way as connections from other hosts.
-.endlist
-
-
-.cindex "message sender, constructed by Exim"
-.cindex "sender" "constructed by Exim"
-In the three cases that do not involve TCP/IP, the sender address is
-constructed from the login name of the user that called Exim and a default
-qualification domain (which can be set by the &%qualify_domain%& configuration
-option). For local or batch SMTP, a sender address that is passed using the
-SMTP MAIL command is ignored. However, the system administrator may allow
-certain users (&"trusted users"&) to specify a different sender addresses
-unconditionally, or all users to specify certain forms of different sender
-address. The &%-f%& option or the SMTP MAIL command is used to specify these
-different addresses. See section &<<SECTtrustedadmin>>& for details of trusted
-users, and the &%untrusted_set_sender%& option for a way of allowing untrusted
-users to change sender addresses.
-
-Messages received by either of the non-interactive mechanisms are subject to
-checking by the non-SMTP ACL if one is defined. Messages received using SMTP
-(either over TCP/IP or interacting with a local process) can be checked by a
-number of ACLs that operate at different times during the SMTP session. Either
-individual recipients or the entire message can be rejected if local policy
-requirements are not met. The &[local_scan()]& function (see chapter
-&<<CHAPlocalscan>>&) is run for all incoming messages.
-
-Exim can be configured not to start a delivery process when a message is
-received; this can be unconditional, or depend on the number of incoming SMTP
-connections or the system load. In these situations, new messages wait on the
-queue until a queue runner process picks them up. However, in standard
-configurations under normal conditions, delivery is started as soon as a
-message is received.
-
-
-
-
-
-.section "Handling an incoming message" "SECID14"
-.cindex "spool directory" "files that hold a message"
-.cindex "file" "how a message is held"
-When Exim accepts a message, it writes two files in its spool directory. The
-first contains the envelope information, the current status of the message, and
-the header lines, and the second contains the body of the message. The names of
-the two spool files consist of the message id, followed by &`-H`& for the
-file containing the envelope and header, and &`-D`& for the data file.
-
-.cindex "spool directory" "&_input_& sub-directory"
-By default, all these message files are held in a single directory called
-&_input_& inside the general Exim spool directory. Some operating systems do
-not perform very well if the number of files in a directory gets large; to
-improve performance in such cases, the &%split_spool_directory%& option can be
-used. This causes Exim to split up the input files into 62 sub-directories
-whose names are single letters or digits. When this is done, the queue is
-processed one sub-directory at a time instead of all at once, which can improve
-overall performance even when there are not enough files in each directory to
-affect file system performance.
-
-The envelope information consists of the address of the message's sender and
-the addresses of the recipients. This information is entirely separate from
-any addresses contained in the header lines. The status of the message includes
-a list of recipients who have already received the message. The format of the
-first spool file is described in chapter &<<CHAPspool>>&.
-
-.cindex "rewriting" "addresses"
-Address rewriting that is specified in the rewrite section of the configuration
-(see chapter &<<CHAPrewrite>>&) is done once and for all on incoming addresses,
-both in the header lines and the envelope, at the time the message is accepted.
-If during the course of delivery additional addresses are generated (for
-example, via aliasing), these new addresses are rewritten as soon as they are
-generated. At the time a message is actually delivered (transported) further
-rewriting can take place; because this is a transport option, it can be
-different for different forms of delivery. It is also possible to specify the
-addition or removal of certain header lines at the time the message is
-delivered (see chapters &<<CHAProutergeneric>>& and
-&<<CHAPtransportgeneric>>&).
-
-
-
-.section "Life of a message" "SECID15"
-.cindex "message" "life of"
-.cindex "message" "frozen"
-A message remains in the spool directory until it is completely delivered to
-its recipients or to an error address, or until it is deleted by an
-administrator or by the user who originally created it. In cases when delivery
-cannot proceed &-- for example when a message can neither be delivered to its
-recipients nor returned to its sender, the message is marked &"frozen"& on the
-spool, and no more deliveries are attempted.
-
-.cindex "frozen messages" "thawing"
-.cindex "message" "thawing frozen"
-An administrator can &"thaw"& such messages when the problem has been
-corrected, and can also freeze individual messages by hand if necessary. In
-addition, an administrator can force a delivery error, causing a bounce message
-to be sent.
-
-.oindex "&%timeout_frozen_after%&"
-.oindex "&%ignore_bounce_errors_after%&"
-There are options called &%ignore_bounce_errors_after%& and
-&%timeout_frozen_after%&, which discard frozen messages after a certain time.
-The first applies only to frozen bounces, the second to all frozen messages.
-
-.cindex "message" "log file for"
-.cindex "log" "file for each message"
-While Exim is working on a message, it writes information about each delivery
-attempt to its main log file. This includes successful, unsuccessful, and
-delayed deliveries for each recipient (see chapter &<<CHAPlog>>&). The log
-lines are also written to a separate &'message log'& file for each message.
-These logs are solely for the benefit of the administrator and are normally
-deleted along with the spool files when processing of a message is complete.
-The use of individual message logs can be disabled by setting
-&%no_message_logs%&; this might give an improvement in performance on very busy
-systems.
-
-.cindex "journal file"
-.cindex "file" "journal"
-All the information Exim itself needs to set up a delivery is kept in the first
-spool file, along with the header lines. When a successful delivery occurs, the
-address is immediately written at the end of a journal file, whose name is the
-message id followed by &`-J`&. At the end of a delivery run, if there are some
-addresses left to be tried again later, the first spool file (the &`-H`& file)
-is updated to indicate which these are, and the journal file is then deleted.
-Updating the spool file is done by writing a new file and renaming it, to
-minimize the possibility of data loss.
-
-Should the system or Exim crash after a successful delivery but before
-the spool file has been updated, the journal is left lying around. The next
-time Exim attempts to deliver the message, it reads the journal file and
-updates the spool file before proceeding. This minimizes the chances of double
-deliveries caused by crashes.
-
-
-
-.section "Processing an address for delivery" "SECTprocaddress"
-.cindex "drivers" "definition of"
-.cindex "router" "definition of"
-.cindex "transport" "definition of"
-The main delivery processing elements of Exim are called &'routers'& and
-&'transports'&, and collectively these are known as &'drivers'&. Code for a
-number of them is provided in the source distribution, and compile-time options
-specify which ones are included in the binary. Runtime options specify which
-ones are actually used for delivering messages.
-
-.cindex "drivers" "instance definition"
-Each driver that is specified in the runtime configuration is an &'instance'&
-of that particular driver type. Multiple instances are allowed; for example,
-you can set up several different &(smtp)& transports, each with different
-option values that might specify different ports or different timeouts. Each
-instance has its own identifying name. In what follows we will normally use the
-instance name when discussing one particular instance (that is, one specific
-configuration of the driver), and the generic driver name when discussing
-the driver's features in general.
-
-A &'router'& is a driver that operates on an address, either determining how
-its delivery should happen, by assigning it to a specific transport, or
-converting the address into one or more new addresses (for example, via an
-alias file). A router may also explicitly choose to fail an address, causing it
-to be bounced.
-
-A &'transport'& is a driver that transmits a copy of the message from Exim's
-spool to some destination. There are two kinds of transport: for a &'local'&
-transport, the destination is a file or a pipe on the local host, whereas for a
-&'remote'& transport the destination is some other host. A message is passed
-to a specific transport as a result of successful routing. If a message has
-several recipients, it may be passed to a number of different transports.
-
-.cindex "preconditions" "definition of"
-An address is processed by passing it to each configured router instance in
-turn, subject to certain preconditions, until a router accepts the address or
-specifies that it should be bounced. We will describe this process in more
-detail shortly. First, as a simple example, we consider how each recipient
-address in a message is processed in a small configuration of three routers.
-
-To make this a more concrete example, it is described in terms of some actual
-routers, but remember, this is only an example. You can configure Exim's
-routers in many different ways, and there may be any number of routers in a
-configuration.
-
-The first router that is specified in a configuration is often one that handles
-addresses in domains that are not recognized specifically by the local host.
-Typically these are addresses for arbitrary domains on the Internet. A precondition
-is set up which looks for the special domains known to the host (for example,
-its own domain name), and the router is run for addresses that do &'not'&
-match. Typically, this is a router that looks up domains in the DNS in order to
-find the hosts to which this address routes. If it succeeds, the address is
-assigned to a suitable SMTP transport; if it does not succeed, the router is
-configured to fail the address.
-
-The second router is reached only when the domain is recognized as one that
-&"belongs"& to the local host. This router does redirection &-- also known as
-aliasing and forwarding. When it generates one or more new addresses from the
-original, each of them is routed independently from the start. Otherwise, the
-router may cause an address to fail, or it may simply decline to handle the
-address, in which case the address is passed to the next router.
-
-The final router in many configurations is one that checks to see if the
-address belongs to a local mailbox. The precondition may involve a check to
-see if the local part is the name of a login account, or it may look up the
-local part in a file or a database. If its preconditions are not met, or if
-the router declines, we have reached the end of the routers. When this happens,
-the address is bounced.
-
-
-
-.section "Processing an address for verification" "SECID16"
-.cindex "router" "for verification"
-.cindex "verifying address" "overview"
-As well as being used to decide how to deliver to an address, Exim's routers
-are also used for &'address verification'&. Verification can be requested as
-one of the checks to be performed in an ACL for incoming messages, on both
-sender and recipient addresses, and it can be tested using the &%-bv%& and
-&%-bvs%& command line options.
-
-When an address is being verified, the routers are run in &"verify mode"&. This
-does not affect the way the routers work, but it is a state that can be
-detected. By this means, a router can be skipped or made to behave differently
-when verifying. A common example is a configuration in which the first router
-sends all messages to a message-scanning program unless they have been
-previously scanned. Thus, the first router accepts all addresses without any
-checking, making it useless for verifying. Normally, the &%no_verify%& option
-would be set for such a router, causing it to be skipped in verify mode.
-
-
-
-
-.section "Running an individual router" "SECTrunindrou"
-.cindex "router" "running details"
-.cindex "preconditions" "checking"
-.cindex "router" "result of running"
-As explained in the example above, a number of preconditions are checked before
-running a router. If any are not met, the router is skipped, and the address is
-passed to the next router. When all the preconditions on a router &'are'& met,
-the router is run. What happens next depends on the outcome, which is one of
-the following:
-
-.ilist
-&'accept'&: The router accepts the address, and either assigns it to a
-transport or generates one or more &"child"& addresses. Processing the
-original address ceases
-.oindex "&%unseen%&"
-unless the &%unseen%& option is set on the router. This option
-can be used to set up multiple deliveries with different routing (for example,
-for keeping archive copies of messages). When &%unseen%& is set, the address is
-passed to the next router. Normally, however, an &'accept'& return marks the
-end of routing.
-
-Any child addresses generated by the router are processed independently,
-starting with the first router by default. It is possible to change this by
-setting the &%redirect_router%& option to specify which router to start at for
-child addresses. Unlike &%pass_router%& (see below) the router specified by
-&%redirect_router%& may be anywhere in the router configuration.
-.next
-&'pass'&: The router recognizes the address, but cannot handle it itself. It
-requests that the address be passed to another router. By default, the address
-is passed to the next router, but this can be changed by setting the
-&%pass_router%& option. However, (unlike &%redirect_router%&) the named router
-must be below the current router (to avoid loops).
-.next
-&'decline'&: The router declines to accept the address because it does not
-recognize it at all. By default, the address is passed to the next router, but
-this can be prevented by setting the &%no_more%& option. When &%no_more%& is
-set, all the remaining routers are skipped. In effect, &%no_more%& converts
-&'decline'& into &'fail'&.
-.next
-&'fail'&: The router determines that the address should fail, and queues it for
-the generation of a bounce message. There is no further processing of the
-original address unless &%unseen%& is set on the router.
-.next
-&'defer'&: The router cannot handle the address at the present time. (A
-database may be offline, or a DNS lookup may have timed out.) No further
-processing of the address happens in this delivery attempt. It is tried again
-next time the message is considered for delivery.
-.next
-&'error'&: There is some error in the router (for example, a syntax error in
-its configuration). The action is as for defer.
-.endlist
-
-If an address reaches the end of the routers without having been accepted by
-any of them, it is bounced as unrouteable. The default error message in this
-situation is &"unrouteable address"&, but you can set your own message by
-making use of the &%cannot_route_message%& option. This can be set for any
-router; the value from the last router that &"saw"& the address is used.
-
-Sometimes while routing you want to fail a delivery when some conditions are
-met but others are not, instead of passing the address on for further routing.
-You can do this by having a second router that explicitly fails the delivery
-when the relevant conditions are met. The &(redirect)& router has a &"fail"&
-facility for this purpose.
-
-
-.section "Duplicate addresses" "SECID17"
-.cindex "case of local parts"
-.cindex "address duplicate, discarding"
-.cindex "duplicate addresses"
-Once routing is complete, Exim scans the addresses that are assigned to local
-and remote transports and discards any duplicates that it finds. During this
-check, local parts are treated case-sensitively. This happens only when
-actually delivering a message; when testing routers with &%-bt%&, all the
-routed addresses are shown.
-
-
-
-.section "Router preconditions" "SECTrouprecon"
-.cindex "router" "preconditions, order of processing"
-.cindex "preconditions" "order of processing"
-The preconditions that are tested for each router are listed below, in the
-order in which they are tested. The individual configuration options are
-described in more detail in chapter &<<CHAProutergeneric>>&.
-
-.ilist
-.cindex affix "router precondition"
-The &%local_part_prefix%& and &%local_part_suffix%& options can specify that
-the local parts handled by the router may or must have certain prefixes and/or
-suffixes. If a mandatory affix (prefix or suffix) is not present, the router is
-skipped. These conditions are tested first. When an affix is present, it is
-removed from the local part before further processing, including the evaluation
-of any other conditions.
-.next
-Routers can be designated for use only when not verifying an address, that is,
-only when routing it for delivery (or testing its delivery routing). If the
-&%verify%& option is set false, the router is skipped when Exim is verifying an
-address.
-Setting the &%verify%& option actually sets two options, &%verify_sender%& and
-&%verify_recipient%&, which independently control the use of the router for
-sender and recipient verification. You can set these options directly if
-you want a router to be used for only one type of verification.
-Note that cutthrough delivery is classed as a recipient verification for this purpose.
-.next
-If the &%address_test%& option is set false, the router is skipped when Exim is
-run with the &%-bt%& option to test an address routing. This can be helpful
-when the first router sends all new messages to a scanner of some sort; it
-makes it possible to use &%-bt%& to test subsequent delivery routing without
-having to simulate the effect of the scanner.
-.next
-Routers can be designated for use only when verifying an address, as
-opposed to routing it for delivery. The &%verify_only%& option controls this.
-Again, cutthrough delivery counts as a verification.
-.next
-Individual routers can be explicitly skipped when running the routers to
-check an address given in the SMTP EXPN command (see the &%expn%& option).
-.next
-If the &%domains%& option is set, the domain of the address must be in the set
-of domains that it defines.
-.next
-.vindex "&$local_part_prefix$&"
-.vindex "&$local_part_prefix_v$&"
-.vindex "&$local_part$&"
-.vindex "&$local_part_suffix$&"
-.vindex "&$local_part_suffix_v$&"
-.cindex affix "router precondition"
-If the &%local_parts%& option is set, the local part of the address must be in
-the set of local parts that it defines. If &%local_part_prefix%& or
-&%local_part_suffix%& is in use, the prefix or suffix is removed from the local
-part before this check. If you want to do precondition tests on local parts
-that include affixes, you can do so by using a &%condition%& option (see below)
-.new
-that uses the variables &$local_part$&, &$local_part_prefix$&,
-&$local_part_prefix_v$&, &$local_part_suffix$&
-and &$local_part_suffix_v$& as necessary.
-.wen
-.next
-.vindex "&$local_user_uid$&"
-.vindex "&$local_user_gid$&"
-.vindex "&$home$&"
-If the &%check_local_user%& option is set, the local part must be the name of
-an account on the local host. If this check succeeds, the uid and gid of the
-local user are placed in &$local_user_uid$& and &$local_user_gid$& and the
-user's home directory is placed in &$home$&; these values can be used in the
-remaining preconditions.
-.next
-If the &%router_home_directory%& option is set, it is expanded at this point,
-because it overrides the value of &$home$&. If this expansion were left till
-later, the value of &$home$& as set by &%check_local_user%& would be used in
-subsequent tests. Having two different values of &$home$& in the same router
-could lead to confusion.
-.next
-If the &%senders%& option is set, the envelope sender address must be in the
-set of addresses that it defines.
-.next
-If the &%require_files%& option is set, the existence or non-existence of
-specified files is tested.
-.next
-.cindex "customizing" "precondition"
-If the &%condition%& option is set, it is evaluated and tested. This option
-uses an expanded string to allow you to set up your own custom preconditions.
-Expanded strings are described in chapter &<<CHAPexpand>>&.
-.endlist
-
-
-Note that &%require_files%& comes near the end of the list, so you cannot use
-it to check for the existence of a file in which to lookup up a domain, local
-part, or sender. However, as these options are all expanded, you can use the
-&%exists%& expansion condition to make such tests within each condition. The
-&%require_files%& option is intended for checking files that the router may be
-going to use internally, or which are needed by a specific transport (for
-example, &_.procmailrc_&).
-
-
-
-.section "Delivery in detail" "SECID18"
-.cindex "delivery" "in detail"
-When a message is to be delivered, the sequence of events is as follows:
-
-.ilist
-If a system-wide filter file is specified, the message is passed to it. The
-filter may add recipients to the message, replace the recipients, discard the
-message, cause a new message to be generated, or cause the message delivery to
-fail. The format of the system filter file is the same as for Exim user filter
-files, described in the separate document entitled &'Exim's interfaces to mail
-filtering'&.
-.cindex "Sieve filter" "not available for system filter"
-(&*Note*&: Sieve cannot be used for system filter files.)
-
-Some additional features are available in system filters &-- see chapter
-&<<CHAPsystemfilter>>& for details. Note that a message is passed to the system
-filter only once per delivery attempt, however many recipients it has. However,
-if there are several delivery attempts because one or more addresses could not
-be immediately delivered, the system filter is run each time. The filter
-condition &%first_delivery%& can be used to detect the first run of the system
-filter.
-.next
-Each recipient address is offered to each configured router, in turn, subject to
-its preconditions, until one is able to handle it. If no router can handle the
-address, that is, if they all decline, the address is failed. Because routers
-can be targeted at particular domains, several locally handled domains can be
-processed entirely independently of each other.
-.next
-.cindex "routing" "loops in"
-.cindex "loop" "while routing"
-A router that accepts an address may assign it to a local or a remote
-transport. However, the transport is not run at this time. Instead, the address
-is placed on a list for the particular transport, which will be run later.
-Alternatively, the router may generate one or more new addresses (typically
-from alias, forward, or filter files). New addresses are fed back into this
-process from the top, but in order to avoid loops, a router ignores any address
-which has an identically-named ancestor that was processed by itself.
-.next
-When all the routing has been done, addresses that have been successfully
-handled are passed to their assigned transports. When local transports are
-doing real local deliveries, they handle only one address at a time, but if a
-local transport is being used as a pseudo-remote transport (for example, to
-collect batched SMTP messages for transmission by some other means) multiple
-addresses can be handled. Remote transports can always handle more than one
-address at a time, but can be configured not to do so, or to restrict multiple
-addresses to the same domain.
-.next
-Each local delivery to a file or a pipe runs in a separate process under a
-non-privileged uid, and these deliveries are run one at a time. Remote
-deliveries also run in separate processes, normally under a uid that is private
-to Exim (&"the Exim user"&), but in this case, several remote deliveries can be
-run in parallel. The maximum number of simultaneous remote deliveries for any
-one message is set by the &%remote_max_parallel%& option.
-The order in which deliveries are done is not defined, except that all local
-deliveries happen before any remote deliveries.
-.next
-.cindex "queue runner"
-When it encounters a local delivery during a queue run, Exim checks its retry
-database to see if there has been a previous temporary delivery failure for the
-address before running the local transport. If there was a previous failure,
-Exim does not attempt a new delivery until the retry time for the address is
-reached. However, this happens only for delivery attempts that are part of a
-queue run. Local deliveries are always attempted when delivery immediately
-follows message reception, even if retry times are set for them. This makes for
-better behaviour if one particular message is causing problems (for example,
-causing quota overflow, or provoking an error in a filter file).
-.next
-.cindex "delivery" "retry in remote transports"
-Remote transports do their own retry handling, since an address may be
-deliverable to one of a number of hosts, each of which may have a different
-retry time. If there have been previous temporary failures and no host has
-reached its retry time, no delivery is attempted, whether in a queue run or
-not. See chapter &<<CHAPretry>>& for details of retry strategies.
-.next
-If there were any permanent errors, a bounce message is returned to an
-appropriate address (the sender in the common case), with details of the error
-for each failing address. Exim can be configured to send copies of bounce
-messages to other addresses.
-.next
-.cindex "delivery" "deferral"
-If one or more addresses suffered a temporary failure, the message is left on
-the queue, to be tried again later. Delivery of these addresses is said to be
-&'deferred'&.
-.next
-When all the recipient addresses have either been delivered or bounced,
-handling of the message is complete. The spool files and message log are
-deleted, though the message log can optionally be preserved if required.
-.endlist
-
-
-
-
-.section "Retry mechanism" "SECID19"
-.cindex "delivery" "retry mechanism"
-.cindex "retry" "description of mechanism"
-.cindex "queue runner"
-Exim's mechanism for retrying messages that fail to get delivered at the first
-attempt is the queue runner process. You must either run an Exim daemon that
-uses the &%-q%& option with a time interval to start queue runners at regular
-intervals or use some other means (such as &'cron'&) to start them. If you do
-not arrange for queue runners to be run, messages that fail temporarily at the
-first attempt will remain in your queue forever. A queue runner process works
-its way through the queue, one message at a time, trying each delivery that has
-passed its retry time.
-You can run several queue runners at once.
-
-Exim uses a set of configured rules to determine when next to retry the failing
-address (see chapter &<<CHAPretry>>&). These rules also specify when Exim
-should give up trying to deliver to the address, at which point it generates a
-bounce message. If no retry rules are set for a particular host, address, and
-error combination, no retries are attempted, and temporary errors are treated
-as permanent.
-
-
-
-.section "Temporary delivery failure" "SECID20"
-.cindex "delivery" "temporary failure"
-There are many reasons why a message may not be immediately deliverable to a
-particular address. Failure to connect to a remote machine (because it, or the
-connection to it, is down) is one of the most common. Temporary failures may be
-detected during routing as well as during the transport stage of delivery.
-Local deliveries may be delayed if NFS files are unavailable, or if a mailbox
-is on a file system where the user is over quota. Exim can be configured to
-impose its own quotas on local mailboxes; where system quotas are set they will
-also apply.
-
-If a host is unreachable for a period of time, a number of messages may be
-waiting for it by the time it recovers, and sending them in a single SMTP
-connection is clearly beneficial. Whenever a delivery to a remote host is
-deferred,
-.cindex "hints database" "deferred deliveries"
-Exim makes a note in its hints database, and whenever a successful
-SMTP delivery has happened, it looks to see if any other messages are waiting
-for the same host. If any are found, they are sent over the same SMTP
-connection, subject to a configuration limit as to the maximum number in any
-one connection.
-
-
-
-.section "Permanent delivery failure" "SECID21"
-.cindex "delivery" "permanent failure"
-.cindex "bounce message" "when generated"
-When a message cannot be delivered to some or all of its intended recipients, a
-bounce message is generated. Temporary delivery failures turn into permanent
-errors when their timeout expires. All the addresses that fail in a given
-delivery attempt are listed in a single message. If the original message has
-many recipients, it is possible for some addresses to fail in one delivery
-attempt and others to fail subsequently, giving rise to more than one bounce
-message. The wording of bounce messages can be customized by the administrator.
-See chapter &<<CHAPemsgcust>>& for details.
-
-.cindex "&'X-Failed-Recipients:'& header line"
-Bounce messages contain an &'X-Failed-Recipients:'& header line that lists the
-failed addresses, for the benefit of programs that try to analyse such messages
-automatically.
-
-.cindex "bounce message" "recipient of"
-A bounce message is normally sent to the sender of the original message, as
-obtained from the message's envelope. For incoming SMTP messages, this is the
-address given in the MAIL command. However, when an address is expanded via a
-forward or alias file, an alternative address can be specified for delivery
-failures of the generated addresses. For a mailing list expansion (see section
-&<<SECTmailinglists>>&) it is common to direct bounce messages to the manager
-of the list.
-
-
-
-.section "Failures to deliver bounce messages" "SECID22"
-.cindex "bounce message" "failure to deliver"
-If a bounce message (either locally generated or received from a remote host)
-itself suffers a permanent delivery failure, the message is left in the queue,
-but it is frozen, awaiting the attention of an administrator. There are options
-that can be used to make Exim discard such failed messages, or to keep them
-for only a short time (see &%timeout_frozen_after%& and
-&%ignore_bounce_errors_after%&).
-
-
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "Building and installing Exim" "CHID3"
-.scindex IIDbuex "building Exim"
-
-.section "Unpacking" "SECID23"
-Exim is distributed as a gzipped or bzipped tar file which, when unpacked,
-creates a directory with the name of the current release (for example,
-&_exim-&version()_&) into which the following files are placed:
-
-.table2 140pt
-.irow &_ACKNOWLEDGMENTS_& "contains some acknowledgments"
-.irow &_CHANGES_&         "contains a reference to where changes are &&&
-  documented"
-.irow &_LICENCE_&         "the GNU General Public Licence"
-.irow &_Makefile_&        "top-level make file"
-.irow &_NOTICE_&          "conditions for the use of Exim"
-.irow &_README_&          "list of files, directories and simple build &&&
-  instructions"
-.endtable
-
-Other files whose names begin with &_README_& may also be present. The
-following subdirectories are created:
-
-.table2 140pt
-.irow &_Local_&           "an empty directory for local configuration files"
-.irow &_OS_&              "OS-specific files"
-.irow &_doc_&             "documentation files"
-.irow &_exim_monitor_&    "source files for the Exim monitor"
-.irow &_scripts_&         "scripts used in the build process"
-.irow &_src_&             "remaining source files"
-.irow &_util_&            "independent utilities"
-.endtable
-
-The main utility programs are contained in the &_src_& directory and are built
-with the Exim binary. The &_util_& directory contains a few optional scripts
-that may be useful to some sites.
-
-
-.section "Multiple machine architectures and operating systems" "SECID24"
-.cindex "building Exim" "multiple OS/architectures"
-The building process for Exim is arranged to make it easy to build binaries for
-a number of different architectures and operating systems from the same set of
-source files. Compilation does not take place in the &_src_& directory.
-Instead, a &'build directory'& is created for each architecture and operating
-system.
-.cindex "symbolic link" "to build directory"
-Symbolic links to the sources are installed in this directory, which is where
-the actual building takes place. In most cases, Exim can discover the machine
-architecture and operating system for itself, but the defaults can be
-overridden if necessary.
-.cindex compiler requirements
-.cindex compiler version
-A C99-capable compiler will be required for the build.
-
-
-.section "PCRE library" "SECTpcre"
-.cindex "PCRE library"
-Exim no longer has an embedded PCRE library as the vast majority of
-modern systems include PCRE as a system library, although you may need to
-install the PCRE package or the PCRE development package for your operating
-system. If your system has a normal PCRE installation the Exim build
-process will need no further configuration. If the library or the
-headers are in an unusual location you will need to either set the PCRE_LIBS
-and INCLUDE directives appropriately,
-or set PCRE_CONFIG=yes to use the installed &(pcre-config)& command.
-If your operating system has no
-PCRE support then you will need to obtain and build the current PCRE
-from &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/).
-More information on PCRE is available at &url(https://www.pcre.org/).
-
-.section "DBM libraries" "SECTdb"
-.cindex "DBM libraries" "discussion of"
-.cindex "hints database" "DBM files used for"
-Even if you do not use any DBM files in your configuration, Exim still needs a
-DBM library in order to operate, because it uses indexed files for its hints
-databases. Unfortunately, there are a number of DBM libraries in existence, and
-different operating systems often have different ones installed.
-
-.cindex "Solaris" "DBM library for"
-.cindex "IRIX, DBM library for"
-.cindex "BSD, DBM library for"
-.cindex "Linux, DBM library for"
-If you are using Solaris, IRIX, one of the modern BSD systems, or a modern
-Linux distribution, the DBM configuration should happen automatically, and you
-may be able to ignore this section. Otherwise, you may have to learn more than
-you would like about DBM libraries from what follows.
-
-.cindex "&'ndbm'& DBM library"
-Licensed versions of Unix normally contain a library of DBM functions operating
-via the &'ndbm'& interface, and this is what Exim expects by default. Free
-versions of Unix seem to vary in what they contain as standard. In particular,
-some early versions of Linux have no default DBM library, and different
-distributors have chosen to bundle different libraries with their packaged
-versions. However, the more recent releases seem to have standardized on the
-Berkeley DB library.
-
-Different DBM libraries have different conventions for naming the files they
-use. When a program opens a file called &_dbmfile_&, there are several
-possibilities:
-
-.olist
-A traditional &'ndbm'& implementation, such as that supplied as part of
-Solaris, operates on two files called &_dbmfile.dir_& and &_dbmfile.pag_&.
-.next
-.cindex "&'gdbm'& DBM library"
-The GNU library, &'gdbm'&, operates on a single file. If used via its &'ndbm'&
-compatibility interface it makes two different hard links to it with names
-&_dbmfile.dir_& and &_dbmfile.pag_&, but if used via its native interface, the
-filename is used unmodified.
-.next
-.cindex "Berkeley DB library"
-The Berkeley DB package, if called via its &'ndbm'& compatibility interface,
-operates on a single file called &_dbmfile.db_&, but otherwise looks to the
-programmer exactly the same as the traditional &'ndbm'& implementation.
-.next
-If the Berkeley package is used in its native mode, it operates on a single
-file called &_dbmfile_&; the programmer's interface is somewhat different to
-the traditional &'ndbm'& interface.
-.next
-To complicate things further, there are several very different versions of the
-Berkeley DB package. Version 1.85 was stable for a very long time, releases
-2.&'x'& and 3.&'x'& were current for a while, but the latest versions when Exim last revamped support were numbered 4.&'x'&.
-Maintenance of some of the earlier releases has ceased. All versions of
-Berkeley DB could be obtained from
-&url(http://www.sleepycat.com/), which is now a redirect to their new owner's
-page with far newer versions listed.
-It is probably wise to plan to move your storage configurations away from
-Berkeley DB format, as today there are smaller and simpler alternatives more
-suited to Exim's usage model.
-.next
-.cindex "&'tdb'& DBM library"
-Yet another DBM library, called &'tdb'&, is available from
-&url(https://sourceforge.net/projects/tdb/files/). It has its own interface, and also
-operates on a single file.
-.endlist
-
-.cindex "USE_DB"
-.cindex "DBM libraries" "configuration for building"
-Exim and its utilities can be compiled to use any of these interfaces. In order
-to use any version of the Berkeley DB package in native mode, you must set
-USE_DB in an appropriate configuration file (typically
-&_Local/Makefile_&). For example:
-.code
-USE_DB=yes
-.endd
-Similarly, for gdbm you set USE_GDBM, and for tdb you set USE_TDB. An
-error is diagnosed if you set more than one of these.
-
-At the lowest level, the build-time configuration sets none of these options,
-thereby assuming an interface of type (1). However, some operating system
-configuration files (for example, those for the BSD operating systems and
-Linux) assume type (4) by setting USE_DB as their default, and the
-configuration files for Cygwin set USE_GDBM. Anything you set in
-&_Local/Makefile_&, however, overrides these system defaults.
-
-As well as setting USE_DB, USE_GDBM, or USE_TDB, it may also be
-necessary to set DBMLIB, to cause inclusion of the appropriate library, as
-in one of these lines:
-.code
-DBMLIB = -ldb
-DBMLIB = -ltdb
-.endd
-Settings like that will work if the DBM library is installed in the standard
-place. Sometimes it is not, and the library's header file may also not be in
-the default path. You may need to set INCLUDE to specify where the header
-file is, and to specify the path to the library more fully in DBMLIB, as in
-this example:
-.code
-INCLUDE=-I/usr/local/include/db-4.1
-DBMLIB=/usr/local/lib/db-4.1/libdb.a
-.endd
-There is further detailed discussion about the various DBM libraries in the
-file &_doc/dbm.discuss.txt_& in the Exim distribution.
-
-
-
-.section "Pre-building configuration" "SECID25"
-.cindex "building Exim" "pre-building configuration"
-.cindex "configuration for building Exim"
-.cindex "&_Local/Makefile_&"
-.cindex "&_src/EDITME_&"
-Before building Exim, a local configuration file that specifies options
-independent of any operating system has to be created with the name
-&_Local/Makefile_&. A template for this file is supplied as the file
-&_src/EDITME_&, and it contains full descriptions of all the option settings
-therein. These descriptions are therefore not repeated here. If you are
-building Exim for the first time, the simplest thing to do is to copy
-&_src/EDITME_& to &_Local/Makefile_&, then read it and edit it appropriately.
-
-There are three settings that you must supply, because Exim will not build
-without them. They are the location of the runtime configuration file
-(CONFIGURE_FILE), the directory in which Exim binaries will be installed
-(BIN_DIRECTORY), and the identity of the Exim user (EXIM_USER and
-maybe EXIM_GROUP as well). The value of CONFIGURE_FILE can in fact be
-a colon-separated list of filenames; Exim uses the first of them that exists.
-
-There are a few other parameters that can be specified either at build time or
-at runtime, to enable the same binary to be used on a number of different
-machines. However, if the locations of Exim's spool directory and log file
-directory (if not within the spool directory) are fixed, it is recommended that
-you specify them in &_Local/Makefile_& instead of at runtime, so that errors
-detected early in Exim's execution (such as a malformed configuration file) can
-be logged.
-
-.cindex "content scanning" "specifying at build time"
-Exim's interfaces for calling virus and spam scanning software directly from
-access control lists are not compiled by default. If you want to include these
-facilities, you need to set
-.code
-WITH_CONTENT_SCAN=yes
-.endd
-in your &_Local/Makefile_&. For details of the facilities themselves, see
-chapter &<<CHAPexiscan>>&.
-
-
-.cindex "&_Local/eximon.conf_&"
-.cindex "&_exim_monitor/EDITME_&"
-If you are going to build the Exim monitor, a similar configuration process is
-required. The file &_exim_monitor/EDITME_& must be edited appropriately for
-your installation and saved under the name &_Local/eximon.conf_&. If you are
-happy with the default settings described in &_exim_monitor/EDITME_&,
-&_Local/eximon.conf_& can be empty, but it must exist.
-
-This is all the configuration that is needed in straightforward cases for known
-operating systems. However, the building process is set up so that it is easy
-to override options that are set by default or by operating-system-specific
-configuration files, for example, to change the C compiler, which
-defaults to &%gcc%&. See section &<<SECToverride>>& below for details of how to
-do this.
-
-
-
-.section "Support for iconv()" "SECID26"
-.cindex "&[iconv()]& support"
-.cindex "RFC 2047"
-The contents of header lines in messages may be encoded according to the rules
-described RFC 2047. This makes it possible to transmit characters that are not
-in the ASCII character set, and to label them as being in a particular
-character set. When Exim is inspecting header lines by means of the &%$h_%&
-mechanism, it decodes them, and translates them into a specified character set
-(default is set at build time). The translation is possible only if the operating system
-supports the &[iconv()]& function.
-
-However, some of the operating systems that supply &[iconv()]& do not support
-very many conversions. The GNU &%libiconv%& library (available from
-&url(https://www.gnu.org/software/libiconv/)) can be installed on such
-systems to remedy this deficiency, as well as on systems that do not supply
-&[iconv()]& at all. After installing &%libiconv%&, you should add
-.code
-HAVE_ICONV=yes
-.endd
-to your &_Local/Makefile_& and rebuild Exim.
-
-
-
-.section "Including TLS/SSL encryption support" "SECTinctlsssl"
-.cindex "TLS" "including support for TLS"
-.cindex "encryption" "including support for"
-.cindex "OpenSSL" "building Exim with"
-.cindex "GnuTLS" "building Exim with"
-Exim is usually built to support encrypted SMTP connections, using the STARTTLS
-command as per RFC 2487. It can also support clients that expect to
-start a TLS session immediately on connection to a non-standard port (see the
-&%tls_on_connect_ports%& runtime option and the &%-tls-on-connect%& command
-line option).
-
-If you want to build Exim with TLS support, you must first install either the
-OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for
-implementing SSL.
-
-If you do not want TLS support you should set
-.code
-DISABLE_TLS=yes
-.endd
-in &_Local/Makefile_&.
-
-If OpenSSL is installed, you should set
-.code
-USE_OPENSL=yes
-TLS_LIBS=-lssl -lcrypto
-.endd
-in &_Local/Makefile_&. You may also need to specify the locations of the
-OpenSSL library and include files. For example:
-.code
-USE_OPENSSL=yes
-TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
-TLS_INCLUDE=-I/usr/local/openssl/include/
-.endd
-.cindex "pkg-config" "OpenSSL"
-If you have &'pkg-config'& available, then instead you can just use:
-.code
-USE_OPENSSL=yes
-USE_OPENSSL_PC=openssl
-.endd
-.cindex "USE_GNUTLS"
-If GnuTLS is installed, you should set
-.code
-USE_GNUTLS=yes
-TLS_LIBS=-lgnutls -ltasn1 -lgcrypt
-.endd
-in &_Local/Makefile_&, and again you may need to specify the locations of the
-library and include files. For example:
-.code
-USE_GNUTLS=yes
-TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt
-TLS_INCLUDE=-I/usr/gnu/include
-.endd
-.cindex "pkg-config" "GnuTLS"
-If you have &'pkg-config'& available, then instead you can just use:
-.code
-USE_GNUTLS=yes
-USE_GNUTLS_PC=gnutls
-.endd
-
-You do not need to set TLS_INCLUDE if the relevant directory is already
-specified in INCLUDE. Details of how to configure Exim to make use of TLS are
-given in chapter &<<CHAPTLS>>&.
-
-
-
-
-.section "Use of tcpwrappers" "SECID27"
-
-.cindex "tcpwrappers, building Exim to support"
-.cindex "USE_TCP_WRAPPERS"
-.cindex "TCP_WRAPPERS_DAEMON_NAME"
-.cindex "tcp_wrappers_daemon_name"
-Exim can be linked with the &'tcpwrappers'& library in order to check incoming
-SMTP calls using the &'tcpwrappers'& control files. This may be a convenient
-alternative to Exim's own checking facilities for installations that are
-already making use of &'tcpwrappers'& for other purposes. To do this, you
-should set USE_TCP_WRAPPERS in &_Local/Makefile_&, arrange for the file
-&_tcpd.h_& to be available at compile time, and also ensure that the library
-&_libwrap.a_& is available at link time, typically by including &%-lwrap%& in
-EXTRALIBS_EXIM. For example, if &'tcpwrappers'& is installed in &_/usr/local_&,
-you might have
-.code
-USE_TCP_WRAPPERS=yes
-CFLAGS=-O -I/usr/local/include
-EXTRALIBS_EXIM=-L/usr/local/lib -lwrap
-.endd
-in &_Local/Makefile_&. The daemon name to use in the &'tcpwrappers'& control
-files is &"exim"&. For example, the line
-.code
-exim : LOCAL  192.168.1.  .friendly.domain.example
-.endd
-in your &_/etc/hosts.allow_& file allows connections from the local host, from
-the subnet 192.168.1.0/24, and from all hosts in &'friendly.domain.example'&.
-All other connections are denied. The daemon name used by &'tcpwrappers'&
-can be changed at build time by setting TCP_WRAPPERS_DAEMON_NAME in
-&_Local/Makefile_&, or by setting tcp_wrappers_daemon_name in the
-configure file. Consult the &'tcpwrappers'& documentation for
-further details.
-
-
-.section "Including support for IPv6" "SECID28"
-.cindex "IPv6" "including support for"
-Exim contains code for use on systems that have IPv6 support. Setting
-&`HAVE_IPV6=YES`& in &_Local/Makefile_& causes the IPv6 code to be included;
-it may also be necessary to set IPV6_INCLUDE and IPV6_LIBS on systems
-where the IPv6 support is not fully integrated into the normal include and
-library files.
-
-Two different types of DNS record for handling IPv6 addresses have been
-defined. AAAA records (analogous to A records for IPv4) are in use, and are
-currently seen as the mainstream. Another record type called A6 was proposed
-as better than AAAA because it had more flexibility. However, it was felt to be
-over-complex, and its status was reduced to &"experimental"&.
-Exim used to
-have a compile option for including A6 record support but this has now been
-withdrawn.
-
-
-
-.section "Dynamically loaded lookup module support" "SECTdynamicmodules"
-.cindex "lookup modules"
-.cindex "dynamic modules"
-.cindex ".so building"
-On some platforms, Exim supports not compiling all lookup types directly into
-the main binary, instead putting some into external modules which can be loaded
-on demand.
-This permits packagers to build Exim with support for lookups with extensive
-library dependencies without requiring all users to install all of those
-dependencies.
-Most, but not all, lookup types can be built this way.
-
-Set &`LOOKUP_MODULE_DIR`& to the directory into which the modules will be
-installed; Exim will only load modules from that directory, as a security
-measure.  You will need to set &`CFLAGS_DYNAMIC`& if not already defined
-for your OS; see &_OS/Makefile-Linux_& for an example.
-Some other requirements for adjusting &`EXTRALIBS`& may also be necessary,
-see &_src/EDITME_& for details.
-
-Then, for each module to be loaded dynamically, define the relevant
-&`LOOKUP_`&<&'lookup_type'&> flags to have the value "2" instead of "yes".
-For example, this will build in lsearch but load sqlite and mysql support
-on demand:
-.code
-LOOKUP_LSEARCH=yes
-LOOKUP_SQLITE=2
-LOOKUP_MYSQL=2
-.endd
-
-
-.section "The building process" "SECID29"
-.cindex "build directory"
-Once &_Local/Makefile_& (and &_Local/eximon.conf_&, if required) have been
-created, run &'make'& at the top level. It determines the architecture and
-operating system types, and creates a build directory if one does not exist.
-For example, on a Sun system running Solaris 8, the directory
-&_build-SunOS5-5.8-sparc_& is created.
-.cindex "symbolic link" "to source files"
-Symbolic links to relevant source files are installed in the build directory.
-
-If this is the first time &'make'& has been run, it calls a script that builds
-a make file inside the build directory, using the configuration files from the
-&_Local_& directory. The new make file is then passed to another instance of
-&'make'&. This does the real work, building a number of utility scripts, and
-then compiling and linking the binaries for the Exim monitor (if configured), a
-number of utility programs, and finally Exim itself. The command &`make
-makefile`& can be used to force a rebuild of the make file in the build
-directory, should this ever be necessary.
-
-If you have problems building Exim, check for any comments there may be in the
-&_README_& file concerning your operating system, and also take a look at the
-FAQ, where some common problems are covered.
-
-
-
-.section 'Output from &"make"&' "SECID283"
-The output produced by the &'make'& process for compile lines is often very
-unreadable, because these lines can be very long. For this reason, the normal
-output is suppressed by default, and instead output similar to that which
-appears when compiling the 2.6 Linux kernel is generated: just a short line for
-each module that is being compiled or linked. However, it is still possible to
-get the full output, by calling &'make'& like this:
-.code
-FULLECHO='' make -e
-.endd
-The value of FULLECHO defaults to &"@"&, the flag character that suppresses
-command reflection in &'make'&. When you ask for the full output, it is
-given in addition to the short output.
-
-
-
-.section "Overriding build-time options for Exim" "SECToverride"
-.cindex "build-time options, overriding"
-The main make file that is created at the beginning of the building process
-consists of the concatenation of a number of files which set configuration
-values, followed by a fixed set of &'make'& instructions. If a value is set
-more than once, the last setting overrides any previous ones. This provides a
-convenient way of overriding defaults. The files that are concatenated are, in
-order:
-.display
-&_OS/Makefile-Default_&
-&_OS/Makefile-_&<&'ostype'&>
-&_Local/Makefile_&
-&_Local/Makefile-_&<&'ostype'&>
-&_Local/Makefile-_&<&'archtype'&>
-&_Local/Makefile-_&<&'ostype'&>-<&'archtype'&>
-&_OS/Makefile-Base_&
-.endd
-.cindex "&_Local/Makefile_&"
-.cindex "building Exim" "operating system type"
-.cindex "building Exim" "architecture type"
-where <&'ostype'&> is the operating system type and <&'archtype'&> is the
-architecture type. &_Local/Makefile_& is required to exist, and the building
-process fails if it is absent. The other three &_Local_& files are optional,
-and are often not needed.
-
-The values used for <&'ostype'&> and <&'archtype'&> are obtained from scripts
-called &_scripts/os-type_& and &_scripts/arch-type_& respectively. If either of
-the environment variables EXIM_OSTYPE or EXIM_ARCHTYPE is set, their
-values are used, thereby providing a means of forcing particular settings.
-Otherwise, the scripts try to get values from the &%uname%& command. If this
-fails, the shell variables OSTYPE and ARCHTYPE are inspected. A number
-of &'ad hoc'& transformations are then applied, to produce the standard names
-that Exim expects. You can run these scripts directly from the shell in order
-to find out what values are being used on your system.
-
-
-&_OS/Makefile-Default_& contains comments about the variables that are set
-therein. Some (but not all) are mentioned below. If there is something that
-needs changing, review the contents of this file and the contents of the make
-file for your operating system (&_OS/Makefile-<ostype>_&) to see what the
-default values are.
-
-
-.cindex "building Exim" "overriding default settings"
-If you need to change any of the values that are set in &_OS/Makefile-Default_&
-or in &_OS/Makefile-<ostype>_&, or to add any new definitions, you do not
-need to change the original files. Instead, you should make the changes by
-putting the new values in an appropriate &_Local_& file. For example,
-.cindex "Tru64-Unix build-time settings"
-when building Exim in many releases of the Tru64-Unix (formerly Digital UNIX,
-formerly DEC-OSF1) operating system, it is necessary to specify that the C
-compiler is called &'cc'& rather than &'gcc'&. Also, the compiler must be
-called with the option &%-std1%&, to make it recognize some of the features of
-Standard C that Exim uses. (Most other compilers recognize Standard C by
-default.) To do this, you should create a file called &_Local/Makefile-OSF1_&
-containing the lines
-.code
-CC=cc
-CFLAGS=-std1
-.endd
-If you are compiling for just one operating system, it may be easier to put
-these lines directly into &_Local/Makefile_&.
-
-Keeping all your local configuration settings separate from the distributed
-files makes it easy to transfer them to new versions of Exim simply by copying
-the contents of the &_Local_& directory.
-
-
-.cindex "NIS lookup type" "including support for"
-.cindex "NIS+ lookup type" "including support for"
-.cindex "LDAP" "including support for"
-.cindex "lookup" "inclusion in binary"
-Exim contains support for doing LDAP, NIS, NIS+, and other kinds of file
-lookup, but not all systems have these components installed, so the default is
-not to include the relevant code in the binary. All the different kinds of file
-and database lookup that Exim supports are implemented as separate code modules
-which are included only if the relevant compile-time options are set. In the
-case of LDAP, NIS, and NIS+, the settings for &_Local/Makefile_& are:
-.code
-LOOKUP_LDAP=yes
-LOOKUP_NIS=yes
-LOOKUP_NISPLUS=yes
-.endd
-and similar settings apply to the other lookup types. They are all listed in
-&_src/EDITME_&. In many cases the relevant include files and interface
-libraries need to be installed before compiling Exim.
-.cindex "cdb" "including support for"
-However, there are some optional lookup types (such as cdb) for which
-the code is entirely contained within Exim, and no external include
-files or libraries are required. When a lookup type is not included in the
-binary, attempts to configure Exim to use it cause runtime configuration
-errors.
-
-.cindex "pkg-config" "lookups"
-.cindex "pkg-config" "authenticators"
-Many systems now use a tool called &'pkg-config'& to encapsulate information
-about how to compile against a library; Exim has some initial support for
-being able to use pkg-config for lookups and authenticators.  For any given
-makefile variable which starts &`LOOKUP_`& or &`AUTH_`&, you can add a new
-variable with the &`_PC`& suffix in the name and assign as the value the
-name of the package to be queried.  The results of querying via the
-&'pkg-config'& command will be added to the appropriate Makefile variables
-with &`+=`& directives, so your version of &'make'& will need to support that
-syntax.  For instance:
-.code
-LOOKUP_SQLITE=yes
-LOOKUP_SQLITE_PC=sqlite3
-AUTH_GSASL=yes
-AUTH_GSASL_PC=libgsasl
-AUTH_HEIMDAL_GSSAPI=yes
-AUTH_HEIMDAL_GSSAPI_PC=heimdal-gssapi
-.endd
-
-.cindex "Perl" "including support for"
-Exim can be linked with an embedded Perl interpreter, allowing Perl
-subroutines to be called during string expansion. To enable this facility,
-.code
-EXIM_PERL=perl.o
-.endd
-must be defined in &_Local/Makefile_&. Details of this facility are given in
-chapter &<<CHAPperl>>&.
-
-.cindex "X11 libraries, location of"
-The location of the X11 libraries is something that varies a lot between
-operating systems, and there may be different versions of X11 to cope
-with. Exim itself makes no use of X11, but if you are compiling the Exim
-monitor, the X11 libraries must be available.
-The following three variables are set in &_OS/Makefile-Default_&:
-.code
-X11=/usr/X11R6
-XINCLUDE=-I$(X11)/include
-XLFLAGS=-L$(X11)/lib
-.endd
-These are overridden in some of the operating-system configuration files. For
-example, in &_OS/Makefile-SunOS5_& there is
-.code
-X11=/usr/openwin
-XINCLUDE=-I$(X11)/include
-XLFLAGS=-L$(X11)/lib -R$(X11)/lib
-.endd
-If you need to override the default setting for your operating system, place a
-definition of all three of these variables into your
-&_Local/Makefile-<ostype>_& file.
-
-.cindex "EXTRALIBS"
-If you need to add any extra libraries to the link steps, these can be put in a
-variable called EXTRALIBS, which appears in all the link commands, but by
-default is not defined. In contrast, EXTRALIBS_EXIM is used only on the
-command for linking the main Exim binary, and not for any associated utilities.
-
-.cindex "DBM libraries" "configuration for building"
-There is also DBMLIB, which appears in the link commands for binaries that
-use DBM functions (see also section &<<SECTdb>>&). Finally, there is
-EXTRALIBS_EXIMON, which appears only in the link step for the Exim monitor
-binary, and which can be used, for example, to include additional X11
-libraries.
-
-.cindex "configuration file" "editing"
-The make file copes with rebuilding Exim correctly if any of the configuration
-files are edited. However, if an optional configuration file is deleted, it is
-necessary to touch the associated non-optional file (that is,
-&_Local/Makefile_& or &_Local/eximon.conf_&) before rebuilding.
-
-
-.section "OS-specific header files" "SECID30"
-.cindex "&_os.h_&"
-.cindex "building Exim" "OS-specific C header files"
-The &_OS_& directory contains a number of files with names of the form
-&_os.h-<ostype>_&. These are system-specific C header files that should not
-normally need to be changed. There is a list of macro settings that are
-recognized in the file &_OS/os.configuring_&, which should be consulted if you
-are porting Exim to a new operating system.
-
-
-
-.section "Overriding build-time options for the monitor" "SECID31"
-.cindex "building Eximon"
-A similar process is used for overriding things when building the Exim monitor,
-where the files that are involved are
-.display
-&_OS/eximon.conf-Default_&
-&_OS/eximon.conf-_&<&'ostype'&>
-&_Local/eximon.conf_&
-&_Local/eximon.conf-_&<&'ostype'&>
-&_Local/eximon.conf-_&<&'archtype'&>
-&_Local/eximon.conf-_&<&'ostype'&>-<&'archtype'&>
-.endd
-.cindex "&_Local/eximon.conf_&"
-As with Exim itself, the final three files need not exist, and in this case the
-&_OS/eximon.conf-<ostype>_& file is also optional. The default values in
-&_OS/eximon.conf-Default_& can be overridden dynamically by setting environment
-variables of the same name, preceded by EXIMON_. For example, setting
-EXIMON_LOG_DEPTH in the environment overrides the value of
-LOG_DEPTH at runtime.
-.ecindex IIDbuex
-
-
-.section "Installing Exim binaries and scripts" "SECID32"
-.cindex "installing Exim"
-.cindex "BIN_DIRECTORY"
-The command &`make install`& runs the &(exim_install)& script with no
-arguments. The script copies binaries and utility scripts into the directory
-whose name is specified by the BIN_DIRECTORY setting in &_Local/Makefile_&.
-.cindex "setuid" "installing Exim with"
-The install script copies files only if they are newer than the files they are
-going to replace. The Exim binary is required to be owned by root and have the
-&'setuid'& bit set, for normal configurations. Therefore, you must run &`make
-install`& as root so that it can set up the Exim binary in this way. However, in
-some special situations (for example, if a host is doing no local deliveries)
-it may be possible to run Exim without making the binary setuid root (see
-chapter &<<CHAPsecurity>>& for details).
-
-.cindex "CONFIGURE_FILE"
-Exim's runtime configuration file is named by the CONFIGURE_FILE setting
-in &_Local/Makefile_&. If this names a single file, and the file does not
-exist, the default configuration file &_src/configure.default_& is copied there
-by the installation script. If a runtime configuration file already exists, it
-is left alone. If CONFIGURE_FILE is a colon-separated list, naming several
-alternative files, no default is installed.
-
-.cindex "system aliases file"
-.cindex "&_/etc/aliases_&"
-One change is made to the default configuration file when it is installed: the
-default configuration contains a router that references a system aliases file.
-The path to this file is set to the value specified by
-SYSTEM_ALIASES_FILE in &_Local/Makefile_& (&_/etc/aliases_& by default).
-If the system aliases file does not exist, the installation script creates it,
-and outputs a comment to the user.
-
-The created file contains no aliases, but it does contain comments about the
-aliases a site should normally have. Mail aliases have traditionally been
-kept in &_/etc/aliases_&. However, some operating systems are now using
-&_/etc/mail/aliases_&. You should check if yours is one of these, and change
-Exim's configuration if necessary.
-
-The default configuration uses the local host's name as the only local domain,
-and is set up to do local deliveries into the shared directory &_/var/mail_&,
-running as the local user. System aliases and &_.forward_& files in users' home
-directories are supported, but no NIS or NIS+ support is configured. Domains
-other than the name of the local host are routed using the DNS, with delivery
-over SMTP.
-
-It is possible to install Exim for special purposes (such as building a binary
-distribution) in a private part of the file system. You can do this by a
-command such as
-.code
-make DESTDIR=/some/directory/ install
-.endd
-This has the effect of pre-pending the specified directory to all the file
-paths, except the name of the system aliases file that appears in the default
-configuration. (If a default alias file is created, its name &'is'& modified.)
-For backwards compatibility, ROOT is used if DESTDIR is not set,
-but this usage is deprecated.
-
-.cindex "installing Exim" "what is not installed"
-Running &'make install'& does not copy the Exim 4 conversion script
-&'convert4r4'&. You will probably run this only once if you are
-upgrading from Exim 3. None of the documentation files in the &_doc_&
-directory are copied, except for the info files when you have set
-INFO_DIRECTORY, as described in section &<<SECTinsinfdoc>>& below.
-
-For the utility programs, old versions are renamed by adding the suffix &_.O_&
-to their names. The Exim binary itself, however, is handled differently. It is
-installed under a name that includes the version number and the compile number,
-for example, &_exim-&version()-1_&. The script then arranges for a symbolic link
-called &_exim_& to point to the binary. If you are updating a previous version
-of Exim, the script takes care to ensure that the name &_exim_& is never absent
-from the directory (as seen by other processes).
-
-.cindex "installing Exim" "testing the script"
-If you want to see what the &'make install'& will do before running it for
-real, you can pass the &%-n%& option to the installation script by this
-command:
-.code
-make INSTALL_ARG=-n install
-.endd
-The contents of the variable INSTALL_ARG are passed to the installation
-script. You do not need to be root to run this test. Alternatively, you can run
-the installation script directly, but this must be from within the build
-directory. For example, from the top-level Exim directory you could use this
-command:
-.code
-(cd build-SunOS5-5.5.1-sparc; ../scripts/exim_install -n)
-.endd
-.cindex "installing Exim" "install script options"
-There are two other options that can be supplied to the installation script.
-
-.ilist
-&%-no_chown%& bypasses the call to change the owner of the installed binary
-to root, and the call to make it a setuid binary.
-.next
-&%-no_symlink%& bypasses the setting up of the symbolic link &_exim_& to the
-installed binary.
-.endlist
-
-INSTALL_ARG can be used to pass these options to the script. For example:
-.code
-make INSTALL_ARG=-no_symlink install
-.endd
-The installation script can also be given arguments specifying which files are
-to be copied. For example, to install just the Exim binary, and nothing else,
-without creating the symbolic link, you could use:
-.code
-make INSTALL_ARG='-no_symlink exim' install
-.endd
-
-
-
-.section "Installing info documentation" "SECTinsinfdoc"
-.cindex "installing Exim" "&'info'& documentation"
-Not all systems use the GNU &'info'& system for documentation, and for this
-reason, the Texinfo source of Exim's documentation is not included in the main
-distribution. Instead it is available separately from the FTP site (see section
-&<<SECTavail>>&).
-
-If you have defined INFO_DIRECTORY in &_Local/Makefile_& and the Texinfo
-source of the documentation is found in the source tree, running &`make
-install`& automatically builds the info files and installs them.
-
-
-
-.section "Setting up the spool directory" "SECID33"
-.cindex "spool directory" "creating"
-When it starts up, Exim tries to create its spool directory if it does not
-exist. The Exim uid and gid are used for the owner and group of the spool
-directory. Sub-directories are automatically created in the spool directory as
-necessary.
-
-
-
-
-.section "Testing" "SECID34"
-.cindex "testing" "installation"
-Having installed Exim, you can check that the runtime configuration file is
-syntactically valid by running the following command, which assumes that the
-Exim binary directory is within your PATH environment variable:
-.code
-exim -bV
-.endd
-If there are any errors in the configuration file, Exim outputs error messages.
-Otherwise it outputs the version number and build date,
-the DBM library that is being used, and information about which drivers and
-other optional code modules are included in the binary.
-Some simple routing tests can be done by using the address testing option. For
-example,
-.display
-&`exim -bt`& <&'local username'&>
-.endd
-should verify that it recognizes a local mailbox, and
-.display
-&`exim -bt`& <&'remote address'&>
-.endd
-a remote one. Then try getting it to deliver mail, both locally and remotely.
-This can be done by passing messages directly to Exim, without going through a
-user agent. For example:
-.code
-exim -v postmaster@your.domain.example
-From: user@your.domain.example
-To: postmaster@your.domain.example
-Subject: Testing Exim
-
-This is a test message.
-^D
-.endd
-The &%-v%& option causes Exim to output some verification of what it is doing.
-In this case you should see copies of three log lines, one for the message's
-arrival, one for its delivery, and one containing &"Completed"&.
-
-.cindex "delivery" "problems with"
-If you encounter problems, look at Exim's log files (&'mainlog'& and
-&'paniclog'&) to see if there is any relevant information there. Another source
-of information is running Exim with debugging turned on, by specifying the
-&%-d%& option. If a message is stuck on Exim's spool, you can force a delivery
-with debugging turned on by a command of the form
-.display
-&`exim -d -M`& <&'exim-message-id'&>
-.endd
-You must be root or an &"admin user"& in order to do this. The &%-d%& option
-produces rather a lot of output, but you can cut this down to specific areas.
-For example, if you use &%-d-all+route%& only the debugging information
-relevant to routing is included. (See the &%-d%& option in chapter
-&<<CHAPcommandline>>& for more details.)
-
-.cindex '&"sticky"& bit'
-.cindex "lock files"
-One specific problem that has shown up on some sites is the inability to do
-local deliveries into a shared mailbox directory, because it does not have the
-&"sticky bit"& set on it. By default, Exim tries to create a lock file before
-writing to a mailbox file, and if it cannot create the lock file, the delivery
-is deferred. You can get round this either by setting the &"sticky bit"& on the
-directory, or by setting a specific group for local deliveries and allowing
-that group to create files in the directory (see the comments above the
-&(local_delivery)& transport in the default configuration file). Another
-approach is to configure Exim not to use lock files, but just to rely on
-&[fcntl()]& locking instead. However, you should do this only if all user
-agents also use &[fcntl()]& locking. For further discussion of locking issues,
-see chapter &<<CHAPappendfile>>&.
-
-One thing that cannot be tested on a system that is already running an MTA is
-the receipt of incoming SMTP mail on the standard SMTP port. However, the
-&%-oX%& option can be used to run an Exim daemon that listens on some other
-port, or &'inetd'& can be used to do this. The &%-bh%& option and the
-&'exim_checkaccess'& utility can be used to check out policy controls on
-incoming SMTP mail.
-
-Testing a new version on a system that is already running Exim can most easily
-be done by building a binary with a different CONFIGURE_FILE setting. From
-within the runtime configuration, all other file and directory names
-that Exim uses can be altered, in order to keep it entirely clear of the
-production version.
-
-
-.section "Replacing another MTA with Exim" "SECID35"
-.cindex "replacing another MTA"
-Building and installing Exim for the first time does not of itself put it in
-general use. The name by which the system's MTA is called by mail user agents
-is either &_/usr/sbin/sendmail_&, or &_/usr/lib/sendmail_& (depending on the
-operating system), and it is necessary to make this name point to the &'exim'&
-binary in order to get the user agents to pass messages to Exim. This is
-normally done by renaming any existing file and making &_/usr/sbin/sendmail_&
-or &_/usr/lib/sendmail_&
-.cindex "symbolic link" "to &'exim'& binary"
-a symbolic link to the &'exim'& binary. It is a good idea to remove any setuid
-privilege and executable status from the old MTA. It is then necessary to stop
-and restart the mailer daemon, if one is running.
-
-.cindex "FreeBSD, MTA indirection"
-.cindex "&_/etc/mail/mailer.conf_&"
-Some operating systems have introduced alternative ways of switching MTAs. For
-example, if you are running FreeBSD, you need to edit the file
-&_/etc/mail/mailer.conf_& instead of setting up a symbolic link as just
-described. A typical example of the contents of this file for running Exim is
-as follows:
-.code
-sendmail            /usr/exim/bin/exim
-send-mail           /usr/exim/bin/exim
-mailq               /usr/exim/bin/exim -bp
-newaliases          /usr/bin/true
-.endd
-Once you have set up the symbolic link, or edited &_/etc/mail/mailer.conf_&,
-your Exim installation is &"live"&. Check it by sending a message from your
-favourite user agent.
-
-You should consider what to tell your users about the change of MTA. Exim may
-have different capabilities to what was previously running, and there are
-various operational differences such as the text of messages produced by
-command line options and in bounce messages. If you allow your users to make
-use of Exim's filtering capabilities, you should make the document entitled
-&'Exim's interface to mail filtering'& available to them.
-
-
-
-.section "Upgrading Exim" "SECID36"
-.cindex "upgrading Exim"
-If you are already running Exim on your host, building and installing a new
-version automatically makes it available to MUAs, or any other programs that
-call the MTA directly. However, if you are running an Exim daemon, you do need
-.cindex restart "on HUP signal"
-.cindex signal "HUP, to restart"
-to send it a HUP signal, to make it re-execute itself, and thereby pick up the
-new binary. You do not need to stop processing mail in order to install a new
-version of Exim. The install script does not modify an existing runtime
-configuration file.
-
-
-
-
-.section "Stopping the Exim daemon on Solaris" "SECID37"
-.cindex "Solaris" "stopping Exim on"
-The standard command for stopping the mailer daemon on Solaris is
-.code
-/etc/init.d/sendmail stop
-.endd
-If &_/usr/lib/sendmail_& has been turned into a symbolic link, this script
-fails to stop Exim because it uses the command &'ps -e'& and greps the output
-for the text &"sendmail"&; this is not present because the actual program name
-(that is, &"exim"&) is given by the &'ps'& command with these options. A
-solution is to replace the line that finds the process id with something like
-.code
-pid=`cat /var/spool/exim/exim-daemon.pid`
-.endd
-to obtain the daemon's pid directly from the file that Exim saves it in.
-
-Note, however, that stopping the daemon does not &"stop Exim"&. Messages can
-still be received from local processes, and if automatic delivery is configured
-(the normal case), deliveries will still occur.
-
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "The Exim command line" "CHAPcommandline"
-.scindex IIDclo1 "command line" "options"
-.scindex IIDclo2 "options" "command line"
-Exim's command line takes the standard Unix form of a sequence of options,
-each starting with a hyphen character, followed by a number of arguments. The
-options are compatible with the main options of Sendmail, and there are also
-some additional options, some of which are compatible with Smail 3. Certain
-combinations of options do not make sense, and provoke an error if used.
-The form of the arguments depends on which options are set.
-
-
-.section "Setting options by program name" "SECID38"
-.cindex "&'mailq'&"
-If Exim is called under the name &'mailq'&, it behaves as if the option &%-bp%&
-were present before any other options.
-The &%-bp%& option requests a listing of the contents of the mail queue on the
-standard output.
-This feature is for compatibility with some systems that contain a command of
-that name in one of the standard libraries, symbolically linked to
-&_/usr/sbin/sendmail_& or &_/usr/lib/sendmail_&.
-
-.cindex "&'rsmtp'&"
-If Exim is called under the name &'rsmtp'& it behaves as if the option &%-bS%&
-were present before any other options, for compatibility with Smail. The
-&%-bS%& option is used for reading in a number of messages in batched SMTP
-format.
-
-.cindex "&'rmail'&"
-If Exim is called under the name &'rmail'& it behaves as if the &%-i%& and
-&%-oee%& options were present before any other options, for compatibility with
-Smail. The name &'rmail'& is used as an interface by some UUCP systems.
-
-.cindex "&'runq'&"
-.cindex "queue runner"
-If Exim is called under the name &'runq'& it behaves as if the option &%-q%&
-were present before any other options, for compatibility with Smail. The &%-q%&
-option causes a single queue runner process to be started.
-
-.cindex "&'newaliases'&"
-.cindex "alias file" "building"
-.cindex "Sendmail compatibility" "calling Exim as &'newaliases'&"
-If Exim is called under the name &'newaliases'& it behaves as if the option
-&%-bi%& were present before any other options, for compatibility with Sendmail.
-This option is used for rebuilding Sendmail's alias file. Exim does not have
-the concept of a single alias file, but can be configured to run a given
-command if called with the &%-bi%& option.
-
-
-.section "Trusted and admin users" "SECTtrustedadmin"
-Some Exim options are available only to &'trusted users'& and others are
-available only to &'admin users'&. In the description below, the phrases &"Exim
-user"& and &"Exim group"& mean the user and group defined by EXIM_USER and
-EXIM_GROUP in &_Local/Makefile_& or set by the &%exim_user%& and
-&%exim_group%& options. These do not necessarily have to use the name &"exim"&.
-
-.ilist
-.cindex "trusted users" "definition of"
-.cindex "user" "trusted definition of"
-The trusted users are root, the Exim user, any user listed in the
-&%trusted_users%& configuration option, and any user whose current group or any
-supplementary group is one of those listed in the &%trusted_groups%&
-configuration option. Note that the Exim group is not automatically trusted.
-
-.cindex '&"From"& line'
-.cindex "envelope from"
-.cindex "envelope sender"
-Trusted users are always permitted to use the &%-f%& option or a leading
-&"From&~"& line to specify the envelope sender of a message that is passed to
-Exim through the local interface (see the &%-bm%& and &%-f%& options below).
-See the &%untrusted_set_sender%& option for a way of permitting non-trusted
-users to set envelope senders.
-
-.cindex "&'From:'& header line"
-.cindex "&'Sender:'& header line"
-.cindex "header lines" "From:"
-.cindex "header lines" "Sender:"
-For a trusted user, there is never any check on the contents of the &'From:'&
-header line, and a &'Sender:'& line is never added. Furthermore, any existing
-&'Sender:'& line in incoming local (non-TCP/IP) messages is not removed.
-
-Trusted users may also specify a host name, host address, interface address,
-protocol name, ident value, and authentication data when submitting a message
-locally. Thus, they are able to insert messages into Exim's queue locally that
-have the characteristics of messages received from a remote host. Untrusted
-users may in some circumstances use &%-f%&, but can never set the other values
-that are available to trusted users.
-.next
-.cindex "user" "admin definition of"
-.cindex "admin user" "definition of"
-The admin users are root, the Exim user, and any user that is a member of the
-Exim group or of any group listed in the &%admin_groups%& configuration option.
-The current group does not have to be one of these groups.
-
-Admin users are permitted to list the queue, and to carry out certain
-operations on messages, for example, to force delivery failures. It is also
-necessary to be an admin user in order to see the full information provided by
-the Exim monitor, and full debugging output.
-
-By default, the use of the &%-M%&, &%-q%&, &%-R%&, and &%-S%& options to cause
-Exim to attempt delivery of messages on its queue is restricted to admin users.
-However, this restriction can be relaxed by setting the &%prod_requires_admin%&
-option false (that is, specifying &%no_prod_requires_admin%&).
-
-Similarly, the use of the &%-bp%& option to list all the messages in the queue
-is restricted to admin users unless &%queue_list_requires_admin%& is set
-false.
-.endlist
-
-
-&*Warning*&: If you configure your system so that admin users are able to
-edit Exim's configuration file, you are giving those users an easy way of
-getting root. There is further discussion of this issue at the start of chapter
-&<<CHAPconf>>&.
-
-
-
-
-.section "Command line options" "SECID39"
-Exim's command line options are described in alphabetical order below. If none
-of the options that specifies a specific action (such as starting the daemon or
-a queue runner, or testing an address, or receiving a message in a specific
-format, or listing the queue) are present, and there is at least one argument
-on the command line, &%-bm%& (accept a local message on the standard input,
-with the arguments specifying the recipients) is assumed. Otherwise, Exim
-outputs a brief message about itself and exits.
-
-. ////////////////////////////////////////////////////////////////////////////
-. Insert a stylized XML comment here, to identify the start of the command line
-. options. This is for the benefit of the Perl script that automatically
-. creates a man page for the options.
-. ////////////////////////////////////////////////////////////////////////////
-
-.literal xml
-<!-- === Start of command line options === -->
-.literal off
-
-
-.vlist
-.vitem &%--%&
-.oindex "--"
-.cindex "options" "command line; terminating"
-This is a pseudo-option whose only purpose is to terminate the options and
-therefore to cause subsequent command line items to be treated as arguments
-rather than options, even if they begin with hyphens.
-
-.vitem &%--help%&
-.oindex "&%--help%&"
-This option causes Exim to output a few sentences stating what it is.
-The same output is generated if the Exim binary is called with no options and
-no arguments.
-
-.vitem &%--version%&
-.oindex "&%--version%&"
-This option is an alias for &%-bV%& and causes version information to be
-displayed.
-
-.vitem &%-Ac%& &&&
-       &%-Am%&
-.oindex "&%-Ac%&"
-.oindex "&%-Am%&"
-These options are used by Sendmail for selecting configuration files and are
-ignored by Exim.
-
-.vitem &%-B%&<&'type'&>
-.oindex "&%-B%&"
-.cindex "8-bit characters"
-.cindex "Sendmail compatibility" "8-bit characters"
-This is a Sendmail option for selecting 7 or 8 bit processing. Exim is 8-bit
-clean; it ignores this option.
-
-.vitem &%-bd%&
-.oindex "&%-bd%&"
-.cindex "daemon"
-.cindex "SMTP" "listener"
-.cindex "queue runner"
-This option runs Exim as a daemon, awaiting incoming SMTP connections. Usually
-the &%-bd%& option is combined with the &%-q%&<&'time'&> option, to specify
-that the daemon should also initiate periodic queue runs.
-
-The &%-bd%& option can be used only by an admin user. If either of the &%-d%&
-(debugging) or &%-v%& (verifying) options are set, the daemon does not
-disconnect from the controlling terminal. When running this way, it can be
-stopped by pressing ctrl-C.
-
-By default, Exim listens for incoming connections to the standard SMTP port on
-all the host's running interfaces. However, it is possible to listen on other
-ports, on multiple ports, and only on specific interfaces. Chapter
-&<<CHAPinterfaces>>& contains a description of the options that control this.
-
-When a listening daemon
-.cindex "daemon" "process id (pid)"
-.cindex "pid (process id)" "of daemon"
-is started without the use of &%-oX%& (that is, without overriding the normal
-configuration), it writes its process id to a file called &_exim-daemon.pid_&
-in Exim's spool directory. This location can be overridden by setting
-PID_FILE_PATH in &_Local/Makefile_&. The file is written while Exim is still
-running as root.
-
-When &%-oX%& is used on the command line to start a listening daemon, the
-process id is not written to the normal pid file path. However, &%-oP%& can be
-used to specify a path on the command line if a pid file is required.
-
-The SIGHUP signal
-.cindex "SIGHUP"
-.cindex restart "on HUP signal"
-.cindex signal "HUP, to restart"
-.cindex "daemon" "restarting"
-.cindex signal "to reload configuration"
-.cindex daemon "reload configuration"
-.cindex reload configuration
-can be used to cause the daemon to re-execute itself. This should be done
-whenever Exim's configuration file, or any file that is incorporated into it by
-means of the &%.include%& facility, is changed, and also whenever a new version
-of Exim is installed. It is not necessary to do this when other files that are
-referenced from the configuration (for example, alias files) are changed,
-because these are reread each time they are used.
-
-.vitem &%-bdf%&
-.oindex "&%-bdf%&"
-This option has the same effect as &%-bd%& except that it never disconnects
-from the controlling terminal, even when no debugging is specified.
-
-.vitem &%-be%&
-.oindex "&%-be%&"
-.cindex "testing" "string expansion"
-.cindex "expansion" "testing"
-Run Exim in expansion testing mode. Exim discards its root privilege, to
-prevent ordinary users from using this mode to read otherwise inaccessible
-files. If no arguments are given, Exim runs interactively, prompting for lines
-of data. Otherwise, it processes each argument in turn.
-
-If Exim was built with USE_READLINE=yes in &_Local/Makefile_&, it tries
-to load the &%libreadline%& library dynamically whenever the &%-be%& option is
-used without command line arguments. If successful, it uses the &[readline()]&
-function, which provides extensive line-editing facilities, for reading the
-test data. A line history is supported.
-
-Long expansion expressions can be split over several lines by using backslash
-continuations. As in Exim's runtime configuration, white space at the start of
-continuation lines is ignored. Each argument or data line is passed through the
-string expansion mechanism, and the result is output. Variable values from the
-configuration file (for example, &$qualify_domain$&) are available, but no
-message-specific values (such as &$message_exim_id$&) are set, because no message
-is being processed (but see &%-bem%& and &%-Mset%&).
-
-&*Note*&: If you use this mechanism to test lookups, and you change the data
-files or databases you are using, you must exit and restart Exim before trying
-the same lookup again. Otherwise, because each Exim process caches the results
-of lookups, you will just get the same result as before.
-
-Macro processing is done on lines before string-expansion: new macros can be
-defined and macros will be expanded.
-Because macros in the config file are often used for secrets, those are only
-available to admin users.
-
-.vitem &%-bem%&&~<&'filename'&>
-.oindex "&%-bem%&"
-.cindex "testing" "string expansion"
-.cindex "expansion" "testing"
-This option operates like &%-be%& except that it must be followed by the name
-of a file. For example:
-.code
-exim -bem /tmp/testmessage
-.endd
-The file is read as a message (as if receiving a locally-submitted non-SMTP
-message) before any of the test expansions are done. Thus, message-specific
-variables such as &$message_size$& and &$header_from:$& are available. However,
-no &'Received:'& header is added to the message. If the &%-t%& option is set,
-recipients are read from the headers in the normal way, and are shown in the
-&$recipients$& variable. Note that recipients cannot be given on the command
-line, because further arguments are taken as strings to expand (just like
-&%-be%&).
-
-.vitem &%-bF%&&~<&'filename'&>
-.oindex "&%-bF%&"
-.cindex "system filter" "testing"
-.cindex "testing" "system filter"
-This option is the same as &%-bf%& except that it assumes that the filter being
-tested is a system filter. The additional commands that are available only in
-system filters are recognized.
-
-.vitem &%-bf%&&~<&'filename'&>
-.oindex "&%-bf%&"
-.cindex "filter" "testing"
-.cindex "testing" "filter file"
-.cindex "forward file" "testing"
-.cindex "testing" "forward file"
-.cindex "Sieve filter" "testing"
-This option runs Exim in user filter testing mode; the file is the filter file
-to be tested, and a test message must be supplied on the standard input. If
-there are no message-dependent tests in the filter, an empty file can be
-supplied.
-
-If you want to test a system filter file, use &%-bF%& instead of &%-bf%&. You
-can use both &%-bF%& and &%-bf%& on the same command, in order to test a system
-filter and a user filter in the same run. For example:
-.code
-exim -bF /system/filter -bf /user/filter </test/message
-.endd
-This is helpful when the system filter adds header lines or sets filter
-variables that are used by the user filter.
-
-If the test filter file does not begin with one of the special lines
-.code
-# Exim filter
-# Sieve filter
-.endd
-it is taken to be a normal &_.forward_& file, and is tested for validity under
-that interpretation. See sections &<<SECTitenonfilred>>& to
-&<<SECTspecitredli>>& for a description of the possible contents of non-filter
-redirection lists.
-
-The result of an Exim command that uses &%-bf%&, provided no errors are
-detected, is a list of the actions that Exim would try to take if presented
-with the message for real. More details of filter testing are given in the
-separate document entitled &'Exim's interfaces to mail filtering'&.
-
-When testing a filter file,
-.cindex "&""From""& line"
-.cindex "envelope from"
-.cindex "envelope sender"
-.oindex "&%-f%&" "for filter testing"
-the envelope sender can be set by the &%-f%& option,
-or by a &"From&~"& line at the start of the test message. Various parameters
-that would normally be taken from the envelope recipient address of the message
-can be set by means of additional command line options (see the next four
-options).
-
-.vitem &%-bfd%&&~<&'domain'&>
-.oindex "&%-bfd%&"
-.vindex "&$qualify_domain$&"
-This sets the domain of the recipient address when a filter file is being
-tested by means of the &%-bf%& option. The default is the value of
-&$qualify_domain$&.
-
-.vitem &%-bfl%&&~<&'local&~part'&>
-.oindex "&%-bfl%&"
-This sets the local part of the recipient address when a filter file is being
-tested by means of the &%-bf%& option. The default is the username of the
-process that calls Exim. A local part should be specified with any prefix or
-suffix stripped, because that is how it appears to the filter when a message is
-actually being delivered.
-
-.vitem &%-bfp%&&~<&'prefix'&>
-.oindex "&%-bfp%&"
-.cindex affix "filter testing"
-This sets the prefix of the local part of the recipient address when a filter
-file is being tested by means of the &%-bf%& option. The default is an empty
-prefix.
-
-.vitem &%-bfs%&&~<&'suffix'&>
-.oindex "&%-bfs%&"
-.cindex affix "filter testing"
-This sets the suffix of the local part of the recipient address when a filter
-file is being tested by means of the &%-bf%& option. The default is an empty
-suffix.
-
-.vitem &%-bh%&&~<&'IP&~address'&>
-.oindex "&%-bh%&"
-.cindex "testing" "incoming SMTP"
-.cindex "SMTP" "testing incoming"
-.cindex "testing" "relay control"
-.cindex "relaying" "testing configuration"
-.cindex "policy control" "testing"
-.cindex "debugging" "&%-bh%& option"
-This option runs a fake SMTP session as if from the given IP address, using the
-standard input and output. The IP address may include a port number at the end,
-after a full stop. For example:
-.code
-exim -bh 10.9.8.7.1234
-exim -bh fe80::a00:20ff:fe86:a061.5678
-.endd
-When an IPv6 address is given, it is converted into canonical form. In the case
-of the second example above, the value of &$sender_host_address$& after
-conversion to the canonical form is
-&`fe80:0000:0000:0a00:20ff:fe86:a061.5678`&.
-
-Comments as to what is going on are written to the standard error file. These
-include lines beginning with &"LOG"& for anything that would have been logged.
-This facility is provided for testing configuration options for incoming
-messages, to make sure they implement the required policy. For example, you can
-test your relay controls using &%-bh%&.
-
-&*Warning 1*&:
-.cindex "RFC 1413"
-You can test features of the configuration that rely on ident (RFC 1413)
-information by using the &%-oMt%& option. However, Exim cannot actually perform
-an ident callout when testing using &%-bh%& because there is no incoming SMTP
-connection.
-
-&*Warning 2*&: Address verification callouts (see section &<<SECTcallver>>&)
-are also skipped when testing using &%-bh%&. If you want these callouts to
-occur, use &%-bhc%& instead.
-
-Messages supplied during the testing session are discarded, and nothing is
-written to any of the real log files. There may be pauses when DNS (and other)
-lookups are taking place, and of course these may time out. The &%-oMi%& option
-can be used to specify a specific IP interface and port if this is important,
-and &%-oMaa%& and &%-oMai%& can be used to set parameters as if the SMTP
-session were authenticated.
-
-The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%& whose
-output just states whether a given recipient address from a given host is
-acceptable or not. See section &<<SECTcheckaccess>>&.
-
-Features such as authentication and encryption, where the client input is not
-plain text, cannot easily be tested with &%-bh%&. Instead, you should use a
-specialized SMTP test program such as
-&url(https://www.jetmore.org/john/code/swaks/,swaks).
-
-.vitem &%-bhc%&&~<&'IP&~address'&>
-.oindex "&%-bhc%&"
-This option operates in the same way as &%-bh%&, except that address
-verification callouts are performed if required. This includes consulting and
-updating the callout cache database.
-
-.vitem &%-bi%&
-.oindex "&%-bi%&"
-.cindex "alias file" "building"
-.cindex "building alias file"
-.cindex "Sendmail compatibility" "&%-bi%& option"
-Sendmail interprets the &%-bi%& option as a request to rebuild its alias file.
-Exim does not have the concept of a single alias file, and so it cannot mimic
-this behaviour. However, calls to &_/usr/lib/sendmail_& with the &%-bi%& option
-tend to appear in various scripts such as NIS make files, so the option must be
-recognized.
-
-If &%-bi%& is encountered, the command specified by the &%bi_command%&
-configuration option is run, under the uid and gid of the caller of Exim. If
-the &%-oA%& option is used, its value is passed to the command as an argument.
-The command set by &%bi_command%& may not contain arguments. The command can
-use the &'exim_dbmbuild'& utility, or some other means, to rebuild alias files
-if this is required. If the &%bi_command%& option is not set, calling Exim with
-&%-bi%& is a no-op.
-
-. // Keep :help first, then the rest in alphabetical order
-.vitem &%-bI:help%&
-.oindex "&%-bI:help%&"
-.cindex "querying exim information"
-We shall provide various options starting &`-bI:`& for querying Exim for
-information.  The output of many of these will be intended for machine
-consumption.  This one is not.  The &%-bI:help%& option asks Exim for a
-synopsis of supported options beginning &`-bI:`&.  Use of any of these
-options shall cause Exim to exit after producing the requested output.
-
-.vitem &%-bI:dscp%&
-.oindex "&%-bI:dscp%&"
-.cindex "DSCP" "values"
-This option causes Exim to emit an alphabetically sorted list of all
-recognised DSCP names.
-
-.vitem &%-bI:sieve%&
-.oindex "&%-bI:sieve%&"
-.cindex "Sieve filter" "capabilities"
-This option causes Exim to emit an alphabetically sorted list of all supported
-Sieve protocol extensions on stdout, one per line.  This is anticipated to be
-useful for ManageSieve (RFC 5804) implementations, in providing that protocol's
-&`SIEVE`& capability response line.  As the precise list may depend upon
-compile-time build options, which this option will adapt to, this is the only
-way to guarantee a correct response.
-
-.vitem &%-bm%&
-.oindex "&%-bm%&"
-.cindex "local message reception"
-This option runs an Exim receiving process that accepts an incoming,
-locally-generated message on the standard input. The recipients are given as the
-command arguments (except when &%-t%& is also present &-- see below). Each
-argument can be a comma-separated list of RFC 2822 addresses. This is the
-default option for selecting the overall action of an Exim call; it is assumed
-if no other conflicting option is present.
-
-If any addresses in the message are unqualified (have no domain), they are
-qualified by the values of the &%qualify_domain%& or &%qualify_recipient%&
-options, as appropriate. The &%-bnq%& option (see below) provides a way of
-suppressing this for special cases.
-
-Policy checks on the contents of local messages can be enforced by means of
-the non-SMTP ACL. See chapter &<<CHAPACL>>& for details.
-
-.cindex "return code" "for &%-bm%&"
-The return code is zero if the message is successfully accepted. Otherwise, the
-action is controlled by the &%-oe%&&'x'& option setting &-- see below.
-
-The format
-.cindex "message" "format"
-.cindex "format" "message"
-.cindex "&""From""& line"
-.cindex "UUCP" "&""From""& line"
-.cindex "Sendmail compatibility" "&""From""& line"
-of the message must be as defined in RFC 2822, except that, for
-compatibility with Sendmail and Smail, a line in one of the forms
-.code
-From sender Fri Jan  5 12:55 GMT 1997
-From sender Fri, 5 Jan 97 12:55:01
-.endd
-(with the weekday optional, and possibly with additional text after the date)
-is permitted to appear at the start of the message. There appears to be no
-authoritative specification of the format of this line. Exim recognizes it by
-matching against the regular expression defined by the &%uucp_from_pattern%&
-option, which can be changed if necessary.
-
-.oindex "&%-f%&" "overriding &""From""& line"
-The specified sender is treated as if it were given as the argument to the
-&%-f%& option, but if a &%-f%& option is also present, its argument is used in
-preference to the address taken from the message. The caller of Exim must be a
-trusted user for the sender of a message to be set in this way.
-
-.vitem &%-bmalware%&&~<&'filename'&>
-.oindex "&%-bmalware%&"
-.cindex "testing", "malware"
-.cindex "malware scan test"
-This debugging option causes Exim to scan the given file or directory
-(depending on the used scanner interface),
-using the malware scanning framework.  The option of &%av_scanner%& influences
-this option, so if &%av_scanner%&'s value is dependent upon an expansion then
-the expansion should have defaults which apply to this invocation.  ACLs are
-not invoked, so if &%av_scanner%& references an ACL variable then that variable
-will never be populated and &%-bmalware%& will fail.
-
-Exim will have changed working directory before resolving the filename, so
-using fully qualified pathnames is advisable.  Exim will be running as the Exim
-user when it tries to open the file, rather than as the invoking user.
-This option requires admin privileges.
-
-The &%-bmalware%& option will not be extended to be more generally useful,
-there are better tools for file-scanning.  This option exists to help
-administrators verify their Exim and AV scanner configuration.
-
-.vitem &%-bnq%&
-.oindex "&%-bnq%&"
-.cindex "address qualification, suppressing"
-By default, Exim automatically qualifies unqualified addresses (those
-without domains) that appear in messages that are submitted locally (that
-is, not over TCP/IP). This qualification applies both to addresses in
-envelopes, and addresses in header lines. Sender addresses are qualified using
-&%qualify_domain%&, and recipient addresses using &%qualify_recipient%& (which
-defaults to the value of &%qualify_domain%&).
-
-Sometimes, qualification is not wanted. For example, if &%-bS%& (batch SMTP) is
-being used to re-submit messages that originally came from remote hosts after
-content scanning, you probably do not want to qualify unqualified addresses in
-header lines. (Such lines will be present only if you have not enabled a header
-syntax check in the appropriate ACL.)
-
-The &%-bnq%& option suppresses all qualification of unqualified addresses in
-messages that originate on the local host. When this is used, unqualified
-addresses in the envelope provoke errors (causing message rejection) and
-unqualified addresses in header lines are left alone.
-
-
-.vitem &%-bP%&
-.oindex "&%-bP%&"
-.cindex "configuration options" "extracting"
-.cindex "options" "configuration &-- extracting"
-If this option is given with no arguments, it causes the values of all Exim's
-main configuration options to be written to the standard output. The values
-of one or more specific options can be requested by giving their names as
-arguments, for example:
-.code
-exim -bP qualify_domain hold_domains
-.endd
-.cindex "hiding configuration option values"
-.cindex "configuration options" "hiding value of"
-.cindex "options" "hiding value of"
-However, any option setting that is preceded by the word &"hide"& in the
-configuration file is not shown in full, except to an admin user. For other
-users, the output is as in this example:
-.code
-mysql_servers = <value not displayable>
-.endd
-If &%config%& is given as an argument, the config is
-output, as it was parsed, any include file resolved, any comment removed.
-
-If &%config_file%& is given as an argument, the name of the runtime
-configuration file is output. (&%configure_file%& works too, for
-backward compatibility.)
-If a list of configuration files was supplied, the value that is output here
-is the name of the file that was actually used.
-
-.cindex "options" "hiding name of"
-If the &%-n%& flag is given, then for most modes of &%-bP%& operation the
-name will not be output.
-
-.cindex "daemon" "process id (pid)"
-.cindex "pid (process id)" "of daemon"
-If &%log_file_path%& or &%pid_file_path%& are given, the names of the
-directories where log files and daemon pid files are written are output,
-respectively. If these values are unset, log files are written in a
-sub-directory of the spool directory called &%log%&, and the pid file is
-written directly into the spool directory.
-
-If &%-bP%& is followed by a name preceded by &`+`&, for example,
-.code
-exim -bP +local_domains
-.endd
-it searches for a matching named list of any type (domain, host, address, or
-local part) and outputs what it finds.
-
-.cindex "options" "router &-- extracting"
-.cindex "options" "transport &-- extracting"
-.cindex "options" "authenticator &-- extracting"
-If one of the words &%router%&, &%transport%&, or &%authenticator%& is given,
-followed by the name of an appropriate driver instance, the option settings for
-that driver are output. For example:
-.code
-exim -bP transport local_delivery
-.endd
-The generic driver options are output first, followed by the driver's private
-options. A list of the names of drivers of a particular type can be obtained by
-using one of the words &%router_list%&, &%transport_list%&, or
-&%authenticator_list%&, and a complete list of all drivers with their option
-settings can be obtained by using &%routers%&, &%transports%&, or
-&%authenticators%&.
-
-.cindex "environment"
-If &%environment%& is given as an argument, the set of environment
-variables is output, line by line. Using the &%-n%& flag suppresses the value of the
-variables.
-
-.cindex "options" "macro &-- extracting"
-If invoked by an admin user, then &%macro%&, &%macro_list%& and &%macros%&
-are available, similarly to the drivers.  Because macros are sometimes used
-for storing passwords, this option is restricted.
-The output format is one item per line.
-For the "-bP macro <name>" form, if no such macro is found
-the exit status will be nonzero.
-
-.vitem &%-bp%&
-.oindex "&%-bp%&"
-.cindex "queue" "listing messages in"
-.cindex "listing" "messages in the queue"
-This option requests a listing of the contents of the mail queue on the
-standard output. If the &%-bp%& option is followed by a list of message ids,
-just those messages are listed. By default, this option can be used only by an
-admin user. However, the &%queue_list_requires_admin%& option can be set false
-to allow any user to see the queue.
-
-Each message in the queue is displayed as in the following example:
-.code
-25m  2.9K 0t5C6f-0000c8-00 <alice@wonderland.fict.example>
-          red.king@looking-glass.fict.example
-          <other addresses>
-.endd
-.cindex "message" "size in queue listing"
-.cindex "size" "of message"
-The first line contains the length of time the message has been in the queue
-(in this case 25 minutes), the size of the message (2.9K), the unique local
-identifier for the message, and the message sender, as contained in the
-envelope. For bounce messages, the sender address is empty, and appears as
-&"<>"&. If the message was submitted locally by an untrusted user who overrode
-the default sender address, the user's login name is shown in parentheses
-before the sender address.
-
-.cindex "frozen messages" "in queue listing"
-If the message is frozen (attempts to deliver it are suspended) then the text
-&"*** frozen ***"& is displayed at the end of this line.
-
-The recipients of the message (taken from the envelope, not the headers) are
-displayed on subsequent lines. Those addresses to which the message has already
-been delivered are marked with the letter D. If an original address gets
-expanded into several addresses via an alias or forward file, the original is
-displayed with a D only when deliveries for all of its child addresses are
-complete.
-
-
-.vitem &%-bpa%&
-.oindex "&%-bpa%&"
-This option operates like &%-bp%&, but in addition it shows delivered addresses
-that were generated from the original top level address(es) in each message by
-alias or forwarding operations. These addresses are flagged with &"+D"& instead
-of just &"D"&.
-
-
-.vitem &%-bpc%&
-.oindex "&%-bpc%&"
-.cindex "queue" "count of messages on"
-This option counts the number of messages in the queue, and writes the total
-to the standard output. It is restricted to admin users, unless
-&%queue_list_requires_admin%& is set false.
-
-
-.vitem &%-bpr%&
-.oindex "&%-bpr%&"
-This option operates like &%-bp%&, but the output is not sorted into
-chronological order of message arrival. This can speed it up when there are
-lots of messages in the queue, and is particularly useful if the output is
-going to be post-processed in a way that doesn't need the sorting.
-
-.vitem &%-bpra%&
-.oindex "&%-bpra%&"
-This option is a combination of &%-bpr%& and &%-bpa%&.
-
-.vitem &%-bpru%&
-.oindex "&%-bpru%&"
-This option is a combination of &%-bpr%& and &%-bpu%&.
-
-
-.vitem &%-bpu%&
-.oindex "&%-bpu%&"
-This option operates like &%-bp%& but shows only undelivered top-level
-addresses for each message displayed. Addresses generated by aliasing or
-forwarding are not shown, unless the message was deferred after processing by a
-router with the &%one_time%& option set.
-
-
-.vitem &%-brt%&
-.oindex "&%-brt%&"
-.cindex "testing" "retry configuration"
-.cindex "retry" "configuration testing"
-This option is for testing retry rules, and it must be followed by up to three
-arguments. It causes Exim to look for a retry rule that matches the values
-and to write it to the standard output. For example:
-.code
-exim -brt bach.comp.mus.example
-Retry rule: *.comp.mus.example  F,2h,15m; F,4d,30m;
-.endd
-See chapter &<<CHAPretry>>& for a description of Exim's retry rules. The first
-argument, which is required, can be a complete address in the form
-&'local_part@domain'&, or it can be just a domain name. If the second argument
-contains a dot, it is interpreted as an optional second domain name; if no
-retry rule is found for the first argument, the second is tried. This ties in
-with Exim's behaviour when looking for retry rules for remote hosts &-- if no
-rule is found that matches the host, one that matches the mail domain is
-sought. Finally, an argument that is the name of a specific delivery error, as
-used in setting up retry rules, can be given. For example:
-.code
-exim -brt haydn.comp.mus.example quota_3d
-Retry rule: *@haydn.comp.mus.example quota_3d  F,1h,15m
-.endd
-
-.vitem &%-brw%&
-.oindex "&%-brw%&"
-.cindex "testing" "rewriting"
-.cindex "rewriting" "testing"
-This option is for testing address rewriting rules, and it must be followed by
-a single argument, consisting of either a local part without a domain, or a
-complete address with a fully qualified domain. Exim outputs how this address
-would be rewritten for each possible place it might appear. See chapter
-&<<CHAPrewrite>>& for further details.
-
-.vitem &%-bS%&
-.oindex "&%-bS%&"
-.cindex "SMTP" "batched incoming"
-.cindex "batched SMTP input"
-This option is used for batched SMTP input, which is an alternative interface
-for non-interactive local message submission. A number of messages can be
-submitted in a single run. However, despite its name, this is not really SMTP
-input. Exim reads each message's envelope from SMTP commands on the standard
-input, but generates no responses. If the caller is trusted, or
-&%untrusted_set_sender%& is set, the senders in the SMTP MAIL commands are
-believed; otherwise the sender is always the caller of Exim.
-
-The message itself is read from the standard input, in SMTP format (leading
-dots doubled), terminated by a line containing just a single dot. An error is
-provoked if the terminating dot is missing. A further message may then follow.
-
-As for other local message submissions, the contents of incoming batch SMTP
-messages can be checked using the non-SMTP ACL (see chapter &<<CHAPACL>>&).
-Unqualified addresses are automatically qualified using &%qualify_domain%& and
-&%qualify_recipient%&, as appropriate, unless the &%-bnq%& option is used.
-
-Some other SMTP commands are recognized in the input. HELO and EHLO act
-as RSET; VRFY, EXPN, ETRN, and HELP act as NOOP;
-QUIT quits, ignoring the rest of the standard input.
-
-.cindex "return code" "for &%-bS%&"
-If any error is encountered, reports are written to the standard output and
-error streams, and Exim gives up immediately. The return code is 0 if no error
-was detected; it is 1 if one or more messages were accepted before the error
-was detected; otherwise it is 2.
-
-More details of input using batched SMTP are given in section
-&<<SECTincomingbatchedSMTP>>&.
-
-.vitem &%-bs%&
-.oindex "&%-bs%&"
-.cindex "SMTP" "local input"
-.cindex "local SMTP input"
-This option causes Exim to accept one or more messages by reading SMTP commands
-on the standard input, and producing SMTP replies on the standard output. SMTP
-policy controls, as defined in ACLs (see chapter &<<CHAPACL>>&) are applied.
-Some user agents use this interface as a way of passing locally-generated
-messages to the MTA.
-
-In
-.cindex "sender" "source of"
-this usage, if the caller of Exim is trusted, or &%untrusted_set_sender%& is
-set, the senders of messages are taken from the SMTP MAIL commands.
-Otherwise the content of these commands is ignored and the sender is set up as
-the calling user. Unqualified addresses are automatically qualified using
-&%qualify_domain%& and &%qualify_recipient%&, as appropriate, unless the
-&%-bnq%& option is used.
-
-.cindex "inetd"
-The
-&%-bs%& option is also used to run Exim from &'inetd'&, as an alternative to
-using a listening daemon. Exim can distinguish the two cases by checking
-whether the standard input is a TCP/IP socket. When Exim is called from
-&'inetd'&, the source of the mail is assumed to be remote, and the comments
-above concerning senders and qualification do not apply. In this situation,
-Exim behaves in exactly the same way as it does when receiving a message via
-the listening daemon.
-
-.vitem &%-bt%&
-.oindex "&%-bt%&"
-.cindex "testing" "addresses"
-.cindex "address" "testing"
-This option runs Exim in address testing mode, in which each argument is taken
-as a recipient address to be tested for deliverability. The results are
-written to the standard output. If a test fails, and the caller is not an admin
-user, no details of the failure are output, because these might contain
-sensitive information such as usernames and passwords for database lookups.
-
-If no arguments are given, Exim runs in an interactive manner, prompting with a
-right angle bracket for addresses to be tested.
-
-Unlike the &%-be%& test option, you cannot arrange for Exim to use the
-&[readline()]& function, because it is running as &'root'& and there are
-security issues.
-
-Each address is handled as if it were the recipient address of a message
-(compare the &%-bv%& option). It is passed to the routers and the result is
-written to the standard output. However, any router that has
-&%no_address_test%& set is bypassed. This can make &%-bt%& easier to use for
-genuine routing tests if your first router passes everything to a scanner
-program.
-
-.cindex "return code" "for &%-bt%&"
-The return code is 2 if any address failed outright; it is 1 if no address
-failed outright but at least one could not be resolved for some reason. Return
-code 0 is given only when all addresses succeed.
-
-.cindex "duplicate addresses"
-&*Note*&: When actually delivering a message, Exim removes duplicate recipient
-addresses after routing is complete, so that only one delivery takes place.
-This does not happen when testing with &%-bt%&; the full results of routing are
-always shown.
-
-&*Warning*&: &%-bt%& can only do relatively simple testing. If any of the
-routers in the configuration makes any tests on the sender address of a
-message,
-.oindex "&%-f%&" "for address testing"
-you can use the &%-f%& option to set an appropriate sender when running
-&%-bt%& tests. Without it, the sender is assumed to be the calling user at the
-default qualifying domain. However, if you have set up (for example) routers
-whose behaviour depends on the contents of an incoming message, you cannot test
-those conditions using &%-bt%&. The &%-N%& option provides a possible way of
-doing such tests.
-
-.vitem &%-bV%&
-.oindex "&%-bV%&"
-.cindex "version number of Exim"
-This option causes Exim to write the current version number, compilation
-number, and compilation date of the &'exim'& binary to the standard output.
-It also lists the DBM library that is being used, the optional modules (such as
-specific lookup types), the drivers that are included in the binary, and the
-name of the runtime configuration file that is in use.
-
-As part of its operation, &%-bV%& causes Exim to read and syntax check its
-configuration file. However, this is a static check only. It cannot check
-values that are to be expanded. For example, although a misspelt ACL verb is
-detected, an error in the verb's arguments is not. You cannot rely on &%-bV%&
-alone to discover (for example) all the typos in the configuration; some
-realistic testing is needed. The &%-bh%& and &%-N%& options provide more
-dynamic testing facilities.
-
-.vitem &%-bv%&
-.oindex "&%-bv%&"
-.cindex "verifying address" "using &%-bv%&"
-.cindex "address" "verification"
-This option runs Exim in address verification mode, in which each argument is
-taken as a recipient address to be verified by the routers. (This does
-not involve any verification callouts). During normal operation, verification
-happens mostly as a consequence processing a &%verify%& condition in an ACL
-(see chapter &<<CHAPACL>>&). If you want to test an entire ACL, possibly
-including callouts, see the &%-bh%& and &%-bhc%& options.
-
-If verification fails, and the caller is not an admin user, no details of the
-failure are output, because these might contain sensitive information such as
-usernames and passwords for database lookups.
-
-If no arguments are given, Exim runs in an interactive manner, prompting with a
-right angle bracket for addresses to be verified.
-
-Unlike the &%-be%& test option, you cannot arrange for Exim to use the
-&[readline()]& function, because it is running as &'exim'& and there are
-security issues.
-
-Verification differs from address testing (the &%-bt%& option) in that routers
-that have &%no_verify%& set are skipped, and if the address is accepted by a
-router that has &%fail_verify%& set, verification fails. The address is
-verified as a recipient if &%-bv%& is used; to test verification for a sender
-address, &%-bvs%& should be used.
-
-If the &%-v%& option is not set, the output consists of a single line for each
-address, stating whether it was verified or not, and giving a reason in the
-latter case. Without &%-v%&, generating more than one address by redirection
-causes verification to end successfully, without considering the generated
-addresses. However, if just one address is generated, processing continues,
-and the generated address must verify successfully for the overall verification
-to succeed.
-
-When &%-v%& is set, more details are given of how the address has been handled,
-and in the case of address redirection, all the generated addresses are also
-considered. Verification may succeed for some and fail for others.
-
-The
-.cindex "return code" "for &%-bv%&"
-return code is 2 if any address failed outright; it is 1 if no address
-failed outright but at least one could not be resolved for some reason. Return
-code 0 is given only when all addresses succeed.
-
-If any of the routers in the configuration makes any tests on the sender
-address of a message, you should use the &%-f%& option to set an appropriate
-sender when running &%-bv%& tests. Without it, the sender is assumed to be the
-calling user at the default qualifying domain.
-
-.vitem &%-bvs%&
-.oindex "&%-bvs%&"
-This option acts like &%-bv%&, but verifies the address as a sender rather
-than a recipient address. This affects any rewriting and qualification that
-might happen.
-
-.vitem &%-bw%&
-.oindex "&%-bw%&"
-.cindex "daemon"
-.cindex "inetd"
-.cindex "inetd" "wait mode"
-This option runs Exim as a daemon, awaiting incoming SMTP connections,
-similarly to the &%-bd%& option.  All port specifications on the command-line
-and in the configuration file are ignored.  Queue-running may not be specified.
-
-In this mode, Exim expects to be passed a socket as fd 0 (stdin) which is
-listening for connections.  This permits the system to start up and have
-inetd (or equivalent) listen on the SMTP ports, starting an Exim daemon for
-each port only when the first connection is received.
-
-If the option is given as &%-bw%&<&'time'&> then the time is a timeout, after
-which the daemon will exit, which should cause inetd to listen once more.
-
-.vitem &%-C%&&~<&'filelist'&>
-.oindex "&%-C%&"
-.cindex "configuration file" "alternate"
-.cindex "CONFIGURE_FILE"
-.cindex "alternate configuration file"
-This option causes Exim to find the runtime configuration file from the given
-list instead of from the list specified by the CONFIGURE_FILE
-compile-time setting. Usually, the list will consist of just a single filename,
-but it can be a colon-separated list of names. In this case, the first
-file that exists is used. Failure to open an existing file stops Exim from
-proceeding any further along the list, and an error is generated.
-
-When this option is used by a caller other than root, and the list is different
-from the compiled-in list, Exim gives up its root privilege immediately, and
-runs with the real and effective uid and gid set to those of the caller.
-However, if a TRUSTED_CONFIG_LIST file is defined in &_Local/Makefile_&, that
-file contains a list of full pathnames, one per line, for configuration files
-which are trusted. Root privilege is retained for any configuration file so
-listed, as long as the caller is the Exim user (or the user specified in the
-CONFIGURE_OWNER option, if any), and as long as the configuration file is
-not writeable by inappropriate users or groups.
-
-Leaving TRUSTED_CONFIG_LIST unset precludes the possibility of testing a
-configuration using &%-C%& right through message reception and delivery,
-even if the caller is root. The reception works, but by that time, Exim is
-running as the Exim user, so when it re-executes to regain privilege for the
-delivery, the use of &%-C%& causes privilege to be lost. However, root can
-test reception and delivery using two separate commands (one to put a message
-in the queue, using &%-odq%&, and another to do the delivery, using &%-M%&).
-
-If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
-prefix string with which any file named in a &%-C%& command line option
-must start. In addition, the filename must not contain the sequence &`/../`&.
-However, if the value of the &%-C%& option is identical to the value of
-CONFIGURE_FILE in &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as
-usual. There is no default setting for ALT_CONFIG_PREFIX; when it is
-unset, any filename can be used with &%-C%&.
-
-ALT_CONFIG_PREFIX can be used to confine alternative configuration files
-to a directory to which only root has access. This prevents someone who has
-broken into the Exim account from running a privileged Exim with an arbitrary
-configuration file.
-
-The &%-C%& facility is useful for ensuring that configuration files are
-syntactically correct, but cannot be used for test deliveries, unless the
-caller is privileged, or unless it is an exotic configuration that does not
-require privilege. No check is made on the owner or group of the files
-specified by this option.
-
-
-.vitem &%-D%&<&'macro'&>=<&'value'&>
-.oindex "&%-D%&"
-.cindex "macro" "setting on command line"
-This option can be used to override macro definitions in the configuration file
-(see section &<<SECTmacrodefs>>&). However, like &%-C%&, if it is used by an
-unprivileged caller, it causes Exim to give up its root privilege.
-If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
-completely disabled, and its use causes an immediate error exit.
-
-If WHITELIST_D_MACROS is defined in &_Local/Makefile_& then it should be a
-colon-separated list of macros which are considered safe and, if &%-D%& only
-supplies macros from this list, and the values are acceptable, then Exim will
-not give up root privilege if the caller is root, the Exim run-time user, or
-the CONFIGURE_OWNER, if set.  This is a transition mechanism and is expected
-to be removed in the future.  Acceptable values for the macros satisfy the
-regexp: &`^[A-Za-z0-9_/.-]*$`&
-
-The entire option (including equals sign if present) must all be within one
-command line item. &%-D%& can be used to set the value of a macro to the empty
-string, in which case the equals sign is optional. These two commands are
-synonymous:
-.code
-exim -DABC  ...
-exim -DABC= ...
-.endd
-To include spaces in a macro definition item, quotes must be used. If you use
-quotes, spaces are permitted around the macro name and the equals sign. For
-example:
-.code
-exim '-D ABC = something' ...
-.endd
-&%-D%& may be repeated up to 10 times on a command line.
-Only macro names up to 22 letters long can be set.
-
-
-.vitem &%-d%&<&'debug&~options'&>
-.oindex "&%-d%&"
-.cindex "debugging" "list of selectors"
-.cindex "debugging" "&%-d%& option"
-This option causes debugging information to be written to the standard
-error stream. It is restricted to admin users because debugging output may show
-database queries that contain password information. Also, the details of users'
-filter files should be protected. If a non-admin user uses &%-d%&, Exim
-writes an error message to the standard error stream and exits with a non-zero
-return code.
-
-When &%-d%& is used, &%-v%& is assumed. If &%-d%& is given on its own, a lot of
-standard debugging data is output. This can be reduced, or increased to include
-some more rarely needed information, by directly following &%-d%& with a string
-made up of names preceded by plus or minus characters. These add or remove sets
-of debugging data, respectively. For example, &%-d+filter%& adds filter
-debugging, whereas &%-d-all+filter%& selects only filter debugging. Note that
-no spaces are allowed in the debug setting. The available debugging categories
-are:
-.display
-&`acl            `& ACL interpretation
-&`auth           `& authenticators
-&`deliver        `& general delivery logic
-&`dns            `& DNS lookups (see also resolver)
-&`dnsbl          `& DNS black list (aka RBL) code
-&`exec           `& arguments for &[execv()]& calls
-&`expand         `& detailed debugging for string expansions
-&`filter         `& filter handling
-&`hints_lookup   `& hints data lookups
-&`host_lookup    `& all types of name-to-IP address handling
-&`ident          `& ident lookup
-&`interface      `& lists of local interfaces
-&`lists          `& matching things in lists
-&`load           `& system load checks
-&`local_scan     `& can be used by &[local_scan()]& (see chapter &&&
-                    &<<CHAPlocalscan>>&)
-&`lookup         `& general lookup code and all lookups
-&`memory         `& memory handling
-&`noutf8         `& modifier: avoid UTF-8 line-drawing
-&`pid            `& modifier: add pid to debug output lines
-&`process_info   `& setting info for the process log
-&`queue_run      `& queue runs
-&`receive        `& general message reception logic
-&`resolver       `& turn on the DNS resolver's debugging output
-&`retry          `& retry handling
-&`rewrite        `& address rewriting
-&`route          `& address routing
-&`timestamp      `& modifier: add timestamp to debug output lines
-&`tls            `& TLS logic
-&`transport      `& transports
-&`uid            `& changes of uid/gid and looking up uid/gid
-&`verify         `& address verification logic
-&`all            `& almost all of the above (see below), and also &%-v%&
-.endd
-The &`all`& option excludes &`memory`& when used as &`+all`&, but includes it
-for &`-all`&. The reason for this is that &`+all`& is something that people
-tend to use when generating debug output for Exim maintainers. If &`+memory`&
-is included, an awful lot of output that is very rarely of interest is
-generated, so it now has to be explicitly requested. However, &`-all`& does
-turn everything off.
-
-.cindex "resolver, debugging output"
-.cindex "DNS resolver, debugging output"
-The &`resolver`& option produces output only if the DNS resolver was compiled
-with DEBUG enabled. This is not the case in some operating systems. Also,
-unfortunately, debugging output from the DNS resolver is written to stdout
-rather than stderr.
-
-The default (&%-d%& with no argument) omits &`expand`&, &`filter`&,
-&`interface`&, &`load`&, &`memory`&, &`pid`&, &`resolver`&, and &`timestamp`&.
-However, the &`pid`& selector is forced when debugging is turned on for a
-daemon, which then passes it on to any re-executed Exims. Exim also
-automatically adds the pid to debug lines when several remote deliveries are
-run in parallel.
-
-The &`timestamp`& selector causes the current time to be inserted at the start
-of all debug output lines. This can be useful when trying to track down delays
-in processing.
-
-.cindex debugging "UTF-8 in"
-.cindex UTF-8 "in debug output"
-The &`noutf8`& selector disables the use of
-UTF-8 line-drawing characters to group related information.
-When disabled. ascii-art is used instead.
-Using the &`+all`& option does not set this modifier,
-
-If the &%debug_print%& option is set in any driver, it produces output whenever
-any debugging is selected, or if &%-v%& is used.
-
-.vitem &%-dd%&<&'debug&~options'&>
-.oindex "&%-dd%&"
-This option behaves exactly like &%-d%& except when used on a command that
-starts a daemon process. In that case, debugging is turned off for the
-subprocesses that the daemon creates. Thus, it is useful for monitoring the
-behaviour of the daemon without creating as much output as full debugging does.
-
-.vitem &%-dropcr%&
-.oindex "&%-dropcr%&"
-This is an obsolete option that is now a no-op. It used to affect the way Exim
-handled CR and LF characters in incoming messages. What happens now is
-described in section &<<SECTlineendings>>&.
-
-.vitem &%-E%&
-.oindex "&%-E%&"
-.cindex "bounce message" "generating"
-This option specifies that an incoming message is a locally-generated delivery
-failure report. It is used internally by Exim when handling delivery failures
-and is not intended for external use. Its only effect is to stop Exim
-generating certain messages to the postmaster, as otherwise message cascades
-could occur in some situations. As part of the same option, a message id may
-follow the characters &%-E%&. If it does, the log entry for the receipt of the
-new message contains the id, following &"R="&, as a cross-reference.
-
-.vitem &%-e%&&'x'&
-.oindex "&%-e%&&'x'&"
-There are a number of Sendmail options starting with &%-oe%& which seem to be
-called by various programs without the leading &%o%& in the option. For
-example, the &%vacation%& program uses &%-eq%&. Exim treats all options of the
-form &%-e%&&'x'& as synonymous with the corresponding &%-oe%&&'x'& options.
-
-.vitem &%-F%&&~<&'string'&>
-.oindex "&%-F%&"
-.cindex "sender" "name"
-.cindex "name" "of sender"
-This option sets the sender's full name for use when a locally-generated
-message is being accepted. In the absence of this option, the user's &'gecos'&
-entry from the password data is used. As users are generally permitted to alter
-their &'gecos'& entries, no security considerations are involved. White space
-between &%-F%& and the <&'string'&> is optional.
-
-.vitem &%-f%&&~<&'address'&>
-.oindex "&%-f%&"
-.cindex "sender" "address"
-.cindex "address" "sender"
-.cindex "trusted users"
-.cindex "envelope from"
-.cindex "envelope sender"
-.cindex "user" "trusted"
-This option sets the address of the envelope sender of a locally-generated
-message (also known as the return path). The option can normally be used only
-by a trusted user, but &%untrusted_set_sender%& can be set to allow untrusted
-users to use it.
-
-Processes running as root or the Exim user are always trusted. Other
-trusted users are defined by the &%trusted_users%& or &%trusted_groups%&
-options. In the absence of &%-f%&, or if the caller is not trusted, the sender
-of a local message is set to the caller's login name at the default qualify
-domain.
-
-There is one exception to the restriction on the use of &%-f%&: an empty sender
-can be specified by any user, trusted or not, to create a message that can
-never provoke a bounce. An empty sender can be specified either as an empty
-string, or as a pair of angle brackets with nothing between them, as in these
-examples of shell commands:
-.code
-exim -f '<>' user@domain
-exim -f "" user@domain
-.endd
-In addition, the use of &%-f%& is not restricted when testing a filter file
-with &%-bf%& or when testing or verifying addresses using the &%-bt%& or
-&%-bv%& options.
-
-Allowing untrusted users to change the sender address does not of itself make
-it possible to send anonymous mail. Exim still checks that the &'From:'& header
-refers to the local user, and if it does not, it adds a &'Sender:'& header,
-though this can be overridden by setting &%no_local_from_check%&.
-
-White
-.cindex "&""From""& line"
-space between &%-f%& and the <&'address'&> is optional (that is, they can be
-given as two arguments or one combined argument). The sender of a
-locally-generated message can also be set (when permitted) by an initial
-&"From&~"& line in the message &-- see the description of &%-bm%& above &-- but
-if &%-f%& is also present, it overrides &"From&~"&.
-
-.vitem &%-G%&
-.oindex "&%-G%&"
-.cindex "submission fixups, suppressing (command-line)"
-This option is equivalent to an ACL applying:
-.code
-control = suppress_local_fixups
-.endd
-for every message received.  Note that Sendmail will complain about such
-bad formatting, where Exim silently just does not fix it up.  This may change
-in future.
-
-As this affects audit information, the caller must be a trusted user to use
-this option.
-
-.vitem &%-h%&&~<&'number'&>
-.oindex "&%-h%&"
-.cindex "Sendmail compatibility" "&%-h%& option ignored"
-This option is accepted for compatibility with Sendmail, but has no effect. (In
-Sendmail it overrides the &"hop count"& obtained by counting &'Received:'&
-headers.)
-
-.vitem &%-i%&
-.oindex "&%-i%&"
-.cindex "Solaris" "&'mail'& command"
-.cindex "dot" "in incoming non-SMTP message"
-This option, which has the same effect as &%-oi%&, specifies that a dot on a
-line by itself should not terminate an incoming, non-SMTP message. I can find
-no documentation for this option in Solaris 2.4 Sendmail, but the &'mailx'&
-command in Solaris 2.4 uses it. See also &%-ti%&.
-
-.vitem &%-L%&&~<&'tag'&>
-.oindex "&%-L%&"
-.cindex "syslog" "process name; set with flag"
-This option is equivalent to setting &%syslog_processname%& in the config
-file and setting &%log_file_path%& to &`syslog`&.
-Its use is restricted to administrators.  The configuration file has to be
-read and parsed, to determine access rights, before this is set and takes
-effect, so early configuration file errors will not honour this flag.
-
-The tag should not be longer than 32 characters.
-
-.vitem &%-M%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
-.oindex "&%-M%&"
-.cindex "forcing delivery"
-.cindex "delivery" "forcing attempt"
-.cindex "frozen messages" "forcing delivery"
-This option requests Exim to run a delivery attempt on each message in turn. If
-any of the messages are frozen, they are automatically thawed before the
-delivery attempt. The settings of &%queue_domains%&, &%queue_smtp_domains%&,
-and &%hold_domains%& are ignored.
-
-Retry
-.cindex "hints database" "overriding retry hints"
-hints for any of the addresses are overridden &-- Exim tries to deliver even if
-the normal retry time has not yet been reached. This option requires the caller
-to be an admin user. However, there is an option called &%prod_requires_admin%&
-which can be set false to relax this restriction (and also the same requirement
-for the &%-q%&, &%-R%&, and &%-S%& options).
-
-The deliveries happen synchronously, that is, the original Exim process does
-not terminate until all the delivery attempts have finished. No output is
-produced unless there is a serious error. If you want to see what is happening,
-use the &%-v%& option as well, or inspect Exim's main log.
-
-.vitem &%-Mar%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
-.oindex "&%-Mar%&"
-.cindex "message" "adding recipients"
-.cindex "recipient" "adding"
-This option requests Exim to add the addresses to the list of recipients of the
-message (&"ar"& for &"add recipients"&). The first argument must be a message
-id, and the remaining ones must be email addresses. However, if the message is
-active (in the middle of a delivery attempt), it is not altered. This option
-can be used only by an admin user.
-
-.vitem "&%-MC%&&~<&'transport'&>&~<&'hostname'&>&~<&'sequence&~number'&>&&&
-        &~<&'message&~id'&>"
-.oindex "&%-MC%&"
-.cindex "SMTP" "passed connection"
-.cindex "SMTP" "multiple deliveries"
-.cindex "multiple SMTP deliveries"
-This option is not intended for use by external callers. It is used internally
-by Exim to invoke another instance of itself to deliver a waiting message using
-an existing SMTP connection, which is passed as the standard input. Details are
-given in chapter &<<CHAPSMTP>>&. This must be the final option, and the caller
-must be root or the Exim user in order to use it.
-
-.vitem &%-MCA%&
-.oindex "&%-MCA%&"
-This option is not intended for use by external callers. It is used internally
-by Exim in conjunction with the &%-MC%& option. It signifies that the
-connection to the remote host has been authenticated.
-
-.vitem &%-MCD%&
-.oindex "&%-MCD%&"
-This option is not intended for use by external callers. It is used internally
-by Exim in conjunction with the &%-MC%& option. It signifies that the
-remote host supports the ESMTP &_DSN_& extension.
-
-.new
-.vitem &%-MCd%&
-.oindex "&%-MCd%&"
-This option is not intended for use by external callers. It is used internally
-by Exim in conjunction with the &%-d%& option
-to pass on an information string on the purpose of the process.
-.wen
-
-.vitem &%-MCG%&&~<&'queue&~name'&>
-.oindex "&%-MCG%&"
-This option is not intended for use by external callers. It is used internally
-by Exim in conjunction with the &%-MC%& option. It signifies that an
-alternate queue is used, named by the following argument.
-
-.vitem &%-MCK%&
-.oindex "&%-MCK%&"
-This option is not intended for use by external callers. It is used internally
-by Exim in conjunction with the &%-MC%& option. It signifies that a
-remote host supports the ESMTP &_CHUNKING_& extension.
-
-.vitem &%-MCP%&
-.oindex "&%-MCP%&"
-This option is not intended for use by external callers. It is used internally
-by Exim in conjunction with the &%-MC%& option. It signifies that the server to
-which Exim is connected supports pipelining.
-
-.vitem &%-MCQ%&&~<&'process&~id'&>&~<&'pipe&~fd'&>
-.oindex "&%-MCQ%&"
-This option is not intended for use by external callers. It is used internally
-by Exim in conjunction with the &%-MC%& option when the original delivery was
-started by a queue runner. It passes on the process id of the queue runner,
-together with the file descriptor number of an open pipe. Closure of the pipe
-signals the final completion of the sequence of processes that are passing
-messages through the same SMTP connection.
-
-.vitem &%-MCS%&
-.oindex "&%-MCS%&"
-This option is not intended for use by external callers. It is used internally
-by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
-SMTP SIZE option should be used on messages delivered down the existing
-connection.
-
-.vitem &%-MCT%&
-.oindex "&%-MCT%&"
-This option is not intended for use by external callers. It is used internally
-by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
-host to which Exim is connected supports TLS encryption.
-
-.vitem &%-MCt%&&~<&'IP&~address'&>&~<&'port'&>&~<&'cipher'&>
-.oindex "&%-MCt%&"
-This option is not intended for use by external callers. It is used internally
-by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
-connection is being proxied by a parent process for handling TLS encryption.
-The arguments give the local address and port being proxied, and the TLS cipher.
-
-.vitem &%-Mc%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
-.oindex "&%-Mc%&"
-.cindex "hints database" "not overridden by &%-Mc%&"
-.cindex "delivery" "manually started &-- not forced"
-This option requests Exim to run a delivery attempt on each message, in turn,
-but unlike the &%-M%& option, it does check for retry hints, and respects any
-that are found. This option is not very useful to external callers. It is
-provided mainly for internal use by Exim when it needs to re-invoke itself in
-order to regain root privilege for a delivery (see chapter &<<CHAPsecurity>>&).
-However, &%-Mc%& can be useful when testing, in order to run a delivery that
-respects retry times and other options such as &%hold_domains%& that are
-overridden when &%-M%& is used. Such a delivery does not count as a queue run.
-If you want to run a specific delivery as if in a queue run, you should use
-&%-q%& with a message id argument. A distinction between queue run deliveries
-and other deliveries is made in one or two places.
-
-.vitem &%-Mes%&&~<&'message&~id'&>&~<&'address'&>
-.oindex "&%-Mes%&"
-.cindex "message" "changing sender"
-.cindex "sender" "changing"
-This option requests Exim to change the sender address in the message to the
-given address, which must be a fully qualified address or &"<>"& (&"es"& for
-&"edit sender"&). There must be exactly two arguments. The first argument must
-be a message id, and the second one an email address. However, if the message
-is active (in the middle of a delivery attempt), its status is not altered.
-This option can be used only by an admin user.
-
-.vitem &%-Mf%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
-.oindex "&%-Mf%&"
-.cindex "freezing messages"
-.cindex "message" "manually freezing"
-This option requests Exim to mark each listed message as &"frozen"&. This
-prevents any delivery attempts taking place until the message is &"thawed"&,
-either manually or as a result of the &%auto_thaw%& configuration option.
-However, if any of the messages are active (in the middle of a delivery
-attempt), their status is not altered. This option can be used only by an admin
-user.
-
-.vitem &%-Mg%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
-.oindex "&%-Mg%&"
-.cindex "giving up on messages"
-.cindex "message" "abandoning delivery attempts"
-.cindex "delivery" "abandoning further attempts"
-This option requests Exim to give up trying to deliver the listed messages,
-including any that are frozen. However, if any of the messages are active,
-their status is not altered. For non-bounce messages, a delivery error message
-is sent to the sender, containing the text &"cancelled by administrator"&.
-Bounce messages are just discarded. This option can be used only by an admin
-user.
-
-.vitem &%-MG%&&~<&'queue&~name'&>&~<&'message&~id'&>&~<&'message&~id'&>&~...
-.oindex "&%-MG%&"
-.cindex queue named
-.cindex "named queues" "moving messages"
-.cindex "queue" "moving messages"
-This option requests that each listed message be moved from its current
-queue to the given named queue.
-The destination queue name argument is required, but can be an empty
-string to define the default queue.
-If the messages are not currently located in the default queue,
-a &%-qG<name>%& option will be required to define the source queue.
-
-.vitem &%-Mmad%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
-.oindex "&%-Mmad%&"
-.cindex "delivery" "cancelling all"
-This option requests Exim to mark all the recipient addresses in the messages
-as already delivered (&"mad"& for &"mark all delivered"&). However, if any
-message is active (in the middle of a delivery attempt), its status is not
-altered. This option can be used only by an admin user.
-
-.vitem &%-Mmd%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
-.oindex "&%-Mmd%&"
-.cindex "delivery" "cancelling by address"
-.cindex "recipient" "removing"
-.cindex "removing recipients"
-This option requests Exim to mark the given addresses as already delivered
-(&"md"& for &"mark delivered"&). The first argument must be a message id, and
-the remaining ones must be email addresses. These are matched to recipient
-addresses in the message in a case-sensitive manner. If the message is active
-(in the middle of a delivery attempt), its status is not altered. This option
-can be used only by an admin user.
-
-.vitem &%-Mrm%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
-.oindex "&%-Mrm%&"
-.cindex "removing messages"
-.cindex "abandoning mail"
-.cindex "message" "manually discarding"
-This option requests Exim to remove the given messages from the queue. No
-bounce messages are sent; each message is simply forgotten. However, if any of
-the messages are active, their status is not altered. This option can be used
-only by an admin user or by the user who originally caused the message to be
-placed in the queue.
-
-. .new
-. .vitem &%-MS%&
-. .oindex "&%-MS%&"
-. .cindex REQUIRETLS
-. This option is used to request REQUIRETLS processing on the message.
-. It is used internally by Exim in conjunction with -E when generating
-. a bounce message.
-. .wen
-
-.vitem &%-Mset%&&~<&'message&~id'&>
-.oindex "&%-Mset%&"
-.cindex "testing" "string expansion"
-.cindex "expansion" "testing"
-This option is useful only in conjunction with &%-be%& (that is, when testing
-string expansions). Exim loads the given message from its spool before doing
-the test expansions, thus setting message-specific variables such as
-&$message_size$& and the header variables. The &$recipients$& variable is made
-available. This feature is provided to make it easier to test expansions that
-make use of these variables. However, this option can be used only by an admin
-user. See also &%-bem%&.
-
-.vitem &%-Mt%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
-.oindex "&%-Mt%&"
-.cindex "thawing messages"
-.cindex "unfreezing messages"
-.cindex "frozen messages" "thawing"
-.cindex "message" "thawing frozen"
-This option requests Exim to &"thaw"& any of the listed messages that are
-&"frozen"&, so that delivery attempts can resume. However, if any of the
-messages are active, their status is not altered. This option can be used only
-by an admin user.
-
-.vitem &%-Mvb%&&~<&'message&~id'&>
-.oindex "&%-Mvb%&"
-.cindex "listing" "message body"
-.cindex "message" "listing body of"
-This option causes the contents of the message body (-D) spool file to be
-written to the standard output. This option can be used only by an admin user.
-
-.vitem &%-Mvc%&&~<&'message&~id'&>
-.oindex "&%-Mvc%&"
-.cindex "message" "listing in RFC 2822 format"
-.cindex "listing" "message in RFC 2822 format"
-This option causes a copy of the complete message (header lines plus body) to
-be written to the standard output in RFC 2822 format. This option can be used
-only by an admin user.
-
-.vitem &%-Mvh%&&~<&'message&~id'&>
-.oindex "&%-Mvh%&"
-.cindex "listing" "message headers"
-.cindex "header lines" "listing"
-.cindex "message" "listing header lines"
-This option causes the contents of the message headers (-H) spool file to be
-written to the standard output. This option can be used only by an admin user.
-
-.vitem &%-Mvl%&&~<&'message&~id'&>
-.oindex "&%-Mvl%&"
-.cindex "listing" "message log"
-.cindex "message" "listing message log"
-This option causes the contents of the message log spool file to be written to
-the standard output. This option can be used only by an admin user.
-
-.vitem &%-m%&
-.oindex "&%-m%&"
-This is apparently a synonym for &%-om%& that is accepted by Sendmail, so Exim
-treats it that way too.
-
-.vitem &%-N%&
-.oindex "&%-N%&"
-.cindex "debugging" "&%-N%& option"
-.cindex "debugging" "suppressing delivery"
-This is a debugging option that inhibits delivery of a message at the transport
-level. It implies &%-v%&. Exim goes through many of the motions of delivery &--
-it just doesn't actually transport the message, but instead behaves as if it
-had successfully done so. However, it does not make any updates to the retry
-database, and the log entries for deliveries are flagged with &"*>"& rather
-than &"=>"&.
-
-Because &%-N%& discards any message to which it applies, only root or the Exim
-user are allowed to use it with &%-bd%&, &%-q%&, &%-R%& or &%-M%&. In other
-words, an ordinary user can use it only when supplying an incoming message to
-which it will apply. Although transportation never fails when &%-N%& is set, an
-address may be deferred because of a configuration problem on a transport, or a
-routing problem. Once &%-N%& has been used for a delivery attempt, it sticks to
-the message, and applies to any subsequent delivery attempts that may happen
-for that message.
-
-.vitem &%-n%&
-.oindex "&%-n%&"
-This option is interpreted by Sendmail to mean &"no aliasing"&.
-For normal modes of operation, it is ignored by Exim.
-When combined with &%-bP%& it makes the output more terse (suppresses
-option names, environment values and config pretty printing).
-
-.vitem &%-O%&&~<&'data'&>
-.oindex "&%-O%&"
-This option is interpreted by Sendmail to mean &`set option`&. It is ignored by
-Exim.
-
-.vitem &%-oA%&&~<&'file&~name'&>
-.oindex "&%-oA%&"
-.cindex "Sendmail compatibility" "&%-oA%& option"
-This option is used by Sendmail in conjunction with &%-bi%& to specify an
-alternative alias filename. Exim handles &%-bi%& differently; see the
-description above.
-
-.vitem &%-oB%&&~<&'n'&>
-.oindex "&%-oB%&"
-.cindex "SMTP" "passed connection"
-.cindex "SMTP" "multiple deliveries"
-.cindex "multiple SMTP deliveries"
-This is a debugging option which limits the maximum number of messages that can
-be delivered down one SMTP connection, overriding the value set in any &(smtp)&
-transport. If <&'n'&> is omitted, the limit is set to 1.
-
-.vitem &%-odb%&
-.oindex "&%-odb%&"
-.cindex "background delivery"
-.cindex "delivery" "in the background"
-This option applies to all modes in which Exim accepts incoming messages,
-including the listening daemon. It requests &"background"& delivery of such
-messages, which means that the accepting process automatically starts a
-delivery process for each message received, but does not wait for the delivery
-processes to finish.
-
-When all the messages have been received, the reception process exits,
-leaving the delivery processes to finish in their own time. The standard output
-and error streams are closed at the start of each delivery process.
-This is the default action if none of the &%-od%& options are present.
-
-If one of the queueing options in the configuration file
-(&%queue_only%& or &%queue_only_file%&, for example) is in effect, &%-odb%&
-overrides it if &%queue_only_override%& is set true, which is the default
-setting. If &%queue_only_override%& is set false, &%-odb%& has no effect.
-
-.vitem &%-odf%&
-.oindex "&%-odf%&"
-.cindex "foreground delivery"
-.cindex "delivery" "in the foreground"
-This option requests &"foreground"& (synchronous) delivery when Exim has
-accepted a locally-generated message. (For the daemon it is exactly the same as
-&%-odb%&.) A delivery process is automatically started to deliver the message,
-and Exim waits for it to complete before proceeding.
-
-The original Exim reception process does not finish until the delivery
-process for the final message has ended. The standard error stream is left open
-during deliveries.
-
-However, like &%-odb%&, this option has no effect if &%queue_only_override%& is
-false and one of the queueing options in the configuration file is in effect.
-
-If there is a temporary delivery error during foreground delivery, the
-message is left in the queue for later delivery, and the original reception
-process exits. See chapter &<<CHAPnonqueueing>>& for a way of setting up a
-restricted configuration that never queues messages.
-
-
-.vitem &%-odi%&
-.oindex "&%-odi%&"
-This option is synonymous with &%-odf%&. It is provided for compatibility with
-Sendmail.
-
-.vitem &%-odq%&
-.oindex "&%-odq%&"
-.cindex "non-immediate delivery"
-.cindex "delivery" "suppressing immediate"
-.cindex "queueing incoming messages"
-This option applies to all modes in which Exim accepts incoming messages,
-including the listening daemon. It specifies that the accepting process should
-not automatically start a delivery process for each message received. Messages
-are placed in the queue, and remain there until a subsequent queue runner
-process encounters them. There are several configuration options (such as
-&%queue_only%&) that can be used to queue incoming messages under certain
-conditions. This option overrides all of them and also &%-odqs%&. It always
-forces queueing.
-
-.vitem &%-odqs%&
-.oindex "&%-odqs%&"
-.cindex "SMTP" "delaying delivery"
-.cindex "first pass routing"
-This option is a hybrid between &%-odb%&/&%-odi%& and &%-odq%&.
-However, like &%-odb%& and &%-odi%&, this option has no effect if
-&%queue_only_override%& is false and one of the queueing options in the
-configuration file is in effect.
-
-When &%-odqs%& does operate, a delivery process is started for each incoming
-message, in the background by default, but in the foreground if &%-odi%& is
-also present. The recipient addresses are routed, and local deliveries are done
-in the normal way. However, if any SMTP deliveries are required, they are not
-done at this time, so the message remains in the queue until a subsequent queue
-runner process encounters it. Because routing was done, Exim knows which
-messages are waiting for which hosts, and so a number of messages for the same
-host can be sent in a single SMTP connection. The &%queue_smtp_domains%&
-configuration option has the same effect for specific domains. See also the
-&%-qq%& option.
-
-.vitem &%-oee%&
-.oindex "&%-oee%&"
-.cindex "error" "reporting"
-If an error is detected while a non-SMTP message is being received (for
-example, a malformed address), the error is reported to the sender in a mail
-message.
-
-.cindex "return code" "for &%-oee%&"
-Provided
-this error message is successfully sent, the Exim receiving process
-exits with a return code of zero. If not, the return code is 2 if the problem
-is that the original message has no recipients, or 1 for any other error.
-This is the default &%-oe%&&'x'& option if Exim is called as &'rmail'&.
-
-.vitem &%-oem%&
-.oindex "&%-oem%&"
-.cindex "error" "reporting"
-.cindex "return code" "for &%-oem%&"
-This is the same as &%-oee%&, except that Exim always exits with a non-zero
-return code, whether or not the error message was successfully sent.
-This is the default &%-oe%&&'x'& option, unless Exim is called as &'rmail'&.
-
-.vitem &%-oep%&
-.oindex "&%-oep%&"
-.cindex "error" "reporting"
-If an error is detected while a non-SMTP message is being received, the
-error is reported by writing a message to the standard error file (stderr).
-.cindex "return code" "for &%-oep%&"
-The return code is 1 for all errors.
-
-.vitem &%-oeq%&
-.oindex "&%-oeq%&"
-.cindex "error" "reporting"
-This option is supported for compatibility with Sendmail, but has the same
-effect as &%-oep%&.
-
-.vitem &%-oew%&
-.oindex "&%-oew%&"
-.cindex "error" "reporting"
-This option is supported for compatibility with Sendmail, but has the same
-effect as &%-oem%&.
-
-.vitem &%-oi%&
-.oindex "&%-oi%&"
-.cindex "dot" "in incoming non-SMTP message"
-This option, which has the same effect as &%-i%&, specifies that a dot on a
-line by itself should not terminate an incoming, non-SMTP message. Otherwise, a
-single dot does terminate, though Exim does no special processing for other
-lines that start with a dot. This option is set by default if Exim is called as
-&'rmail'&. See also &%-ti%&.
-
-.vitem &%-oitrue%&
-.oindex "&%-oitrue%&"
-This option is treated as synonymous with &%-oi%&.
-
-.vitem &%-oMa%&&~<&'host&~address'&>
-.oindex "&%-oMa%&"
-.cindex "sender" "host address, specifying for local message"
-A number of options starting with &%-oM%& can be used to set values associated
-with remote hosts on locally-submitted messages (that is, messages not received
-over TCP/IP). These options can be used by any caller in conjunction with the
-&%-bh%&, &%-be%&, &%-bf%&, &%-bF%&, &%-bt%&, or &%-bv%& testing options. In
-other circumstances, they are ignored unless the caller is trusted.
-
-The &%-oMa%& option sets the sender host address. This may include a port
-number at the end, after a full stop (period). For example:
-.code
-exim -bs -oMa 10.9.8.7.1234
-.endd
-An alternative syntax is to enclose the IP address in square brackets,
-followed by a colon and the port number:
-.code
-exim -bs -oMa [10.9.8.7]:1234
-.endd
-The IP address is placed in the &$sender_host_address$& variable, and the
-port, if present, in &$sender_host_port$&. If both &%-oMa%& and &%-bh%&
-are present on the command line, the sender host IP address is taken from
-whichever one is last.
-
-.vitem &%-oMaa%&&~<&'name'&>
-.oindex "&%-oMaa%&"
-.cindex "authentication" "name, specifying for local message"
-See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMaa%&
-option sets the value of &$sender_host_authenticated$& (the authenticator
-name). See chapter &<<CHAPSMTPAUTH>>& for a discussion of SMTP authentication.
-This option can be used with &%-bh%& and &%-bs%& to set up an
-authenticated SMTP session without actually using the SMTP AUTH command.
-
-.vitem &%-oMai%&&~<&'string'&>
-.oindex "&%-oMai%&"
-.cindex "authentication" "id, specifying for local message"
-See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMai%&
-option sets the value of &$authenticated_id$& (the id that was authenticated).
-This overrides the default value (the caller's login id, except with &%-bh%&,
-where there is no default) for messages from local sources. See chapter
-&<<CHAPSMTPAUTH>>& for a discussion of authenticated ids.
-
-.vitem &%-oMas%&&~<&'address'&>
-.oindex "&%-oMas%&"
-.cindex "authentication" "sender, specifying for local message"
-See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMas%&
-option sets the authenticated sender value in &$authenticated_sender$&. It
-overrides the sender address that is created from the caller's login id for
-messages from local sources, except when &%-bh%& is used, when there is no
-default. For both &%-bh%& and &%-bs%&, an authenticated sender that is
-specified on a MAIL command overrides this value. See chapter
-&<<CHAPSMTPAUTH>>& for a discussion of authenticated senders.
-
-.vitem &%-oMi%&&~<&'interface&~address'&>
-.oindex "&%-oMi%&"
-.cindex "interface" "address, specifying for local message"
-See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMi%&
-option sets the IP interface address value. A port number may be included,
-using the same syntax as for &%-oMa%&. The interface address is placed in
-&$received_ip_address$& and the port number, if present, in &$received_port$&.
-
-.vitem &%-oMm%&&~<&'message&~reference'&>
-.oindex "&%-oMm%&"
-.cindex "message reference" "message reference, specifying for local message"
-See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMm%&
-option sets the message reference, e.g. message-id, and is logged during
-delivery. This is useful when some kind of audit trail is required to tie
-messages together. The format of the message reference is checked and will
-abort if the format is invalid. The option will only be accepted if exim is
-running in trusted mode, not as any regular user.
-
-The best example of a message reference is when Exim sends a bounce message.
-The message reference is the message-id of the original message for which Exim
-is sending the bounce.
-
-.vitem &%-oMr%&&~<&'protocol&~name'&>
-.oindex "&%-oMr%&"
-.cindex "protocol, specifying for local message"
-.vindex "&$received_protocol$&"
-See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMr%&
-option sets the received protocol value that is stored in
-&$received_protocol$&. However, it does not apply (and is ignored) when &%-bh%&
-or &%-bs%& is used. For &%-bh%&, the protocol is forced to one of the standard
-SMTP protocol names (see the description of &$received_protocol$& in section
-&<<SECTexpvar>>&). For &%-bs%&, the protocol is always &"local-"& followed by
-one of those same names. For &%-bS%& (batched SMTP) however, the protocol can
-be set by &%-oMr%&. Repeated use of this option is not supported.
-
-.vitem &%-oMs%&&~<&'host&~name'&>
-.oindex "&%-oMs%&"
-.cindex "sender" "host name, specifying for local message"
-See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMs%&
-option sets the sender host name in &$sender_host_name$&. When this option is
-present, Exim does not attempt to look up a host name from an IP address; it
-uses the name it is given.
-
-.vitem &%-oMt%&&~<&'ident&~string'&>
-.oindex "&%-oMt%&"
-.cindex "sender" "ident string, specifying for local message"
-See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMt%&
-option sets the sender ident value in &$sender_ident$&. The default setting for
-local callers is the login id of the calling process, except when &%-bh%& is
-used, when there is no default.
-
-.vitem &%-om%&
-.oindex "&%-om%&"
-.cindex "Sendmail compatibility" "&%-om%& option ignored"
-In Sendmail, this option means &"me too"&, indicating that the sender of a
-message should receive a copy of the message if the sender appears in an alias
-expansion. Exim always does this, so the option does nothing.
-
-.vitem &%-oo%&
-.oindex "&%-oo%&"
-.cindex "Sendmail compatibility" "&%-oo%& option ignored"
-This option is ignored. In Sendmail it specifies &"old style headers"&,
-whatever that means.
-
-.vitem &%-oP%&&~<&'path'&>
-.oindex "&%-oP%&"
-.cindex "pid (process id)" "of daemon"
-.cindex "daemon" "process id (pid)"
-This option is useful only in conjunction with &%-bd%& or &%-q%& with a time
-value. The option specifies the file to which the process id of the daemon is
-written. When &%-oX%& is used with &%-bd%&, or when &%-q%& with a time is used
-without &%-bd%&, this is the only way of causing Exim to write a pid file,
-because in those cases, the normal pid file is not used.
-
-.new
-.vitem &%-oPX%&
-.oindex "&%-oPX%&"
-.cindex "pid (process id)" "of daemon"
-.cindex "daemon" "process id (pid)"
-This option is not intended for general use.
-The daemon uses it when terminating due to a SIGTEM, possibly in
-combination with &%-oP%&&~<&'path'&>.
-It causes the pid file to be removed.
-.wen
-
-.vitem &%-or%&&~<&'time'&>
-.oindex "&%-or%&"
-.cindex "timeout" "for non-SMTP input"
-This option sets a timeout value for incoming non-SMTP messages. If it is not
-set, Exim will wait forever for the standard input. The value can also be set
-by the &%receive_timeout%& option. The format used for specifying times is
-described in section &<<SECTtimeformat>>&.
-
-.vitem &%-os%&&~<&'time'&>
-.oindex "&%-os%&"
-.cindex "timeout" "for SMTP input"
-.cindex "SMTP" "input timeout"
-This option sets a timeout value for incoming SMTP messages. The timeout
-applies to each SMTP command and block of data. The value can also be set by
-the &%smtp_receive_timeout%& option; it defaults to 5 minutes. The format used
-for specifying times is described in section &<<SECTtimeformat>>&.
-
-.vitem &%-ov%&
-.oindex "&%-ov%&"
-This option has exactly the same effect as &%-v%&.
-
-.vitem &%-oX%&&~<&'number&~or&~string'&>
-.oindex "&%-oX%&"
-.cindex "TCP/IP" "setting listening ports"
-.cindex "TCP/IP" "setting listening interfaces"
-.cindex "port" "receiving TCP/IP"
-This option is relevant only when the &%-bd%& (start listening daemon) option
-is also given. It controls which ports and interfaces the daemon uses. Details
-of the syntax, and how it interacts with configuration file options, are given
-in chapter &<<CHAPinterfaces>>&. When &%-oX%& is used to start a daemon, no pid
-file is written unless &%-oP%& is also present to specify a pid filename.
-
-.vitem &%-pd%&
-.oindex "&%-pd%&"
-.cindex "Perl" "starting the interpreter"
-This option applies when an embedded Perl interpreter is linked with Exim (see
-chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
-option, forcing the starting of the interpreter to be delayed until it is
-needed.
-
-.vitem &%-ps%&
-.oindex "&%-ps%&"
-.cindex "Perl" "starting the interpreter"
-This option applies when an embedded Perl interpreter is linked with Exim (see
-chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
-option, forcing the starting of the interpreter to occur as soon as Exim is
-started.
-
-.vitem &%-p%&<&'rval'&>:<&'sval'&>
-.oindex "&%-p%&"
-For compatibility with Sendmail, this option is equivalent to
-.display
-&`-oMr`& <&'rval'&> &`-oMs`& <&'sval'&>
-.endd
-It sets the incoming protocol and host name (for trusted callers). The
-host name and its colon can be omitted when only the protocol is to be set.
-Note the Exim already has two private options, &%-pd%& and &%-ps%&, that refer
-to embedded Perl. It is therefore impossible to set a protocol value of &`d`&
-or &`s`& using this option (but that does not seem a real limitation).
-Repeated use of this option is not supported.
-
-.vitem &%-q%&
-.oindex "&%-q%&"
-.cindex "queue runner" "starting manually"
-This option is normally restricted to admin users. However, there is a
-configuration option called &%prod_requires_admin%& which can be set false to
-relax this restriction (and also the same requirement for the &%-M%&, &%-R%&,
-and &%-S%& options).
-
-.cindex "queue runner" "description of operation"
-If other commandline options do not specify an action,
-the &%-q%& option starts one queue runner process. This scans the queue of
-waiting messages, and runs a delivery process for each one in turn. It waits
-for each delivery process to finish before starting the next one. A delivery
-process may not actually do any deliveries if the retry times for the addresses
-have not been reached. Use &%-qf%& (see below) if you want to override this.
-
-If
-.cindex "SMTP" "passed connection"
-.cindex "SMTP" "multiple deliveries"
-.cindex "multiple SMTP deliveries"
-the delivery process spawns other processes to deliver other messages down
-passed SMTP connections, the queue runner waits for these to finish before
-proceeding.
-
-When all the queued messages have been considered, the original queue runner
-process terminates. In other words, a single pass is made over the waiting
-mail, one message at a time. Use &%-q%& with a time (see below) if you want
-this to be repeated periodically.
-
-Exim processes the waiting messages in an unpredictable order. It isn't very
-random, but it is likely to be different each time, which is all that matters.
-If one particular message screws up a remote MTA, other messages to the same
-MTA have a chance of getting through if they get tried first.
-
-It is possible to cause the messages to be processed in lexical message id
-order, which is essentially the order in which they arrived, by setting the
-&%queue_run_in_order%& option, but this is not recommended for normal use.
-
-.vitem &%-q%&<&'qflags'&>
-The &%-q%& option may be followed by one or more flag letters that change its
-behaviour. They are all optional, but if more than one is present, they must
-appear in the correct order. Each flag is described in a separate item below.
-
-.vitem &%-qq...%&
-.oindex "&%-qq%&"
-.cindex "queue" "double scanning"
-.cindex "queue" "routing"
-.cindex "routing" "whole queue before delivery"
-.cindex "first pass routing"
-An option starting with &%-qq%& requests a two-stage queue run. In the first
-stage, the queue is scanned as if the &%queue_smtp_domains%& option matched
-every domain. Addresses are routed, local deliveries happen, but no remote
-transports are run.
-
-.new
-Performance will be best if the &%queue_run_in_order%& option is false.
-.wen
-
-.cindex "hints database" "remembering routing"
-The hints database that remembers which messages are waiting for specific hosts
-is updated, as if delivery to those hosts had been deferred. After this is
-complete, a second, normal queue scan happens, with routing and delivery taking
-place as normal. Messages that are routed to the same host should mostly be
-delivered down a single SMTP
-.cindex "SMTP" "passed connection"
-.cindex "SMTP" "multiple deliveries"
-.cindex "multiple SMTP deliveries"
-connection because of the hints that were set up during the first queue scan.
-This option may be useful for hosts that are connected to the Internet
-intermittently.
-
-.vitem &%-q[q]i...%&
-.oindex "&%-qi%&"
-.cindex "queue" "initial delivery"
-If the &'i'& flag is present, the queue runner runs delivery processes only for
-those messages that haven't previously been tried. (&'i'& stands for &"initial
-delivery"&.) This can be helpful if you are putting messages in the queue using
-&%-odq%& and want a queue runner just to process the new messages.
-
-.vitem &%-q[q][i]f...%&
-.oindex "&%-qf%&"
-.cindex "queue" "forcing delivery"
-.cindex "delivery" "forcing in queue run"
-If one &'f'& flag is present, a delivery attempt is forced for each non-frozen
-message, whereas without &'f'& only those non-frozen addresses that have passed
-their retry times are tried.
-
-.vitem &%-q[q][i]ff...%&
-.oindex "&%-qff%&"
-.cindex "frozen messages" "forcing delivery"
-If &'ff'& is present, a delivery attempt is forced for every message, whether
-frozen or not.
-
-.vitem &%-q[q][i][f[f]]l%&
-.oindex "&%-ql%&"
-.cindex "queue" "local deliveries only"
-The &'l'& (the letter &"ell"&) flag specifies that only local deliveries are to
-be done. If a message requires any remote deliveries, it remains in the queue
-for later delivery.
-
-.vitem &%-q[q][i][f[f]][l][G<name>[/<time>]]]%&
-.oindex "&%-qG%&"
-.cindex queue named
-.cindex "named queues"	"deliver from"
-.cindex "queue" "delivering specific messages"
-If the &'G'& flag and a name is present, the queue runner operates on the
-queue with the given name rather than the default queue.
-The name should not contain a &'/'& character.
-For a periodic queue run (see below)
-append to the name a slash and a time value.
-
-If other commandline options specify an action, a &'-qG<name>'& option
-will specify a queue to operate on.
-For example:
-.code
-exim -bp -qGquarantine
-mailq -qGquarantine
-exim -qGoffpeak -Rf @special.domain.example
-.endd
-
-.vitem &%-q%&<&'qflags'&>&~<&'start&~id'&>&~<&'end&~id'&>
-When scanning the queue, Exim can be made to skip over messages whose ids are
-lexically less than a given value by following the &%-q%& option with a
-starting message id. For example:
-.code
-exim -q 0t5C6f-0000c8-00
-.endd
-Messages that arrived earlier than &`0t5C6f-0000c8-00`& are not inspected. If a
-second message id is given, messages whose ids are lexically greater than it
-are also skipped. If the same id is given twice, for example,
-.code
-exim -q 0t5C6f-0000c8-00 0t5C6f-0000c8-00
-.endd
-just one delivery process is started, for that message. This differs from
-&%-M%& in that retry data is respected, and it also differs from &%-Mc%& in
-that it counts as a delivery from a queue run. Note that the selection
-mechanism does not affect the order in which the messages are scanned. There
-are also other ways of selecting specific sets of messages for delivery in a
-queue run &-- see &%-R%& and &%-S%&.
-
-.vitem &%-q%&<&'qflags'&><&'time'&>
-.cindex "queue runner" "starting periodically"
-.cindex "periodic queue running"
-When a time value is present, the &%-q%& option causes Exim to run as a daemon,
-starting a queue runner process at intervals specified by the given time value
-(whose format is described in section &<<SECTtimeformat>>&). This form of the
-&%-q%& option is commonly combined with the &%-bd%& option, in which case a
-single daemon process handles both functions. A common way of starting up a
-combined daemon at system boot time is to use a command such as
-.code
-/usr/exim/bin/exim -bd -q30m
-.endd
-Such a daemon listens for incoming SMTP calls, and also starts a queue runner
-process every 30 minutes.
-
-When a daemon is started by &%-q%& with a time value, but without &%-bd%&, no
-pid file is written unless one is explicitly requested by the &%-oP%& option.
-
-.vitem &%-qR%&<&'rsflags'&>&~<&'string'&>
-.oindex "&%-qR%&"
-This option is synonymous with &%-R%&. It is provided for Sendmail
-compatibility.
-
-.vitem &%-qS%&<&'rsflags'&>&~<&'string'&>
-.oindex "&%-qS%&"
-This option is synonymous with &%-S%&.
-
-.vitem &%-R%&<&'rsflags'&>&~<&'string'&>
-.oindex "&%-R%&"
-.cindex "queue runner" "for specific recipients"
-.cindex "delivery" "to given domain"
-.cindex "domain" "delivery to"
-The <&'rsflags'&> may be empty, in which case the white space before the string
-is optional, unless the string is &'f'&, &'ff'&, &'r'&, &'rf'&, or &'rff'&,
-which are the possible values for <&'rsflags'&>. White space is required if
-<&'rsflags'&> is not empty.
-
-This option is similar to &%-q%& with no time value, that is, it causes Exim to
-perform a single queue run, except that, when scanning the messages on the
-queue, Exim processes only those that have at least one undelivered recipient
-address containing the given string, which is checked in a case-independent
-way. If the <&'rsflags'&> start with &'r'&, <&'string'&> is interpreted as a
-regular expression; otherwise it is a literal string.
-
-If you want to do periodic queue runs for messages with specific recipients,
-you can combine &%-R%& with &%-q%& and a time value. For example:
-.code
-exim -q25m -R @special.domain.example
-.endd
-This example does a queue run for messages with recipients in the given domain
-every 25 minutes. Any additional flags that are specified with &%-q%& are
-applied to each queue run.
-
-Once a message is selected for delivery by this mechanism, all its addresses
-are processed. For the first selected message, Exim overrides any retry
-information and forces a delivery attempt for each undelivered address. This
-means that if delivery of any address in the first message is successful, any
-existing retry information is deleted, and so delivery attempts for that
-address in subsequently selected messages (which are processed without forcing)
-will run. However, if delivery of any address does not succeed, the retry
-information is updated, and in subsequently selected messages, the failing
-address will be skipped.
-
-.cindex "frozen messages" "forcing delivery"
-If the <&'rsflags'&> contain &'f'& or &'ff'&, the delivery forcing applies to
-all selected messages, not just the first; frozen messages are included when
-&'ff'& is present.
-
-The &%-R%& option makes it straightforward to initiate delivery of all messages
-to a given domain after a host has been down for some time. When the SMTP
-command ETRN is accepted by its ACL (see chapter &<<CHAPACL>>&), its default
-effect is to run Exim with the &%-R%& option, but it can be configured to run
-an arbitrary command instead.
-
-.vitem &%-r%&
-.oindex "&%-r%&"
-This is a documented (for Sendmail) obsolete alternative name for &%-f%&.
-
-.vitem &%-S%&<&'rsflags'&>&~<&'string'&>
-.oindex "&%-S%&"
-.cindex "delivery" "from given sender"
-.cindex "queue runner" "for specific senders"
-This option acts like &%-R%& except that it checks the string against each
-message's sender instead of against the recipients. If &%-R%& is also set, both
-conditions must be met for a message to be selected. If either of the options
-has &'f'& or &'ff'& in its flags, the associated action is taken.
-
-.vitem &%-Tqt%&&~<&'times'&>
-.oindex "&%-Tqt%&"
-This is an option that is exclusively for use by the Exim testing suite. It is not
-recognized when Exim is run normally. It allows for the setting up of explicit
-&"queue times"& so that various warning/retry features can be tested.
-
-.vitem &%-t%&
-.oindex "&%-t%&"
-.cindex "recipient" "extracting from header lines"
-.cindex "&'Bcc:'& header line"
-.cindex "&'Cc:'& header line"
-.cindex "&'To:'& header line"
-When Exim is receiving a locally-generated, non-SMTP message on its standard
-input, the &%-t%& option causes the recipients of the message to be obtained
-from the &'To:'&, &'Cc:'&, and &'Bcc:'& header lines in the message instead of
-from the command arguments. The addresses are extracted before any rewriting
-takes place and the &'Bcc:'& header line, if present, is then removed.
-
-.cindex "Sendmail compatibility" "&%-t%& option"
-If the command has any arguments, they specify addresses to which the message
-is &'not'& to be delivered. That is, the argument addresses are removed from
-the recipients list obtained from the headers. This is compatible with Smail 3
-and in accordance with the documented behaviour of several versions of
-Sendmail, as described in man pages on a number of operating systems (e.g.
-Solaris 8, IRIX 6.5, HP-UX 11). However, some versions of Sendmail &'add'&
-argument addresses to those obtained from the headers, and the O'Reilly
-Sendmail book documents it that way. Exim can be made to add argument addresses
-instead of subtracting them by setting the option
-&%extract_addresses_remove_arguments%& false.
-
-.cindex "&%Resent-%& header lines" "with &%-t%&"
-If there are any &%Resent-%& header lines in the message, Exim extracts
-recipients from all &'Resent-To:'&, &'Resent-Cc:'&, and &'Resent-Bcc:'& header
-lines instead of from &'To:'&, &'Cc:'&, and &'Bcc:'&. This is for compatibility
-with Sendmail and other MTAs. (Prior to release 4.20, Exim gave an error if
-&%-t%& was used in conjunction with &%Resent-%& header lines.)
-
-RFC 2822 talks about different sets of &%Resent-%& header lines (for when a
-message is resent several times). The RFC also specifies that they should be
-added at the front of the message, and separated by &'Received:'& lines. It is
-not at all clear how &%-t%& should operate in the present of multiple sets,
-nor indeed exactly what constitutes a &"set"&.
-In practice, it seems that MUAs do not follow the RFC. The &%Resent-%& lines
-are often added at the end of the header, and if a message is resent more than
-once, it is common for the original set of &%Resent-%& headers to be renamed as
-&%X-Resent-%& when a new set is added. This removes any possible ambiguity.
-
-.vitem &%-ti%&
-.oindex "&%-ti%&"
-This option is exactly equivalent to &%-t%& &%-i%&. It is provided for
-compatibility with Sendmail.
-
-.vitem &%-tls-on-connect%&
-.oindex "&%-tls-on-connect%&"
-.cindex "TLS" "use without STARTTLS"
-.cindex "TLS" "automatic start"
-This option is available when Exim is compiled with TLS support. It forces all
-incoming SMTP connections to behave as if the incoming port is listed in the
-&%tls_on_connect_ports%& option. See section &<<SECTsupobssmt>>& and chapter
-&<<CHAPTLS>>& for further details.
-
-
-.vitem &%-U%&
-.oindex "&%-U%&"
-.cindex "Sendmail compatibility" "&%-U%& option ignored"
-Sendmail uses this option for &"initial message submission"&, and its
-documentation states that in future releases, it may complain about
-syntactically invalid messages rather than fixing them when this flag is not
-set. Exim ignores this option.
-
-.vitem &%-v%&
-.oindex "&%-v%&"
-This option causes Exim to write information to the standard error stream,
-describing what it is doing. In particular, it shows the log lines for
-receiving and delivering a message, and if an SMTP connection is made, the SMTP
-dialogue is shown. Some of the log lines shown may not actually be written to
-the log if the setting of &%log_selector%& discards them. Any relevant
-selectors are shown with each log line. If none are shown, the logging is
-unconditional.
-
-.vitem &%-x%&
-.oindex "&%-x%&"
-AIX uses &%-x%& for a private purpose (&"mail from a local mail program has
-National Language Support extended characters in the body of the mail item"&).
-It sets &%-x%& when calling the MTA from its &%mail%& command. Exim ignores
-this option.
-
-.vitem &%-X%&&~<&'logfile'&>
-.oindex "&%-X%&"
-This option is interpreted by Sendmail to cause debug information to be sent
-to the named file.  It is ignored by Exim.
-
-.vitem &%-z%&&~<&'log-line'&>
-.oindex "&%-z%&"
-This option writes its argument to Exim's logfile.
-Use is restricted to administrators; the intent is for operational notes.
-Quotes should be used to maintain a multi-word item as a single argument,
-under most shells.
-.endlist
-
-.ecindex IIDclo1
-.ecindex IIDclo2
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. Insert a stylized DocBook comment here, to identify the end of the command
-. line options. This is for the benefit of the Perl script that automatically
-. creates a man page for the options.
-. ////////////////////////////////////////////////////////////////////////////
-
-.literal xml
-<!-- === End of command line options === -->
-.literal off
-
-
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-
-.chapter "The Exim runtime configuration file" "CHAPconf" &&&
-         "The runtime configuration file"
-
-.cindex "runtime configuration"
-.cindex "configuration file" "general description"
-.cindex "CONFIGURE_FILE"
-.cindex "configuration file" "errors in"
-.cindex "error" "in configuration file"
-.cindex "return code" "for bad configuration"
-Exim uses a single runtime configuration file that is read whenever an Exim
-binary is executed. Note that in normal operation, this happens frequently,
-because Exim is designed to operate in a distributed manner, without central
-control.
-
-If a syntax error is detected while reading the configuration file, Exim
-writes a message on the standard error, and exits with a non-zero return code.
-The message is also written to the panic log. &*Note*&: Only simple syntax
-errors can be detected at this time. The values of any expanded options are
-not checked until the expansion happens, even when the expansion does not
-actually alter the string.
-
-The name of the configuration file is compiled into the binary for security
-reasons, and is specified by the CONFIGURE_FILE compilation option. In
-most configurations, this specifies a single file. However, it is permitted to
-give a colon-separated list of filenames, in which case Exim uses the first
-existing file in the list.
-
-.cindex "EXIM_USER"
-.cindex "EXIM_GROUP"
-.cindex "CONFIGURE_OWNER"
-.cindex "CONFIGURE_GROUP"
-.cindex "configuration file" "ownership"
-.cindex "ownership" "configuration file"
-The runtime configuration file must be owned by root or by the user that is
-specified at compile time by the CONFIGURE_OWNER option (if set). The
-configuration file must not be world-writeable, or group-writeable unless its
-group is the root group or the one specified at compile time by the
-CONFIGURE_GROUP option.
-
-&*Warning*&: In a conventional configuration, where the Exim binary is setuid
-to root, anybody who is able to edit the runtime configuration file has an
-easy way to run commands as root. If you specify a user or group in the
-CONFIGURE_OWNER or CONFIGURE_GROUP options, then that user and/or any users
-who are members of that group will trivially be able to obtain root privileges.
-
-Up to Exim version 4.72, the runtime configuration file was also permitted to
-be writeable by the Exim user and/or group. That has been changed in Exim 4.73
-since it offered a simple privilege escalation for any attacker who managed to
-compromise the Exim user account.
-
-A default configuration file, which will work correctly in simple situations,
-is provided in the file &_src/configure.default_&. If CONFIGURE_FILE
-defines just one filename, the installation process copies the default
-configuration to a new file of that name if it did not previously exist. If
-CONFIGURE_FILE is a list, no default is automatically installed. Chapter
-&<<CHAPdefconfil>>& is a &"walk-through"& discussion of the default
-configuration.
-
-
-
-.section "Using a different configuration file" "SECID40"
-.cindex "configuration file" "alternate"
-A one-off alternate configuration can be specified by the &%-C%& command line
-option, which may specify a single file or a list of files. However, when
-&%-C%& is used, Exim gives up its root privilege, unless called by root (or
-unless the argument for &%-C%& is identical to the built-in value from
-CONFIGURE_FILE), or is listed in the TRUSTED_CONFIG_LIST file and the caller
-is the Exim user or the user specified in the CONFIGURE_OWNER setting. &%-C%&
-is useful mainly for checking the syntax of configuration files before
-installing them. No owner or group checks are done on a configuration file
-specified by &%-C%&, if root privilege has been dropped.
-
-Even the Exim user is not trusted to specify an arbitrary configuration file
-with the &%-C%& option to be used with root privileges, unless that file is
-listed in the TRUSTED_CONFIG_LIST file. This locks out the possibility of
-testing a configuration using &%-C%& right through message reception and
-delivery, even if the caller is root. The reception works, but by that time,
-Exim is running as the Exim user, so when it re-execs to regain privilege for
-the delivery, the use of &%-C%& causes privilege to be lost. However, root
-can test reception and delivery using two separate commands (one to put a
-message in the queue, using &%-odq%&, and another to do the delivery, using
-&%-M%&).
-
-If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
-prefix string with which any file named in a &%-C%& command line option must
-start. In addition, the filename must not contain the sequence &"&`/../`&"&.
-There is no default setting for ALT_CONFIG_PREFIX; when it is unset, any
-filename can be used with &%-C%&.
-
-One-off changes to a configuration can be specified by the &%-D%& command line
-option, which defines and overrides values for macros used inside the
-configuration file. However, like &%-C%&, the use of this option by a
-non-privileged user causes Exim to discard its root privilege.
-If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
-completely disabled, and its use causes an immediate error exit.
-
-The WHITELIST_D_MACROS option in &_Local/Makefile_& permits the binary builder
-to declare certain macro names trusted, such that root privilege will not
-necessarily be discarded.
-WHITELIST_D_MACROS defines a colon-separated list of macros which are
-considered safe and, if &%-D%& only supplies macros from this list, and the
-values are acceptable, then Exim will not give up root privilege if the caller
-is root, the Exim run-time user, or the CONFIGURE_OWNER, if set.  This is a
-transition mechanism and is expected to be removed in the future.  Acceptable
-values for the macros satisfy the regexp: &`^[A-Za-z0-9_/.-]*$`&
-
-Some sites may wish to use the same Exim binary on different machines that
-share a file system, but to use different configuration files on each machine.
-If CONFIGURE_FILE_USE_NODE is defined in &_Local/Makefile_&, Exim first
-looks for a file whose name is the configuration filename followed by a dot
-and the machine's node name, as obtained from the &[uname()]& function. If this
-file does not exist, the standard name is tried. This processing occurs for
-each filename in the list given by CONFIGURE_FILE or &%-C%&.
-
-In some esoteric situations different versions of Exim may be run under
-different effective uids and the CONFIGURE_FILE_USE_EUID is defined to
-help with this. See the comments in &_src/EDITME_& for details.
-
-
-
-.section "Configuration file format" "SECTconffilfor"
-.cindex "configuration file" "format of"
-.cindex "format" "configuration file"
-Exim's configuration file is divided into a number of different parts. General
-option settings must always appear at the start of the file. The other parts
-are all optional, and may appear in any order. Each part other than the first
-is introduced by the word &"begin"& followed by at least one literal
-space, and the name of the part. The optional parts are:
-
-.ilist
-&'ACL'&: Access control lists for controlling incoming SMTP mail (see chapter
-&<<CHAPACL>>&).
-.next
-.cindex "AUTH" "configuration"
-&'authenticators'&: Configuration settings for the authenticator drivers. These
-are concerned with the SMTP AUTH command (see chapter &<<CHAPSMTPAUTH>>&).
-.next
-&'routers'&: Configuration settings for the router drivers. Routers process
-addresses and determine how the message is to be delivered (see chapters
-&<<CHAProutergeneric>>&&--&<<CHAPredirect>>&).
-.next
-&'transports'&: Configuration settings for the transport drivers. Transports
-define mechanisms for copying messages to destinations (see chapters
-&<<CHAPtransportgeneric>>&&--&<<CHAPsmtptrans>>&).
-.next
-&'retry'&: Retry rules, for use when a message cannot be delivered immediately.
-If there is no retry section, or if it is empty (that is, no retry rules are
-defined), Exim will not retry deliveries. In this situation, temporary errors
-are treated the same as permanent errors. Retry rules are discussed in chapter
-&<<CHAPretry>>&.
-.next
-&'rewrite'&: Global address rewriting rules, for use when a message arrives and
-when new addresses are generated during delivery. Rewriting is discussed in
-chapter &<<CHAPrewrite>>&.
-.next
-&'local_scan'&: Private options for the &[local_scan()]& function. If you
-want to use this feature, you must set
-.code
-LOCAL_SCAN_HAS_OPTIONS=yes
-.endd
-in &_Local/Makefile_& before building Exim. Details of the &[local_scan()]&
-facility are given in chapter &<<CHAPlocalscan>>&.
-.endlist
-
-.cindex "configuration file" "leading white space in"
-.cindex "configuration file" "trailing white space in"
-.cindex "white space" "in configuration file"
-Leading and trailing white space in configuration lines is always ignored.
-
-Blank lines in the file, and lines starting with a # character (ignoring
-leading white space) are treated as comments and are ignored. &*Note*&: A
-# character other than at the beginning of a line is not treated specially,
-and does not introduce a comment.
-
-Any non-comment line can be continued by ending it with a backslash. Note that
-the general rule for white space means that trailing white space after the
-backslash and leading white space at the start of continuation
-lines is ignored. Comment lines beginning with # (but not empty lines) may
-appear in the middle of a sequence of continuation lines.
-
-A convenient way to create a configuration file is to start from the
-default, which is supplied in &_src/configure.default_&, and add, delete, or
-change settings as required.
-
-The ACLs, retry rules, and rewriting rules have their own syntax which is
-described in chapters &<<CHAPACL>>&, &<<CHAPretry>>&, and &<<CHAPrewrite>>&,
-respectively. The other parts of the configuration file have some syntactic
-items in common, and these are described below, from section &<<SECTcos>>&
-onwards. Before that, the inclusion, macro, and conditional facilities are
-described.
-
-
-
-.section "File inclusions in the configuration file" "SECID41"
-.cindex "inclusions in configuration file"
-.cindex "configuration file" "including other files"
-.cindex "&`.include`& in configuration file"
-.cindex "&`.include_if_exists`& in configuration file"
-You can include other files inside Exim's runtime configuration file by
-using this syntax:
-.display
-&`.include`& <&'filename'&>
-&`.include_if_exists`& <&'filename'&>
-.endd
-on a line by itself. Double quotes round the filename are optional. If you use
-the first form, a configuration error occurs if the file does not exist; the
-second form does nothing for non-existent files.
-The first form allows a relative name. It is resolved relative to
-the directory of the including file. For the second form an absolute filename
-is required.
-
-Includes may be nested to any depth, but remember that Exim reads its
-configuration file often, so it is a good idea to keep them to a minimum.
-If you change the contents of an included file, you must HUP the daemon,
-because an included file is read only when the configuration itself is read.
-
-The processing of inclusions happens early, at a physical line level, so, like
-comment lines, an inclusion can be used in the middle of an option setting,
-for example:
-.code
-hosts_lookup = a.b.c \
-               .include /some/file
-.endd
-Include processing happens after macro processing (see below). Its effect is to
-process the lines of the included file as if they occurred inline where the
-inclusion appears.
-
-
-
-.section "Macros in the configuration file" "SECTmacrodefs"
-.cindex "macro" "description of"
-.cindex "configuration file" "macros"
-If a line in the main part of the configuration (that is, before the first
-&"begin"& line) begins with an upper case letter, it is taken as a macro
-definition, and must be of the form
-.display
-<&'name'&> = <&'rest of line'&>
-.endd
-The name must consist of letters, digits, and underscores, and need not all be
-in upper case, though that is recommended. The rest of the line, including any
-continuations, is the replacement text, and has leading and trailing white
-space removed. Quotes are not removed. The replacement text can never end with
-a backslash character, but this doesn't seem to be a serious limitation.
-
-Macros may also be defined between router, transport, authenticator, or ACL
-definitions. They may not, however, be defined within an individual driver or
-ACL, or in the &%local_scan%&, retry, or rewrite sections of the configuration.
-
-.section "Macro substitution" "SECID42"
-Once a macro is defined, all subsequent lines in the file (and any included
-files) are scanned for the macro name; if there are several macros, the line is
-scanned for each, in turn, in the order in which the macros are defined. The
-replacement text is not re-scanned for the current macro, though it is scanned
-for subsequently defined macros. For this reason, a macro name may not contain
-the name of a previously defined macro as a substring. You could, for example,
-define
-.display
-&`ABCD_XYZ = `&<&'something'&>
-&`ABCD = `&<&'something else'&>
-.endd
-but putting the definitions in the opposite order would provoke a configuration
-error. Macro expansion is applied to individual physical lines from the file,
-before checking for line continuation or file inclusion (see above). If a line
-consists solely of a macro name, and the expansion of the macro is empty, the
-line is ignored. A macro at the start of a line may turn the line into a
-comment line or a &`.include`& line.
-
-
-.section "Redefining macros" "SECID43"
-Once defined, the value of a macro can be redefined later in the configuration
-(or in an included file). Redefinition is specified by using &'=='& instead of
-&'='&. For example:
-.code
-MAC =  initial value
-...
-MAC == updated value
-.endd
-Redefinition does not alter the order in which the macros are applied to the
-subsequent lines of the configuration file. It is still the same order in which
-the macros were originally defined. All that changes is the macro's value.
-Redefinition makes it possible to accumulate values. For example:
-.code
-MAC =  initial value
-...
-MAC == MAC and something added
-.endd
-This can be helpful in situations where the configuration file is built
-from a number of other files.
-
-.section "Overriding macro values" "SECID44"
-The values set for macros in the configuration file can be overridden by the
-&%-D%& command line option, but Exim gives up its root privilege when &%-D%& is
-used, unless called by root or the Exim user. A definition on the command line
-using the &%-D%& option causes all definitions and redefinitions within the
-file to be ignored.
-
-
-
-.section "Example of macro usage" "SECID45"
-As an example of macro usage, consider a configuration where aliases are looked
-up in a MySQL database. It helps to keep the file less cluttered if long
-strings such as SQL statements are defined separately as macros, for example:
-.code
-ALIAS_QUERY = select mailbox from user where \
-              login='${quote_mysql:$local_part}';
-.endd
-This can then be used in a &(redirect)& router setting like this:
-.code
-data = ${lookup mysql{ALIAS_QUERY}}
-.endd
-In earlier versions of Exim macros were sometimes used for domain, host, or
-address lists. In Exim 4 these are handled better by named lists &-- see
-section &<<SECTnamedlists>>&.
-
-
-.section "Builtin macros" "SECTbuiltinmacros"
-Exim defines some macros depending on facilities available, which may
-differ due to build-time definitions and from one release to another.
-All of these macros start with an underscore.
-They can be used to conditionally include parts of a configuration
-(see below).
-
-The following classes of macros are defined:
-.display
-&` _HAVE_*                    `&  build-time defines
-&` _DRIVER_ROUTER_*           `&  router drivers
-&` _DRIVER_TRANSPORT_*        `&  transport drivers
-&` _DRIVER_AUTHENTICATOR_*    `&  authenticator drivers
-&` _LOG_*                     `&  log_selector values
-&` _OPT_MAIN_*                `&  main config options
-&` _OPT_ROUTERS_*             `&  generic router options
-&` _OPT_TRANSPORTS_*          `&  generic transport options
-&` _OPT_AUTHENTICATORS_*      `&  generic authenticator options
-&` _OPT_ROUTER_*_*            `&  private router options
-&` _OPT_TRANSPORT_*_*         `&  private transport options
-&` _OPT_AUTHENTICATOR_*_*     `&  private authenticator options
-.endd
-
-Use an &"exim -bP macros"& command to get the list of macros.
-
-
-.section "Conditional skips in the configuration file" "SECID46"
-.cindex "configuration file" "conditional skips"
-.cindex "&`.ifdef`&"
-You can use the directives &`.ifdef`&, &`.ifndef`&, &`.elifdef`&,
-&`.elifndef`&, &`.else`&, and &`.endif`& to dynamically include or exclude
-portions of the configuration file. The processing happens whenever the file is
-read (that is, when an Exim binary starts to run).
-
-The implementation is very simple. Instances of the first four directives must
-be followed by text that includes the names of one or macros. The condition
-that is tested is whether or not any macro substitution has taken place in the
-line. Thus:
-.code
-.ifdef AAA
-message_size_limit = 50M
-.else
-message_size_limit = 100M
-.endif
-.endd
-sets a message size limit of 50M if the macro &`AAA`& is defined
-(or &`A`& or &`AA`&), and 100M
-otherwise. If there is more than one macro named on the line, the condition
-is true if any of them are defined. That is, it is an &"or"& condition. To
-obtain an &"and"& condition, you need to use nested &`.ifdef`&s.
-
-Although you can use a macro expansion to generate one of these directives,
-it is not very useful, because the condition &"there was a macro substitution
-in this line"& will always be true.
-
-Text following &`.else`& and &`.endif`& is ignored, and can be used as comment
-to clarify complicated nestings.
-
-
-
-.section "Common option syntax" "SECTcos"
-.cindex "common option syntax"
-.cindex "syntax of common options"
-.cindex "configuration file" "common option syntax"
-For the main set of options, driver options, and &[local_scan()]& options,
-each setting is on a line by itself, and starts with a name consisting of
-lower-case letters and underscores. Many options require a data value, and in
-these cases the name must be followed by an equals sign (with optional white
-space) and then the value. For example:
-.code
-qualify_domain = mydomain.example.com
-.endd
-.cindex "hiding configuration option values"
-.cindex "configuration options" "hiding value of"
-.cindex "options" "hiding value of"
-Some option settings may contain sensitive data, for example, passwords for
-accessing databases. To stop non-admin users from using the &%-bP%& command
-line option to read these values, you can precede the option settings with the
-word &"hide"&. For example:
-.code
-hide mysql_servers = localhost/users/admin/secret-password
-.endd
-For non-admin users, such options are displayed like this:
-.code
-mysql_servers = <value not displayable>
-.endd
-If &"hide"& is used on a driver option, it hides the value of that option on
-all instances of the same driver.
-
-The following sections describe the syntax used for the different data types
-that are found in option settings.
-
-
-.section "Boolean options" "SECID47"
-.cindex "format" "boolean"
-.cindex "boolean configuration values"
-.oindex "&%no_%&&'xxx'&"
-.oindex "&%not_%&&'xxx'&"
-Options whose type is given as boolean are on/off switches. There are two
-different ways of specifying such options: with and without a data value. If
-the option name is specified on its own without data, the switch is turned on;
-if it is preceded by &"no_"& or &"not_"& the switch is turned off. However,
-boolean options may be followed by an equals sign and one of the words
-&"true"&, &"false"&, &"yes"&, or &"no"&, as an alternative syntax. For example,
-the following two settings have exactly the same effect:
-.code
-queue_only
-queue_only = true
-.endd
-The following two lines also have the same (opposite) effect:
-.code
-no_queue_only
-queue_only = false
-.endd
-You can use whichever syntax you prefer.
-
-
-
-
-.section "Integer values" "SECID48"
-.cindex "integer configuration values"
-.cindex "format" "integer"
-If an option's type is given as &"integer"&, the value can be given in decimal,
-hexadecimal, or octal. If it starts with a digit greater than zero, a decimal
-number is assumed. Otherwise, it is treated as an octal number unless it starts
-with the characters &"0x"&, in which case the remainder is interpreted as a
-hexadecimal number.
-
-If an integer value is followed by the letter K, it is multiplied by 1024; if
-it is followed by the letter M, it is multiplied by 1024x1024;
-if by the letter G, 1024x1024x1024.
-When the values
-of integer option settings are output, values which are an exact multiple of
-1024 or 1024x1024 are sometimes, but not always, printed using the letters K
-and M. The printing style is independent of the actual input format that was
-used.
-
-
-.section "Octal integer values" "SECID49"
-.cindex "integer format"
-.cindex "format" "octal integer"
-If an option's type is given as &"octal integer"&, its value is always
-interpreted as an octal number, whether or not it starts with the digit zero.
-Such options are always output in octal.
-
-
-.section "Fixed point numbers" "SECID50"
-.cindex "fixed point configuration values"
-.cindex "format" "fixed point"
-If an option's type is given as &"fixed-point"&, its value must be a decimal
-integer, optionally followed by a decimal point and up to three further digits.
-
-
-
-.section "Time intervals" "SECTtimeformat"
-.cindex "time interval" "specifying in configuration"
-.cindex "format" "time interval"
-A time interval is specified as a sequence of numbers, each followed by one of
-the following letters, with no intervening white space:
-
-.table2 30pt
-.irow &%s%& seconds
-.irow &%m%& minutes
-.irow &%h%& hours
-.irow &%d%& days
-.irow &%w%& weeks
-.endtable
-
-For example, &"3h50m"& specifies 3 hours and 50 minutes. The values of time
-intervals are output in the same format. Exim does not restrict the values; it
-is perfectly acceptable, for example, to specify &"90m"& instead of &"1h30m"&.
-
-
-
-.section "String values" "SECTstrings"
-.cindex "string" "format of configuration values"
-.cindex "format" "string"
-If an option's type is specified as &"string"&, the value can be specified with
-or without double-quotes. If it does not start with a double-quote, the value
-consists of the remainder of the line plus any continuation lines, starting at
-the first character after any leading white space, with trailing white space
-removed, and with no interpretation of the characters in the string. Because
-Exim removes comment lines (those beginning with #) at an early stage, they can
-appear in the middle of a multi-line string. The following two settings are
-therefore equivalent:
-.code
-trusted_users = uucp:mail
-trusted_users = uucp:\
-                # This comment line is ignored
-                mail
-.endd
-.cindex "string" "quoted"
-.cindex "escape characters in quoted strings"
-If a string does start with a double-quote, it must end with a closing
-double-quote, and any backslash characters other than those used for line
-continuation are interpreted as escape characters, as follows:
-
-.table2 100pt
-.irow &`\\`&                     "single backslash"
-.irow &`\n`&                     "newline"
-.irow &`\r`&                     "carriage return"
-.irow &`\t`&                     "tab"
-.irow "&`\`&<&'octal digits'&>"  "up to 3 octal digits specify one character"
-.irow "&`\x`&<&'hex digits'&>"   "up to 2 hexadecimal digits specify one &&&
-                                   character"
-.endtable
-
-If a backslash is followed by some other character, including a double-quote
-character, that character replaces the pair.
-
-Quoting is necessary only if you want to make use of the backslash escapes to
-insert special characters, or if you need to specify a value with leading or
-trailing spaces. These cases are rare, so quoting is almost never needed in
-current versions of Exim. In versions of Exim before 3.14, quoting was required
-in order to continue lines, so you may come across older configuration files
-and examples that apparently quote unnecessarily.
-
-
-.section "Expanded strings" "SECID51"
-.cindex "expansion" "definition of"
-Some strings in the configuration file are subjected to &'string expansion'&,
-by which means various parts of the string may be changed according to the
-circumstances (see chapter &<<CHAPexpand>>&). The input syntax for such strings
-is as just described; in particular, the handling of backslashes in quoted
-strings is done as part of the input process, before expansion takes place.
-However, backslash is also an escape character for the expander, so any
-backslashes that are required for that reason must be doubled if they are
-within a quoted configuration string.
-
-
-.section "User and group names" "SECID52"
-.cindex "user name" "format of"
-.cindex "format" "user name"
-.cindex "groups" "name format"
-.cindex "format" "group name"
-User and group names are specified as strings, using the syntax described
-above, but the strings are interpreted specially. A user or group name must
-either consist entirely of digits, or be a name that can be looked up using the
-&[getpwnam()]& or &[getgrnam()]& function, as appropriate.
-
-
-.section "List construction" "SECTlistconstruct"
-.cindex "list" "syntax of in configuration"
-.cindex "format" "list item in configuration"
-.cindex "string" "list, definition of"
-The data for some configuration options is a list of items, with colon as the
-default separator. Many of these options are shown with type &"string list"& in
-the descriptions later in this document. Others are listed as &"domain list"&,
-&"host list"&, &"address list"&, or &"local part list"&. Syntactically, they
-are all the same; however, those other than &"string list"& are subject to
-particular kinds of interpretation, as described in chapter
-&<<CHAPdomhosaddlists>>&.
-
-In all these cases, the entire list is treated as a single string as far as the
-input syntax is concerned. The &%trusted_users%& setting in section
-&<<SECTstrings>>& above is an example. If a colon is actually needed in an item
-in a list, it must be entered as two colons. Leading and trailing white space
-on each item in a list is ignored. This makes it possible to include items that
-start with a colon, and in particular, certain forms of IPv6 address. For
-example, the list
-.code
-local_interfaces = 127.0.0.1 : ::::1
-.endd
-contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address ::1.
-
-&*Note*&: Although leading and trailing white space is ignored in individual
-list items, it is not ignored when parsing the list. The space after the first
-colon in the example above is necessary. If it were not there, the list would
-be interpreted as the two items 127.0.0.1:: and 1.
-
-.section "Changing list separators" "SECTlistsepchange"
-.cindex "list separator" "changing"
-.cindex "IPv6" "addresses in lists"
-Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was
-introduced to allow the separator character to be changed. If a list begins
-with a left angle bracket, followed by any punctuation character, that
-character is used instead of colon as the list separator. For example, the list
-above can be rewritten to use a semicolon separator like this:
-.code
-local_interfaces = <; 127.0.0.1 ; ::1
-.endd
-This facility applies to all lists, with the exception of the list in
-&%log_file_path%&. It is recommended that the use of non-colon separators be
-confined to circumstances where they really are needed.
-
-.cindex "list separator" "newline as"
-.cindex "newline" "as list separator"
-It is also possible to use newline and other control characters (those with
-code values less than 32, plus DEL) as separators in lists. Such separators
-must be provided literally at the time the list is processed. For options that
-are string-expanded, you can write the separator using a normal escape
-sequence. This will be processed by the expander before the string is
-interpreted as a list. For example, if a newline-separated list of domains is
-generated by a lookup, you can process it directly by a line such as this:
-.code
-domains = <\n ${lookup mysql{.....}}
-.endd
-This avoids having to change the list separator in such data. You are unlikely
-to want to use a control character as a separator in an option that is not
-expanded, because the value is literal text. However, it can be done by giving
-the value in quotes. For example:
-.code
-local_interfaces = "<\n 127.0.0.1 \n ::1"
-.endd
-Unlike printing character separators, which can be included in list items by
-doubling, it is not possible to include a control character as data when it is
-set as the separator. Two such characters in succession are interpreted as
-enclosing an empty list item.
-
-
-
-.section "Empty items in lists" "SECTempitelis"
-.cindex "list" "empty item in"
-An empty item at the end of a list is always ignored. In other words, trailing
-separator characters are ignored. Thus, the list in
-.code
-senders = user@domain :
-.endd
-contains only a single item. If you want to include an empty string as one item
-in a list, it must not be the last item. For example, this list contains three
-items, the second of which is empty:
-.code
-senders = user1@domain : : user2@domain
-.endd
-&*Note*&: There must be white space between the two colons, as otherwise they
-are interpreted as representing a single colon data character (and the list
-would then contain just one item). If you want to specify a list that contains
-just one, empty item, you can do it as in this example:
-.code
-senders = :
-.endd
-In this case, the first item is empty, and the second is discarded because it
-is at the end of the list.
-
-
-
-
-.section "Format of driver configurations" "SECTfordricon"
-.cindex "drivers" "configuration format"
-There are separate parts in the configuration for defining routers, transports,
-and authenticators. In each part, you are defining a number of driver
-instances, each with its own set of options. Each driver instance is defined by
-a sequence of lines like this:
-.display
-<&'instance name'&>:
-  <&'option'&>
-  ...
-  <&'option'&>
-.endd
-In the following example, the instance name is &(localuser)&, and it is
-followed by three options settings:
-.code
-localuser:
-  driver = accept
-  check_local_user
-  transport = local_delivery
-.endd
-For each driver instance, you specify which Exim code module it uses &-- by the
-setting of the &%driver%& option &-- and (optionally) some configuration
-settings. For example, in the case of transports, if you want a transport to
-deliver with SMTP you would use the &(smtp)& driver; if you want to deliver to
-a local file you would use the &(appendfile)& driver. Each of the drivers is
-described in detail in its own separate chapter later in this manual.
-
-You can have several routers, transports, or authenticators that are based on
-the same underlying driver (each must have a different instance name).
-
-The order in which routers are defined is important, because addresses are
-passed to individual routers one by one, in order. The order in which
-transports are defined does not matter at all. The order in which
-authenticators are defined is used only when Exim, as a client, is searching
-them to find one that matches an authentication mechanism offered by the
-server.
-
-.cindex "generic options"
-.cindex "options" "generic &-- definition of"
-Within a driver instance definition, there are two kinds of option: &'generic'&
-and &'private'&. The generic options are those that apply to all drivers of the
-same type (that is, all routers, all transports or all authenticators). The
-&%driver%& option is a generic option that must appear in every definition.
-.cindex "private options"
-The private options are special for each driver, and none need appear, because
-they all have default values.
-
-The options may appear in any order, except that the &%driver%& option must
-precede any private options, since these depend on the particular driver. For
-this reason, it is recommended that &%driver%& always be the first option.
-
-Driver instance names, which are used for reference in log entries and
-elsewhere, can be any sequence of letters, digits, and underscores (starting
-with a letter) and must be unique among drivers of the same type. A router and
-a transport (for example) can each have the same name, but no two router
-instances can have the same name. The name of a driver instance should not be
-confused with the name of the underlying driver module. For example, the
-configuration lines:
-.code
-remote_smtp:
-  driver = smtp
-.endd
-create an instance of the &(smtp)& transport driver whose name is
-&(remote_smtp)&. The same driver code can be used more than once, with
-different instance names and different option settings each time. A second
-instance of the &(smtp)& transport, with different options, might be defined
-thus:
-.code
-special_smtp:
-  driver = smtp
-  port = 1234
-  command_timeout = 10s
-.endd
-The names &(remote_smtp)& and &(special_smtp)& would be used to reference
-these transport instances from routers, and these names would appear in log
-lines.
-
-Comment lines may be present in the middle of driver specifications. The full
-list of option settings for any particular driver instance, including all the
-defaulted values, can be extracted by making use of the &%-bP%& command line
-option.
-
-
-
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "The default configuration file" "CHAPdefconfil"
-.scindex IIDconfiwal "configuration file" "default &""walk through""&"
-.cindex "default" "configuration file &""walk through""&"
-The default configuration file supplied with Exim as &_src/configure.default_&
-is sufficient for a host with simple mail requirements. As an introduction to
-the way Exim is configured, this chapter &"walks through"& the default
-configuration, giving brief explanations of the settings. Detailed descriptions
-of the options are given in subsequent chapters. The default configuration file
-itself contains extensive comments about ways you might want to modify the
-initial settings. However, note that there are many options that are not
-mentioned at all in the default configuration.
-
-
-
-.section "Macros" "SECTdefconfmacros"
-All macros should be defined before any options.
-
-One macro is specified, but commented out, in the default configuration:
-.code
-# ROUTER_SMARTHOST=MAIL.HOSTNAME.FOR.CENTRAL.SERVER.EXAMPLE
-.endd
-If all off-site mail is expected to be delivered to a "smarthost", then set the
-hostname here and uncomment the macro.  This will affect which router is used
-later on.  If this is left commented out, then Exim will perform direct-to-MX
-deliveries using a &(dnslookup)& router.
-
-In addition to macros defined here, Exim includes a number of built-in macros
-to enable configuration to be guarded by a binary built with support for a
-given feature.  See section &<<SECTbuiltinmacros>>& for more details.
-
-
-.section "Main configuration settings" "SECTdefconfmain"
-The main (global) configuration option settings section must always come first
-in the file, after the macros.
-The first thing you'll see in the file, after some initial comments, is the line
-.code
-# primary_hostname =
-.endd
-This is a commented-out setting of the &%primary_hostname%& option. Exim needs
-to know the official, fully qualified name of your host, and this is where you
-can specify it. However, in most cases you do not need to set this option. When
-it is unset, Exim uses the &[uname()]& system function to obtain the host name.
-
-The first three non-comment configuration lines are as follows:
-.code
-domainlist local_domains    = @
-domainlist relay_to_domains =
-hostlist   relay_from_hosts = 127.0.0.1
-.endd
-These are not, in fact, option settings. They are definitions of two named
-domain lists and one named host list. Exim allows you to give names to lists of
-domains, hosts, and email addresses, in order to make it easier to manage the
-configuration file (see section &<<SECTnamedlists>>&).
-
-The first line defines a domain list called &'local_domains'&; this is used
-later in the configuration to identify domains that are to be delivered
-on the local host.
-
-.cindex "@ in a domain list"
-There is just one item in this list, the string &"@"&. This is a special form
-of entry which means &"the name of the local host"&. Thus, if the local host is
-called &'a.host.example'&, mail to &'any.user@a.host.example'& is expected to
-be delivered locally. Because the local host's name is referenced indirectly,
-the same configuration file can be used on different hosts.
-
-The second line defines a domain list called &'relay_to_domains'&, but the
-list itself is empty. Later in the configuration we will come to the part that
-controls mail relaying through the local host; it allows relaying to any
-domains in this list. By default, therefore, no relaying on the basis of a mail
-domain is permitted.
-
-The third line defines a host list called &'relay_from_hosts'&. This list is
-used later in the configuration to permit relaying from any host or IP address
-that matches the list. The default contains just the IP address of the IPv4
-loopback interface, which means that processes on the local host are able to
-submit mail for relaying by sending it over TCP/IP to that interface. No other
-hosts are permitted to submit messages for relaying.
-
-Just to be sure there's no misunderstanding: at this point in the configuration
-we aren't actually setting up any controls. We are just defining some domains
-and hosts that will be used in the controls that are specified later.
-
-The next two configuration lines are genuine option settings:
-.code
-acl_smtp_rcpt = acl_check_rcpt
-acl_smtp_data = acl_check_data
-.endd
-These options specify &'Access Control Lists'& (ACLs) that are to be used
-during an incoming SMTP session for every recipient of a message (every RCPT
-command), and after the contents of the message have been received,
-respectively. The names of the lists are &'acl_check_rcpt'& and
-&'acl_check_data'&, and we will come to their definitions below, in the ACL
-section of the configuration. The RCPT ACL controls which recipients are
-accepted for an incoming message &-- if a configuration does not provide an ACL
-to check recipients, no SMTP mail can be accepted. The DATA ACL allows the
-contents of a message to be checked.
-
-Two commented-out option settings are next:
-.code
-# av_scanner = clamd:/tmp/clamd
-# spamd_address = 127.0.0.1 783
-.endd
-These are example settings that can be used when Exim is compiled with the
-content-scanning extension. The first specifies the interface to the virus
-scanner, and the second specifies the interface to SpamAssassin. Further
-details are given in chapter &<<CHAPexiscan>>&.
-
-Three more commented-out option settings follow:
-.code
-# tls_advertise_hosts = *
-# tls_certificate = /etc/ssl/exim.crt
-# tls_privatekey = /etc/ssl/exim.pem
-.endd
-These are example settings that can be used when Exim is compiled with
-support for TLS (aka SSL) as described in section &<<SECTinctlsssl>>&. The
-first one specifies the list of clients that are allowed to use TLS when
-connecting to this server; in this case, the wildcard means all clients. The
-other options specify where Exim should find its TLS certificate and private
-key, which together prove the server's identity to any clients that connect.
-More details are given in chapter &<<CHAPTLS>>&.
-
-Another two commented-out option settings follow:
-.code
-# daemon_smtp_ports = 25 : 465 : 587
-# tls_on_connect_ports = 465
-.endd
-.cindex "port" "465 and 587"
-.cindex "port" "for message submission"
-.cindex "message" "submission, ports for"
-.cindex "submissions protocol"
-.cindex "smtps protocol"
-.cindex "ssmtp protocol"
-.cindex "SMTP" "submissions protocol"
-.cindex "SMTP" "ssmtp protocol"
-.cindex "SMTP" "smtps protocol"
-These options provide better support for roaming users who wish to use this
-server for message submission. They are not much use unless you have turned on
-TLS (as described in the previous paragraph) and authentication (about which
-more in section &<<SECTdefconfauth>>&).
-Mail submission from mail clients (MUAs) should be separate from inbound mail
-to your domain (MX delivery) for various good reasons (eg, ability to impose
-much saner TLS protocol and ciphersuite requirements without unintended
-consequences).
-RFC 6409 (previously 4409) specifies use of port 587 for SMTP Submission,
-which uses STARTTLS, so this is the &"submission"& port.
-RFC 8314 specifies use of port 465 as the &"submissions"& protocol,
-which should be used in preference to 587.
-You should also consider deploying SRV records to help clients find
-these ports.
-Older names for &"submissions"& are &"smtps"& and &"ssmtp"&.
-
-Two more commented-out options settings follow:
-.code
-# qualify_domain =
-# qualify_recipient =
-.endd
-The first of these specifies a domain that Exim uses when it constructs a
-complete email address from a local login name. This is often needed when Exim
-receives a message from a local process. If you do not set &%qualify_domain%&,
-the value of &%primary_hostname%& is used. If you set both of these options,
-you can have different qualification domains for sender and recipient
-addresses. If you set only the first one, its value is used in both cases.
-
-.cindex "domain literal" "recognizing format"
-The following line must be uncommented if you want Exim to recognize
-addresses of the form &'user@[10.11.12.13]'& that is, with a &"domain literal"&
-(an IP address within square brackets) instead of a named domain.
-.code
-# allow_domain_literals
-.endd
-The RFCs still require this form, but many people think that in the modern
-Internet it makes little sense to permit mail to be sent to specific hosts by
-quoting their IP addresses. This ancient format has been used by people who
-try to abuse hosts by using them for unwanted relaying. However, some
-people believe there are circumstances (for example, messages addressed to
-&'postmaster'&) where domain literals are still useful.
-
-The next configuration line is a kind of trigger guard:
-.code
-never_users = root
-.endd
-It specifies that no delivery must ever be run as the root user. The normal
-convention is to set up &'root'& as an alias for the system administrator. This
-setting is a guard against slips in the configuration.
-The list of users specified by &%never_users%& is not, however, the complete
-list; the build-time configuration in &_Local/Makefile_& has an option called
-FIXED_NEVER_USERS specifying a list that cannot be overridden. The
-contents of &%never_users%& are added to this list. By default
-FIXED_NEVER_USERS also specifies root.
-
-When a remote host connects to Exim in order to send mail, the only information
-Exim has about the host's identity is its IP address. The next configuration
-line,
-.code
-host_lookup = *
-.endd
-specifies that Exim should do a reverse DNS lookup on all incoming connections,
-in order to get a host name. This improves the quality of the logging
-information, but if you feel it is too expensive, you can remove it entirely,
-or restrict the lookup to hosts on &"nearby"& networks.
-Note that it is not always possible to find a host name from an IP address,
-because not all DNS reverse zones are maintained, and sometimes DNS servers are
-unreachable.
-
-The next two lines are concerned with &'ident'& callbacks, as defined by RFC
-1413 (hence their names):
-.code
-rfc1413_hosts = *
-rfc1413_query_timeout = 0s
-.endd
-These settings cause Exim to avoid ident callbacks for all incoming SMTP calls.
-Few hosts offer RFC1413 service these days; calls have to be
-terminated by a timeout and this needlessly delays the startup
-of an incoming SMTP connection.
-If you have hosts for which you trust RFC1413 and need this
-information, you can change this.
-
-This line enables an efficiency SMTP option.  It is negotiated by clients
-and not expected to cause problems but can be disabled if needed.
-.code
-prdr_enable = true
-.endd
-
-When Exim receives messages over SMTP connections, it expects all addresses to
-be fully qualified with a domain, as required by the SMTP definition. However,
-if you are running a server to which simple clients submit messages, you may
-find that they send unqualified addresses. The two commented-out options:
-.code
-# sender_unqualified_hosts =
-# recipient_unqualified_hosts =
-.endd
-show how you can specify hosts that are permitted to send unqualified sender
-and recipient addresses, respectively.
-
-The &%log_selector%& option is used to increase the detail of logging
-over the default:
-.code
-log_selector = +smtp_protocol_error +smtp_syntax_error \
-               +tls_certificate_verified
-.endd
-
-The &%percent_hack_domains%& option is also commented out:
-.code
-# percent_hack_domains =
-.endd
-It provides a list of domains for which the &"percent hack"& is to operate.
-This is an almost obsolete form of explicit email routing. If you do not know
-anything about it, you can safely ignore this topic.
-
-The next two settings in the main part of the default configuration are
-concerned with messages that have been &"frozen"& on Exim's queue. When a
-message is frozen, Exim no longer continues to try to deliver it. Freezing
-occurs when a bounce message encounters a permanent failure because the sender
-address of the original message that caused the bounce is invalid, so the
-bounce cannot be delivered. This is probably the most common case, but there
-are also other conditions that cause freezing, and frozen messages are not
-always bounce messages.
-.code
-ignore_bounce_errors_after = 2d
-timeout_frozen_after = 7d
-.endd
-The first of these options specifies that failing bounce messages are to be
-discarded after 2 days in the queue. The second specifies that any frozen
-message (whether a bounce message or not) is to be timed out (and discarded)
-after a week. In this configuration, the first setting ensures that no failing
-bounce message ever lasts a week.
-
-Exim queues it's messages in a spool directory. If you expect to have
-large queues, you may consider using this option. It splits the spool
-directory into subdirectories to avoid file system degradation from
-many files in a single directory, resulting in better performance.
-Manual manipulation of queued messages becomes more complex (though fortunately
-not often needed).
-.code
-# split_spool_directory = true
-.endd
-
-In an ideal world everybody follows the standards. For non-ASCII
-messages RFC 2047 is a standard, allowing a maximum line length of 76
-characters. Exim adheres that standard and won't process messages which
-violate this standard. (Even ${rfc2047:...} expansions will fail.)
-In particular, the Exim maintainers have had multiple reports of
-problems from Russian administrators of issues until they disable this
-check, because of some popular, yet buggy, mail composition software.
-.code
-# check_rfc2047_length = false
-.endd
-
-If you need to be strictly RFC compliant you may wish to disable the
-8BITMIME advertisement. Use this, if you exchange mails with systems
-that are not 8-bit clean.
-.code
-# accept_8bitmime = false
-.endd
-
-Libraries you use may depend on specific environment settings.  This
-imposes a security risk (e.g. PATH). There are two lists:
-&%keep_environment%& for the variables to import as they are, and
-&%add_environment%& for variables we want to set to a fixed value.
-Note that TZ is handled separately, by the $%timezone%$ runtime
-option and by the TIMEZONE_DEFAULT buildtime option.
-.code
-# keep_environment = ^LDAP
-# add_environment = PATH=/usr/bin::/bin
-.endd
-
-
-.section "ACL configuration" "SECID54"
-.cindex "default" "ACLs"
-.cindex "&ACL;" "default configuration"
-In the default configuration, the ACL section follows the main configuration.
-It starts with the line
-.code
-begin acl
-.endd
-and it contains the definitions of two ACLs, called &'acl_check_rcpt'& and
-&'acl_check_data'&, that were referenced in the settings of &%acl_smtp_rcpt%&
-and &%acl_smtp_data%& above.
-
-.cindex "RCPT" "ACL for"
-The first ACL is used for every RCPT command in an incoming SMTP message. Each
-RCPT command specifies one of the message's recipients. The ACL statements
-are considered in order, until the recipient address is either accepted or
-rejected. The RCPT command is then accepted or rejected, according to the
-result of the ACL processing.
-.code
-acl_check_rcpt:
-.endd
-This line, consisting of a name terminated by a colon, marks the start of the
-ACL, and names it.
-.code
-accept  hosts = :
-.endd
-This ACL statement accepts the recipient if the sending host matches the list.
-But what does that strange list mean? It doesn't actually contain any host
-names or IP addresses. The presence of the colon puts an empty item in the
-list; Exim matches this only if the incoming message did not come from a remote
-host, because in that case, the remote hostname is empty. The colon is
-important. Without it, the list itself is empty, and can never match anything.
-
-What this statement is doing is to accept unconditionally all recipients in
-messages that are submitted by SMTP from local processes using the standard
-input and output (that is, not using TCP/IP). A number of MUAs operate in this
-manner.
-.code
-deny    message       = Restricted characters in address
-        domains       = +local_domains
-        local_parts   = ^[.] : ^.*[@%!/|]
-
-deny    message       = Restricted characters in address
-        domains       = !+local_domains
-        local_parts   = ^[./|] : ^.*[@%!] : ^.*/\\.\\./
-.endd
-These statements are concerned with local parts that contain any of the
-characters &"@"&, &"%"&, &"!"&, &"/"&, &"|"&, or dots in unusual places.
-Although these characters are entirely legal in local parts (in the case of
-&"@"& and leading dots, only if correctly quoted), they do not commonly occur
-in Internet mail addresses.
-
-The first three have in the past been associated with explicitly routed
-addresses (percent is still sometimes used &-- see the &%percent_hack_domains%&
-option). Addresses containing these characters are regularly tried by spammers
-in an attempt to bypass relaying restrictions, and also by open relay testing
-programs. Unless you really need them it is safest to reject these characters
-at this early stage. This configuration is heavy-handed in rejecting these
-characters for all messages it accepts from remote hosts. This is a deliberate
-policy of being as safe as possible.
-
-The first rule above is stricter, and is applied to messages that are addressed
-to one of the local domains handled by this host. This is implemented by the
-first condition, which restricts it to domains that are listed in the
-&'local_domains'& domain list. The &"+"& character is used to indicate a
-reference to a named list. In this configuration, there is just one domain in
-&'local_domains'&, but in general there may be many.
-
-The second condition on the first statement uses two regular expressions to
-block local parts that begin with a dot or contain &"@"&, &"%"&, &"!"&, &"/"&,
-or &"|"&. If you have local accounts that include these characters, you will
-have to modify this rule.
-
-Empty components (two dots in a row) are not valid in RFC 2822, but Exim
-allows them because they have been encountered in practice. (Consider the
-common convention of local parts constructed as
-&"&'first-initial.second-initial.family-name'&"& when applied to someone like
-the author of Exim, who has no second initial.) However, a local part starting
-with a dot or containing &"/../"& can cause trouble if it is used as part of a
-filename (for example, for a mailing list). This is also true for local parts
-that contain slashes. A pipe symbol can also be troublesome if the local part
-is incorporated unthinkingly into a shell command line.
-
-The second rule above applies to all other domains, and is less strict. This
-allows your own users to send outgoing messages to sites that use slashes
-and vertical bars in their local parts. It blocks local parts that begin
-with a dot, slash, or vertical bar, but allows these characters within the
-local part. However, the sequence &"/../"& is barred. The use of &"@"&, &"%"&,
-and &"!"& is blocked, as before. The motivation here is to prevent your users
-(or your users' viruses) from mounting certain kinds of attack on remote sites.
-.code
-accept  local_parts   = postmaster
-        domains       = +local_domains
-.endd
-This statement, which has two conditions, accepts an incoming address if the
-local part is &'postmaster'& and the domain is one of those listed in the
-&'local_domains'& domain list. The &"+"& character is used to indicate a
-reference to a named list. In this configuration, there is just one domain in
-&'local_domains'&, but in general there may be many.
-
-The presence of this statement means that mail to postmaster is never blocked
-by any of the subsequent tests. This can be helpful while sorting out problems
-in cases where the subsequent tests are incorrectly denying access.
-.code
-require verify        = sender
-.endd
-This statement requires the sender address to be verified before any subsequent
-ACL statement can be used. If verification fails, the incoming recipient
-address is refused. Verification consists of trying to route the address, to
-see if a bounce message could be delivered to it. In the case of remote
-addresses, basic verification checks only the domain, but &'callouts'& can be
-used for more verification if required. Section &<<SECTaddressverification>>&
-discusses the details of address verification.
-.code
-accept  hosts         = +relay_from_hosts
-        control       = submission
-.endd
-This statement accepts the address if the message is coming from one of the
-hosts that are defined as being allowed to relay through this host. Recipient
-verification is omitted here, because in many cases the clients are dumb MUAs
-that do not cope well with SMTP error responses. For the same reason, the
-second line specifies &"submission mode"& for messages that are accepted. This
-is described in detail in section &<<SECTsubmodnon>>&; it causes Exim to fix
-messages that are deficient in some way, for example, because they lack a
-&'Date:'& header line. If you are actually relaying out from MTAs, you should
-probably add recipient verification here, and disable submission mode.
-.code
-accept  authenticated = *
-        control       = submission
-.endd
-This statement accepts the address if the client host has authenticated itself.
-Submission mode is again specified, on the grounds that such messages are most
-likely to come from MUAs. The default configuration does not define any
-authenticators, though it does include some nearly complete commented-out
-examples described in &<<SECTdefconfauth>>&. This means that no client can in
-fact authenticate until you complete the authenticator definitions.
-.code
-require message = relay not permitted
-        domains = +local_domains : +relay_to_domains
-.endd
-This statement rejects the address if its domain is neither a local domain nor
-one of the domains for which this host is a relay.
-.code
-require verify = recipient
-.endd
-This statement requires the recipient address to be verified; if verification
-fails, the address is rejected.
-.code
-# deny    message     = rejected because $sender_host_address \
-#                       is in a black list at $dnslist_domain\n\
-#                       $dnslist_text
-#         dnslists    = black.list.example
-#
-# warn    dnslists    = black.list.example
-#         add_header  = X-Warning: $sender_host_address is in \
-#                       a black list at $dnslist_domain
-#         log_message = found in $dnslist_domain
-.endd
-These commented-out lines are examples of how you could configure Exim to check
-sending hosts against a DNS black list. The first statement rejects messages
-from blacklisted hosts, whereas the second just inserts a warning header
-line.
-.code
-# require verify = csa
-.endd
-This commented-out line is an example of how you could turn on client SMTP
-authorization (CSA) checking. Such checks do DNS lookups for special SRV
-records.
-.code
-accept
-.endd
-The final statement in the first ACL unconditionally accepts any recipient
-address that has successfully passed all the previous tests.
-.code
-acl_check_data:
-.endd
-This line marks the start of the second ACL, and names it. Most of the contents
-of this ACL are commented out:
-.code
-# deny    malware   = *
-#         message   = This message contains a virus \
-#                     ($malware_name).
-.endd
-These lines are examples of how to arrange for messages to be scanned for
-viruses when Exim has been compiled with the content-scanning extension, and a
-suitable virus scanner is installed. If the message is found to contain a
-virus, it is rejected with the given custom error message.
-.code
-# warn    spam      = nobody
-#         message   = X-Spam_score: $spam_score\n\
-#                     X-Spam_score_int: $spam_score_int\n\
-#                     X-Spam_bar: $spam_bar\n\
-#                     X-Spam_report: $spam_report
-.endd
-These lines are an example of how to arrange for messages to be scanned by
-SpamAssassin when Exim has been compiled with the content-scanning extension,
-and SpamAssassin has been installed. The SpamAssassin check is run with
-&`nobody`& as its user parameter, and the results are added to the message as a
-series of extra header line. In this case, the message is not rejected,
-whatever the spam score.
-.code
-accept
-.endd
-This final line in the DATA ACL accepts the message unconditionally.
-
-
-.section "Router configuration" "SECID55"
-.cindex "default" "routers"
-.cindex "routers" "default"
-The router configuration comes next in the default configuration, introduced
-by the line
-.code
-begin routers
-.endd
-Routers are the modules in Exim that make decisions about where to send
-messages. An address is passed to each router, in turn, until it is either
-accepted, or failed. This means that the order in which you define the routers
-matters. Each router is fully described in its own chapter later in this
-manual. Here we give only brief overviews.
-.code
-# domain_literal:
-#   driver = ipliteral
-#   domains = !+local_domains
-#   transport = remote_smtp
-.endd
-.cindex "domain literal" "default router"
-This router is commented out because the majority of sites do not want to
-support domain literal addresses (those of the form &'user@[10.9.8.7]'&). If
-you uncomment this router, you also need to uncomment the setting of
-&%allow_domain_literals%& in the main part of the configuration.
-
-Which router is used next depends upon whether or not the ROUTER_SMARTHOST
-macro has been defined, per
-.code
-.ifdef ROUTER_SMARTHOST
-smarthost:
-#...
-.else
-dnslookup:
-#...
-.endif
-.endd
-
-If ROUTER_SMARTHOST has been defined, either at the top of the file or on the
-command-line, then we route all non-local mail to that smarthost; otherwise, we'll
-perform DNS lookups for direct-to-MX lookup.  Any mail which is to a local domain will
-skip these routers because of the &%domains%& option.
-
-.code
-smarthost:
-  driver = manualroute
-  domains = ! +local_domains
-  transport = smarthost_smtp
-  route_data = ROUTER_SMARTHOST
-  ignore_target_hosts = <; 0.0.0.0 ; 127.0.0.0/8 ; ::1
-  no_more
-.endd
-This router only handles mail which is not to any local domains; this is
-specified by the line
-.code
-domains = ! +local_domains
-.endd
-The &%domains%& option lists the domains to which this router applies, but the
-exclamation mark is a negation sign, so the router is used only for domains
-that are not in the domain list called &'local_domains'& (which was defined at
-the start of the configuration). The plus sign before &'local_domains'&
-indicates that it is referring to a named list. Addresses in other domains are
-passed on to the following routers.
-
-The name of the router driver is &(manualroute)& because we are manually
-specifying how mail should be routed onwards, instead of using DNS MX.
-While the name of this router instance is arbitrary, the &%driver%& option must
-be one of the driver modules that is in the Exim binary.
-
-With no pre-conditions other than &%domains%&, all mail for non-local domains
-will be handled by this router, and the &%no_more%& setting will ensure that no
-other routers will be used for messages matching the pre-conditions.  See
-&<<SECTrouprecon>>& for more on how the pre-conditions apply.  For messages which
-are handled by this router, we provide a hostname to deliver to in &%route_data%&
-and the macro supplies the value; the address is then queued for the
-&(smarthost_smtp)& transport.
-
-.code
-dnslookup:
-  driver = dnslookup
-  domains = ! +local_domains
-  transport = remote_smtp
-  ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
-  no_more
-.endd
-The &%domains%& option behaves as per smarthost, above.
-
-The name of the router driver is &(dnslookup)&,
-and is specified by the &%driver%& option. Do not be confused by the fact that
-the name of this router instance is the same as the name of the driver. The
-instance name is arbitrary, but the name set in the &%driver%& option must be
-one of the driver modules that is in the Exim binary.
-
-The &(dnslookup)& router routes addresses by looking up their domains in the
-DNS in order to obtain a list of hosts to which the address is routed. If the
-router succeeds, the address is queued for the &(remote_smtp)& transport, as
-specified by the &%transport%& option. If the router does not find the domain
-in the DNS, no further routers are tried because of the &%no_more%& setting, so
-the address fails and is bounced.
-
-The &%ignore_target_hosts%& option specifies a list of IP addresses that are to
-be entirely ignored. This option is present because a number of cases have been
-encountered where MX records in the DNS point to host names
-whose IP addresses are 0.0.0.0 or are in the 127 subnet (typically 127.0.0.1).
-Completely ignoring these IP addresses causes Exim to fail to route the
-email address, so it bounces. Otherwise, Exim would log a routing problem, and
-continue to try to deliver the message periodically until the address timed
-out.
-.code
-system_aliases:
-  driver = redirect
-  allow_fail
-  allow_defer
-  data = ${lookup{$local_part}lsearch{/etc/aliases}}
-# user = exim
-  file_transport = address_file
-  pipe_transport = address_pipe
-.endd
-Control reaches this and subsequent routers only for addresses in the local
-domains. This router checks to see whether the local part is defined as an
-alias in the &_/etc/aliases_& file, and if so, redirects it according to the
-data that it looks up from that file. If no data is found for the local part,
-the value of the &%data%& option is empty, causing the address to be passed to
-the next router.
-
-&_/etc/aliases_& is a conventional name for the system aliases file that is
-often used. That is why it is referenced by from the default configuration
-file. However, you can change this by setting SYSTEM_ALIASES_FILE in
-&_Local/Makefile_& before building Exim.
-.code
-userforward:
-  driver = redirect
-  check_local_user
-# local_part_suffix = +* : -*
-# local_part_suffix_optional
-  file = $home/.forward
-# allow_filter
-  no_verify
-  no_expn
-  check_ancestor
-  file_transport = address_file
-  pipe_transport = address_pipe
-  reply_transport = address_reply
-.endd
-This is the most complicated router in the default configuration. It is another
-redirection router, but this time it is looking for forwarding data set up by
-individual users. The &%check_local_user%& setting specifies a check that the
-local part of the address is the login name of a local user. If it is not, the
-router is skipped. The two commented options that follow &%check_local_user%&,
-namely:
-.code
-# local_part_suffix = +* : -*
-# local_part_suffix_optional
-.endd
-.vindex "&$local_part_suffix$&"
-show how you can specify the recognition of local part suffixes. If the first
-is uncommented, a suffix beginning with either a plus or a minus sign, followed
-by any sequence of characters, is removed from the local part and placed in the
-variable &$local_part_suffix$&. The second suffix option specifies that the
-presence of a suffix in the local part is optional. When a suffix is present,
-the check for a local login uses the local part with the suffix removed.
-
-When a local user account is found, the file called &_.forward_& in the user's
-home directory is consulted. If it does not exist, or is empty, the router
-declines. Otherwise, the contents of &_.forward_& are interpreted as
-redirection data (see chapter &<<CHAPredirect>>& for more details).
-
-.cindex "Sieve filter" "enabling in default router"
-Traditional &_.forward_& files contain just a list of addresses, pipes, or
-files. Exim supports this by default. However, if &%allow_filter%& is set (it
-is commented out by default), the contents of the file are interpreted as a set
-of Exim or Sieve filtering instructions, provided the file begins with &"#Exim
-filter"& or &"#Sieve filter"&, respectively. User filtering is discussed in the
-separate document entitled &'Exim's interfaces to mail filtering'&.
-
-The &%no_verify%& and &%no_expn%& options mean that this router is skipped when
-verifying addresses, or when running as a consequence of an SMTP EXPN command.
-There are two reasons for doing this:
-
-.olist
-Whether or not a local user has a &_.forward_& file is not really relevant when
-checking an address for validity; it makes sense not to waste resources doing
-unnecessary work.
-.next
-More importantly, when Exim is verifying addresses or handling an EXPN
-command during an SMTP session, it is running as the Exim user, not as root.
-The group is the Exim group, and no additional groups are set up.
-It may therefore not be possible for Exim to read users' &_.forward_& files at
-this time.
-.endlist
-
-The setting of &%check_ancestor%& prevents the router from generating a new
-address that is the same as any previous address that was redirected. (This
-works round a problem concerning a bad interaction between aliasing and
-forwarding &-- see section &<<SECTredlocmai>>&).
-
-The final three option settings specify the transports that are to be used when
-forwarding generates a direct delivery to a file, or to a pipe, or sets up an
-auto-reply, respectively. For example, if a &_.forward_& file contains
-.code
-a.nother@elsewhere.example, /home/spqr/archive
-.endd
-the delivery to &_/home/spqr/archive_& is done by running the &%address_file%&
-transport.
-.code
-localuser:
-  driver = accept
-  check_local_user
-# local_part_suffix = +* : -*
-# local_part_suffix_optional
-  transport = local_delivery
-.endd
-The final router sets up delivery into local mailboxes, provided that the local
-part is the name of a local login, by accepting the address and assigning it to
-the &(local_delivery)& transport. Otherwise, we have reached the end of the
-routers, so the address is bounced. The commented suffix settings fulfil the
-same purpose as they do for the &(userforward)& router.
-
-
-.section "Transport configuration" "SECID56"
-.cindex "default" "transports"
-.cindex "transports" "default"
-Transports define mechanisms for actually delivering messages. They operate
-only when referenced from routers, so the order in which they are defined does
-not matter. The transports section of the configuration starts with
-.code
-begin transports
-.endd
-Two remote transports and four local transports are defined.
-.code
-remote_smtp:
-  driver = smtp
-  message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
-.ifdef _HAVE_PRDR
-  hosts_try_prdr = *
-.endif
-.endd
-This transport is used for delivering messages over SMTP connections.
-The list of remote hosts comes from the router.
-The &%message_size_limit%& usage is a hack to avoid sending on messages
-with over-long lines.
-
-The &%hosts_try_prdr%& option enables an efficiency SMTP option.  It is
-negotiated between client and server and not expected to cause problems
-but can be disabled if needed.  The built-in macro _HAVE_PRDR guards the
-use of the &%hosts_try_prdr%& configuration option.
-
-The other remote transport is used when delivering to a specific smarthost
-with whom there must be some kind of existing relationship, instead of the
-usual federated system.
-
-.code
-smarthost_smtp:
-  driver = smtp
-  message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
-  multi_domain
-  #
-.ifdef _HAVE_TLS
-  # Comment out any of these which you have to, then file a Support
-  # request with your smarthost provider to get things fixed:
-  hosts_require_tls = *
-  tls_verify_hosts = *
-  # As long as tls_verify_hosts is enabled, this won't matter, but if you
-  # have to comment it out then this will at least log whether you succeed
-  # or not:
-  tls_try_verify_hosts = *
-  #
-  # The SNI name should match the name which we'll expect to verify;
-  # many mail systems don't use SNI and this doesn't matter, but if it does,
-  # we need to send a name which the remote site will recognize.
-  # This _should_ be the name which the smarthost operators specified as
-  # the hostname for sending your mail to.
-  tls_sni = ROUTER_SMARTHOST
-  #
-.ifdef _HAVE_OPENSSL
-  tls_require_ciphers = HIGH:!aNULL:@STRENGTH
-.endif
-.ifdef _HAVE_GNUTLS
-  tls_require_ciphers = SECURE192:-VERS-SSL3.0:-VERS-TLS1.0:-VERS-TLS1.1
-.endif
-.endif
-.ifdef _HAVE_PRDR
-  hosts_try_prdr = *
-.endif
-.endd
-After the same &%message_size_limit%& hack, we then specify that this Transport
-can handle messages to multiple domains in one run.  The assumption here is
-that you're routing all non-local mail to the same place and that place is
-happy to take all messages from you as quickly as possible.
-All other options depend upon built-in macros; if Exim was built without TLS support
-then no other options are defined.
-If TLS is available, then we configure "stronger than default" TLS ciphersuites
-and versions using the &%tls_require_ciphers%& option, where the value to be
-used depends upon the library providing TLS.
-Beyond that, the options adopt the stance that you should have TLS support available
-from your smarthost on today's Internet, so we turn on requiring TLS for the
-mail to be delivered, and requiring that the certificate be valid, and match
-the expected hostname.  The &%tls_sni%& option can be used by service providers
-to select an appropriate certificate to present to you and here we re-use the
-ROUTER_SMARTHOST macro, because that is unaffected by CNAMEs present in DNS.
-You want to specify the hostname which you'll expect to validate for, and that
-should not be subject to insecure tampering via DNS results.
-
-For the &%hosts_try_prdr%& option see the previous transport.
-
-All other options are defaulted.
-.code
-local_delivery:
-  driver = appendfile
-  file = /var/mail/$local_part_verified
-  delivery_date_add
-  envelope_to_add
-  return_path_add
-# group = mail
-# mode = 0660
-.endd
-This &(appendfile)& transport is used for local delivery to user mailboxes in
-traditional BSD mailbox format.
-
-.new
-We prefer to avoid using &$local_part$& directly to define the mailbox filename,
-as it is provided by a potential bad actor.
-Instead we use &$local_part_verified$&,
-the result of looking up &$local_part$& in the user database
-(done by using &%check_local_user%& in the the router).
-.wen
-
-By default &(appendfile)& runs under the uid and gid of the
-local user, which requires the sticky bit to be set on the &_/var/mail_&
-directory. Some systems use the alternative approach of running mail deliveries
-under a particular group instead of using the sticky bit. The commented options
-show how this can be done.
-
-Exim adds three headers to the message as it delivers it: &'Delivery-date:'&,
-&'Envelope-to:'& and &'Return-path:'&. This action is requested by the three
-similarly-named options above.
-.code
-address_pipe:
-  driver = pipe
-  return_output
-.endd
-This transport is used for handling deliveries to pipes that are generated by
-redirection (aliasing or users' &_.forward_& files). The &%return_output%&
-option specifies that any output on stdout or stderr generated by the pipe is to
-be returned to the sender.
-.code
-address_file:
-  driver = appendfile
-  delivery_date_add
-  envelope_to_add
-  return_path_add
-.endd
-This transport is used for handling deliveries to files that are generated by
-redirection. The name of the file is not specified in this instance of
-&(appendfile)&, because it comes from the &(redirect)& router.
-.code
-address_reply:
-  driver = autoreply
-.endd
-This transport is used for handling automatic replies generated by users'
-filter files.
-
-
-
-.section "Default retry rule" "SECID57"
-.cindex "retry" "default rule"
-.cindex "default" "retry rule"
-The retry section of the configuration file contains rules which affect the way
-Exim retries deliveries that cannot be completed at the first attempt. It is
-introduced by the line
-.code
-begin retry
-.endd
-In the default configuration, there is just one rule, which applies to all
-errors:
-.code
-*   *   F,2h,15m; G,16h,1h,1.5; F,4d,6h
-.endd
-This causes any temporarily failing address to be retried every 15 minutes for
-2 hours, then at intervals starting at one hour and increasing by a factor of
-1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address
-is not delivered after 4 days of temporary failure, it is bounced. The time is
-measured from first failure, not from the time the message was received.
-
-If the retry section is removed from the configuration, or is empty (that is,
-if no retry rules are defined), Exim will not retry deliveries. This turns
-temporary errors into permanent errors.
-
-
-.section "Rewriting configuration" "SECID58"
-The rewriting section of the configuration, introduced by
-.code
-begin rewrite
-.endd
-contains rules for rewriting addresses in messages as they arrive. There are no
-rewriting rules in the default configuration file.
-
-
-
-.section "Authenticators configuration" "SECTdefconfauth"
-.cindex "AUTH" "configuration"
-The authenticators section of the configuration, introduced by
-.code
-begin authenticators
-.endd
-defines mechanisms for the use of the SMTP AUTH command. The default
-configuration file contains two commented-out example authenticators
-which support plaintext username/password authentication using the
-standard PLAIN mechanism and the traditional but non-standard LOGIN
-mechanism, with Exim acting as the server. PLAIN and LOGIN are enough
-to support most MUA software.
-
-The example PLAIN authenticator looks like this:
-.code
-#PLAIN:
-#  driver                  = plaintext
-#  server_set_id           = $auth2
-#  server_prompts          = :
-#  server_condition        = Authentication is not yet configured
-#  server_advertise_condition = ${if def:tls_in_cipher }
-.endd
-And the example LOGIN authenticator looks like this:
-.code
-#LOGIN:
-#  driver                  = plaintext
-#  server_set_id           = $auth1
-#  server_prompts          = <| Username: | Password:
-#  server_condition        = Authentication is not yet configured
-#  server_advertise_condition = ${if def:tls_in_cipher }
-.endd
-
-The &%server_set_id%& option makes Exim remember the authenticated username
-in &$authenticated_id$&, which can be used later in ACLs or routers. The
-&%server_prompts%& option configures the &(plaintext)& authenticator so
-that it implements the details of the specific authentication mechanism,
-i.e. PLAIN or LOGIN. The &%server_advertise_condition%& setting controls
-when Exim offers authentication to clients; in the examples, this is only
-when TLS or SSL has been started, so to enable the authenticators you also
-need to add support for TLS as described in section &<<SECTdefconfmain>>&.
-
-The &%server_condition%& setting defines how to verify that the username and
-password are correct. In the examples it just produces an error message.
-To make the authenticators work, you can use a string expansion
-expression like one of the examples in chapter &<<CHAPplaintext>>&.
-
-Beware that the sequence of the parameters to PLAIN and LOGIN differ; the
-usercode and password are in different positions.
-Chapter &<<CHAPplaintext>>& covers both.
-
-.ecindex IIDconfiwal
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "Regular expressions" "CHAPregexp"
-
-.cindex "regular expressions" "library"
-.cindex "PCRE"
-Exim supports the use of regular expressions in many of its options. It
-uses the PCRE regular expression library; this provides regular expression
-matching that is compatible with Perl 5. The syntax and semantics of
-regular expressions is discussed in
-online Perl manpages, in
-many Perl reference books, and also in
-Jeffrey Friedl's &'Mastering Regular Expressions'&, which is published by
-O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)).
-. --- the http: URL here redirects to another page with the ISBN in the URL
-. --- where trying to use https: just redirects back to http:, so sticking
-. --- to the old URL for now.  2018-09-07.
-
-The documentation for the syntax and semantics of the regular expressions that
-are supported by PCRE is included in the PCRE distribution, and no further
-description is included here. The PCRE functions are called from Exim using
-the default option settings (that is, with no PCRE options set), except that
-the PCRE_CASELESS option is set when the matching is required to be
-case-insensitive.
-
-In most cases, when a regular expression is required in an Exim configuration,
-it has to start with a circumflex, in order to distinguish it from plain text
-or an &"ends with"& wildcard. In this example of a configuration setting, the
-second item in the colon-separated list is a regular expression.
-.code
-domains = a.b.c : ^\\d{3} : *.y.z : ...
-.endd
-The doubling of the backslash is required because of string expansion that
-precedes interpretation &-- see section &<<SECTlittext>>& for more discussion
-of this issue, and a way of avoiding the need for doubling backslashes. The
-regular expression that is eventually used in this example contains just one
-backslash. The circumflex is included in the regular expression, and has the
-normal effect of &"anchoring"& it to the start of the string that is being
-matched.
-
-There are, however, two cases where a circumflex is not required for the
-recognition of a regular expression: these are the &%match%& condition in a
-string expansion, and the &%matches%& condition in an Exim filter file. In
-these cases, the relevant string is always treated as a regular expression; if
-it does not start with a circumflex, the expression is not anchored, and can
-match anywhere in the subject string.
-
-In all cases, if you want a regular expression to match at the end of a string,
-you must code the $ metacharacter to indicate this. For example:
-.code
-domains = ^\\d{3}\\.example
-.endd
-matches the domain &'123.example'&, but it also matches &'123.example.com'&.
-You need to use:
-.code
-domains = ^\\d{3}\\.example\$
-.endd
-if you want &'example'& to be the top-level domain. The backslash before the
-$ is needed because string expansion also interprets dollar characters.
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "File and database lookups" "CHAPfdlookup"
-.scindex IIDfidalo1 "file" "lookups"
-.scindex IIDfidalo2 "database" "lookups"
-.cindex "lookup" "description of"
-Exim can be configured to look up data in files or databases as it processes
-messages. Two different kinds of syntax are used:
-
-.olist
-A string that is to be expanded may contain explicit lookup requests. These
-cause parts of the string to be replaced by data that is obtained from the
-lookup. Lookups of this type are conditional expansion items. Different results
-can be defined for the cases of lookup success and failure. See chapter
-&<<CHAPexpand>>&, where string expansions are described in detail.
-The key for the lookup is specified as part of the string expansion.
-.next
-Lists of domains, hosts, and email addresses can contain lookup requests as a
-way of avoiding excessively long linear lists. In this case, the data that is
-returned by the lookup is often (but not always) discarded; whether the lookup
-succeeds or fails is what really counts. These kinds of list are described in
-chapter &<<CHAPdomhosaddlists>>&.
-The key for the lookup is given by the context in which the list is expanded.
-.endlist
-
-String expansions, lists, and lookups interact with each other in such a way
-that there is no order in which to describe any one of them that does not
-involve references to the others. Each of these three chapters makes more sense
-if you have read the other two first. If you are reading this for the first
-time, be aware that some of it will make a lot more sense after you have read
-chapters &<<CHAPdomhosaddlists>>& and &<<CHAPexpand>>&.
-
-.section "Examples of different lookup syntax" "SECID60"
-It is easy to confuse the two different kinds of lookup, especially as the
-lists that may contain the second kind are always expanded before being
-processed as lists. Therefore, they may also contain lookups of the first kind.
-Be careful to distinguish between the following two examples:
-.code
-domains = ${lookup{$sender_host_address}lsearch{/some/file}}
-domains = lsearch;/some/file
-.endd
-The first uses a string expansion, the result of which must be a domain list.
-No strings have been specified for a successful or a failing lookup; the
-defaults in this case are the looked-up data and an empty string, respectively.
-The expansion takes place before the string is processed as a list, and the
-file that is searched could contain lines like this:
-.code
-192.168.3.4: domain1:domain2:...
-192.168.1.9: domain3:domain4:...
-.endd
-When the lookup succeeds, the result of the expansion is a list of domains (and
-possibly other types of item that are allowed in domain lists).
-
-In the second example, the lookup is a single item in a domain list. It causes
-Exim to use a lookup to see if the domain that is being processed can be found
-in the file. The file could contains lines like this:
-.code
-domain1:
-domain2:
-.endd
-Any data that follows the keys is not relevant when checking that the domain
-matches the list item.
-
-It is possible, though no doubt confusing, to use both kinds of lookup at once.
-Consider a file containing lines like this:
-.code
-192.168.5.6: lsearch;/another/file
-.endd
-If the value of &$sender_host_address$& is 192.168.5.6, expansion of the
-first &%domains%& setting above generates the second setting, which therefore
-causes a second lookup to occur.
-
-The rest of this chapter describes the different lookup types that are
-available. Any of them can be used in any part of the configuration where a
-lookup is permitted.
-
-
-.section "Lookup types" "SECID61"
-.cindex "lookup" "types of"
-.cindex "single-key lookup" "definition of"
-Two different types of data lookup are implemented:
-
-.ilist
-The &'single-key'& type requires the specification of a file in which to look,
-and a single key to search for. The key must be a non-empty string for the
-lookup to succeed. The lookup type determines how the file is searched.
-.new
-.cindex "tainted data" "single-key lookups"
-The file string may not be tainted
-.wen
-.next
-.cindex "query-style lookup" "definition of"
-The &'query-style'& type accepts a generalized database query. No particular
-key value is assumed by Exim for query-style lookups. You can use whichever
-Exim variables you need to construct the database query.
-.endlist
-
-The code for each lookup type is in a separate source file that is included in
-the binary of Exim only if the corresponding compile-time option is set. The
-default settings in &_src/EDITME_& are:
-.code
-LOOKUP_DBM=yes
-LOOKUP_LSEARCH=yes
-.endd
-which means that only linear searching and DBM lookups are included by default.
-For some types of lookup (e.g. SQL databases), you need to install appropriate
-libraries and header files before building Exim.
-
-
-
-
-.section "Single-key lookup types" "SECTsinglekeylookups"
-.cindex "lookup" "single-key types"
-.cindex "single-key lookup" "list of types"
-The following single-key lookup types are implemented:
-
-.ilist
-.cindex "cdb" "description of"
-.cindex "lookup" "cdb"
-.cindex "binary zero" "in lookup key"
-&(cdb)&: The given file is searched as a Constant DataBase file, using the key
-string without a terminating binary zero. The cdb format is designed for
-indexed files that are read frequently and never updated, except by total
-re-creation. As such, it is particularly suitable for large files containing
-aliases or other indexed data referenced by an MTA. Information about cdb and
-tools for building the files can be found in several places:
-.display
-&url(https://cr.yp.to/cdb.html)
-&url(https://www.corpit.ru/mjt/tinycdb.html)
-&url(https://packages.debian.org/stable/utils/freecdb)
-&url(https://github.com/philpennock/cdbtools) (in Go)
-.endd
-A cdb distribution is not needed in order to build Exim with cdb support,
-because the code for reading cdb files is included directly in Exim itself.
-However, no means of building or testing cdb files is provided with Exim, so
-you need to obtain a cdb distribution in order to do this.
-.next
-.cindex "DBM" "lookup type"
-.cindex "lookup" "dbm"
-.cindex "binary zero" "in lookup key"
-&(dbm)&: Calls to DBM library functions are used to extract data from the given
-DBM file by looking up the record with the given key. A terminating binary
-zero is included in the key that is passed to the DBM library. See section
-&<<SECTdb>>& for a discussion of DBM libraries.
-
-.cindex "Berkeley DB library" "file format"
-For all versions of Berkeley DB, Exim uses the DB_HASH style of database
-when building DBM files using the &%exim_dbmbuild%& utility. However, when
-using Berkeley DB versions 3 or 4, it opens existing databases for reading with
-the DB_UNKNOWN option. This enables it to handle any of the types of database
-that the library supports, and can be useful for accessing DBM files created by
-other applications. (For earlier DB versions, DB_HASH is always used.)
-.next
-.cindex "lookup" "dbmjz"
-.cindex "lookup" "dbm &-- embedded NULs"
-.cindex "sasldb2"
-.cindex "dbmjz lookup type"
-&(dbmjz)&: This is the same as &(dbm)&, except that the lookup key is
-interpreted as an Exim list; the elements of the list are joined together with
-ASCII NUL characters to form the lookup key.  An example usage would be to
-authenticate incoming SMTP calls using the passwords from Cyrus SASL's
-&_/etc/sasldb2_& file with the &(gsasl)& authenticator or Exim's own
-&(cram_md5)& authenticator.
-.next
-.cindex "lookup" "dbmnz"
-.cindex "lookup" "dbm &-- terminating zero"
-.cindex "binary zero" "in lookup key"
-.cindex "Courier"
-.cindex "&_/etc/userdbshadow.dat_&"
-.cindex "dbmnz lookup type"
-&(dbmnz)&: This is the same as &(dbm)&, except that a terminating binary zero
-is not included in the key that is passed to the DBM library. You may need this
-if you want to look up data in files that are created by or shared with some
-other application that does not use terminating zeros. For example, you need to
-use &(dbmnz)& rather than &(dbm)& if you want to authenticate incoming SMTP
-calls using the passwords from Courier's &_/etc/userdbshadow.dat_& file. Exim's
-utility program for creating DBM files (&'exim_dbmbuild'&) includes the zeros
-by default, but has an option to omit them (see section &<<SECTdbmbuild>>&).
-.next
-.cindex "lookup" "dsearch"
-.cindex "dsearch lookup type"
-&(dsearch)&: The given file must be an
-.new
-absolute
-.wen
-directory path; this is searched for an entry
-whose name is the key by calling the &[lstat()]& function.
-The key may not
-contain any forward slash characters.
-If &[lstat()]& succeeds then so does the lookup.
-.new
-.cindex "tainted data" "dsearch result"
-The result is regarded as untainted.
-
-Options for the lookup can be given by appending them after the word "dsearch",
-separated by a comma.  Options, if present, are a comma-separated list having
-each element starting with a tag name and an equals.
-
-Two options are supported, for the return value and for filtering match
-candidates.
-The "ret" option requests an alternate result value of
-the entire path for the entry. Example:
-.code
-${lookup {passwd} dsearch,ret=full {/etc}}
-.endd
-The default result is just the requested entry.
-The "filter" option requests that only directory entries of a given type
-are matched. The match value is one of "file", "dir" or "subdir" (the latter
-not matching "." or ".."). Example:
-.code
-${lookup {passwd} dsearch,filter=file {/etc}}
-.endd
-The default matching is for any entry type, including directories
-and symlinks.
-.wen
-
-An example of how this
-lookup can be used to support virtual domains is given in section
-&<<SECTvirtualdomains>>&.
-.next
-.cindex "lookup" "iplsearch"
-.cindex "iplsearch lookup type"
-&(iplsearch)&: The given file is a text file containing keys and data. A key is
-terminated by a colon or white space or the end of the line. The keys in the
-file must be IP addresses, or IP addresses with CIDR masks. Keys that involve
-IPv6 addresses must be enclosed in quotes to prevent the first internal colon
-being interpreted as a key terminator. For example:
-.code
-1.2.3.4:           data for 1.2.3.4
-192.168.0.0/16:    data for 192.168.0.0/16
-"abcd::cdab":      data for abcd::cdab
-"abcd:abcd::/32"   data for abcd:abcd::/32
-.endd
-The key for an &(iplsearch)& lookup must be an IP address (without a mask). The
-file is searched linearly, using the CIDR masks where present, until a matching
-key is found. The first key that matches is used; there is no attempt to find a
-&"best"& match. Apart from the way the keys are matched, the processing for
-&(iplsearch)& is the same as for &(lsearch)&.
-
-&*Warning 1*&: Unlike most other single-key lookup types, a file of data for
-&(iplsearch)& can &'not'& be turned into a DBM or cdb file, because those
-lookup types support only literal keys.
-
-&*Warning 2*&: In a host list, you must always use &(net-iplsearch)& so that
-the implicit key is the host's IP address rather than its name (see section
-&<<SECThoslispatsikey>>&).
-
-&*Warning 3*&: Do not use an IPv4-mapped IPv6 address for a key; use the
-IPv4, in dotted-quad form. (Exim converts IPv4-mapped IPv6 addresses to this
-notation before executing the lookup.)
-.next
-.cindex lookup json
-.cindex json "lookup type"
-.cindex JSON expansions
-&(json)&: The given file is a text file with a JSON structure.
-An element of the structure is extracted, defined by the search key.
-The key is a list of subelement selectors
-(colon-separated by default but changeable in the usual way)
-which are applied in turn to select smaller and smaller portions
-of the JSON structure.
-If a selector is numeric, it must apply to a JSON array; the (zero-based)
-nunbered array element is selected.
-Otherwise it must apply to a JSON object; the named element is selected.
-The final resulting element can be a simple JSON type or a JSON object
-or array; for the latter two a string-representation os the JSON
-is returned.
-For elements of type string, the returned value is de-quoted.
-.next
-.cindex "linear search"
-.cindex "lookup" "lsearch"
-.cindex "lsearch lookup type"
-.cindex "case sensitivity" "in lsearch lookup"
-&(lsearch)&: The given file is a text file that is searched linearly for a
-line beginning with the search key, terminated by a colon or white space or the
-end of the line. The search is case-insensitive; that is, upper and lower case
-letters are treated as the same. The first occurrence of the key that is found
-in the file is used.
-
-White space between the key and the colon is permitted. The remainder of the
-line, with leading and trailing white space removed, is the data. This can be
-continued onto subsequent lines by starting them with any amount of white
-space, but only a single space character is included in the data at such a
-junction. If the data begins with a colon, the key must be terminated by a
-colon, for example:
-.code
-baduser:  :fail:
-.endd
-Empty lines and lines beginning with # are ignored, even if they occur in the
-middle of an item. This is the traditional textual format of alias files. Note
-that the keys in an &(lsearch)& file are literal strings. There is no
-wildcarding of any kind.
-
-.cindex "lookup" "lsearch &-- colons in keys"
-.cindex "white space" "in lsearch key"
-In most &(lsearch)& files, keys are not required to contain colons or #
-characters, or white space. However, if you need this feature, it is available.
-If a key begins with a doublequote character, it is terminated only by a
-matching quote (or end of line), and the normal escaping rules apply to its
-contents (see section &<<SECTstrings>>&). An optional colon is permitted after
-quoted keys (exactly as for unquoted keys). There is no special handling of
-quotes for the data part of an &(lsearch)& line.
-
-.next
-.cindex "NIS lookup type"
-.cindex "lookup" "NIS"
-.cindex "binary zero" "in lookup key"
-&(nis)&: The given file is the name of a NIS map, and a NIS lookup is done with
-the given key, without a terminating binary zero. There is a variant called
-&(nis0)& which does include the terminating binary zero in the key. This is
-reportedly needed for Sun-style alias files. Exim does not recognize NIS
-aliases; the full map names must be used.
-
-.next
-.cindex "wildlsearch lookup type"
-.cindex "lookup" "wildlsearch"
-.cindex "nwildlsearch lookup type"
-.cindex "lookup" "nwildlsearch"
-&(wildlsearch)& or &(nwildlsearch)&: These search a file linearly, like
-&(lsearch)&, but instead of being interpreted as a literal string, each key in
-the file may be wildcarded. The difference between these two lookup types is
-that for &(wildlsearch)&, each key in the file is string-expanded before being
-used, whereas for &(nwildlsearch)&, no expansion takes place.
-
-.cindex "case sensitivity" "in (n)wildlsearch lookup"
-Like &(lsearch)&, the testing is done case-insensitively. However, keys in the
-file that are regular expressions can be made case-sensitive by the use of
-&`(-i)`& within the pattern. The following forms of wildcard are recognized:
-
-. ==== As this is a nested list, any displays it contains must be indented
-. ==== as otherwise they are too far to the left.
-
-.olist
-The string may begin with an asterisk to mean &"ends with"&. For example:
-.code
-    *.a.b.c       data for anything.a.b.c
-    *fish         data for anythingfish
-.endd
-.next
-The string may begin with a circumflex to indicate a regular expression. For
-example, for &(wildlsearch)&:
-.code
-    ^\N\d+\.a\.b\N    data for <digits>.a.b
-.endd
-Note the use of &`\N`& to disable expansion of the contents of the regular
-expression. If you are using &(nwildlsearch)&, where the keys are not
-string-expanded, the equivalent entry is:
-.code
-    ^\d+\.a\.b        data for <digits>.a.b
-.endd
-The case-insensitive flag is set at the start of compiling the regular
-expression, but it can be turned off by using &`(-i)`& at an appropriate point.
-For example, to make the entire pattern case-sensitive:
-.code
-    ^(?-i)\d+\.a\.b        data for <digits>.a.b
-.endd
-
-If the regular expression contains white space or colon characters, you must
-either quote it (see &(lsearch)& above), or represent these characters in other
-ways. For example, &`\s`& can be used for white space and &`\x3A`& for a
-colon. This may be easier than quoting, because if you quote, you have to
-escape all the backslashes inside the quotes.
-
-&*Note*&: It is not possible to capture substrings in a regular expression
-match for later use, because the results of all lookups are cached. If a lookup
-is repeated, the result is taken from the cache, and no actual pattern matching
-takes place. The values of all the numeric variables are unset after a
-&((n)wildlsearch)& match.
-
-.next
-Although I cannot see it being of much use, the general matching function that
-is used to implement &((n)wildlsearch)& means that the string may begin with a
-lookup name terminated by a semicolon, and followed by lookup data. For
-example:
-.code
-    cdb;/some/file  data for keys that match the file
-.endd
-The data that is obtained from the nested lookup is discarded.
-.endlist olist
-
-Keys that do not match any of these patterns are interpreted literally. The
-continuation rules for the data are the same as for &(lsearch)&, and keys may
-be followed by optional colons.
-
-&*Warning*&: Unlike most other single-key lookup types, a file of data for
-&((n)wildlsearch)& can &'not'& be turned into a DBM or cdb file, because those
-lookup types support only literal keys.
-
-.next
-.cindex "lookup" "spf"
-If Exim is built with SPF support, manual lookups can be done
-(as opposed to the standard ACL condition method.
-For details see section &<<SECSPF>>&.
-.endlist ilist
-
-
-.section "Query-style lookup types" "SECTquerystylelookups"
-.cindex "lookup" "query-style types"
-.cindex "query-style lookup" "list of types"
-The supported query-style lookup types are listed below. Further details about
-many of them are given in later sections.
-
-.ilist
-.cindex "DNS" "as a lookup type"
-.cindex "lookup" "DNS"
-&(dnsdb)&: This does a DNS search for one or more records whose domain names
-are given in the supplied query. The resulting data is the contents of the
-records. See section &<<SECTdnsdb>>&.
-.next
-.cindex "InterBase lookup type"
-.cindex "lookup" "InterBase"
-&(ibase)&: This does a lookup in an InterBase database.
-.next
-.cindex "LDAP" "lookup type"
-.cindex "lookup" "LDAP"
-&(ldap)&: This does an LDAP lookup using a query in the form of a URL, and
-returns attributes from a single entry. There is a variant called &(ldapm)&
-that permits values from multiple entries to be returned. A third variant
-called &(ldapdn)& returns the Distinguished Name of a single entry instead of
-any attribute values. See section &<<SECTldap>>&.
-.next
-.cindex "MySQL" "lookup type"
-.cindex "lookup" "MySQL"
-&(mysql)&: The format of the query is an SQL statement that is passed to a
-MySQL database. See section &<<SECTsql>>&.
-.next
-.cindex "NIS+ lookup type"
-.cindex "lookup" "NIS+"
-&(nisplus)&: This does a NIS+ lookup using a query that can specify the name of
-the field to be returned. See section &<<SECTnisplus>>&.
-.next
-.cindex "Oracle" "lookup type"
-.cindex "lookup" "Oracle"
-&(oracle)&: The format of the query is an SQL statement that is passed to an
-Oracle database. See section &<<SECTsql>>&.
-.next
-.cindex "lookup" "passwd"
-.cindex "passwd lookup type"
-.cindex "&_/etc/passwd_&"
-&(passwd)& is a query-style lookup with queries that are just user names. The
-lookup calls &[getpwnam()]& to interrogate the system password data, and on
-success, the result string is the same as you would get from an &(lsearch)&
-lookup on a traditional &_/etc/passwd file_&, though with &`*`& for the
-password value. For example:
-.code
-*:42:42:King Rat:/home/kr:/bin/bash
-.endd
-.next
-.cindex "PostgreSQL lookup type"
-.cindex "lookup" "PostgreSQL"
-&(pgsql)&: The format of the query is an SQL statement that is passed to a
-PostgreSQL database. See section &<<SECTsql>>&.
-
-.next
-.cindex "Redis lookup type"
-.cindex lookup Redis
-&(redis)&: The format of the query is either a simple get or simple set,
-passed to a Redis database. See section &<<SECTsql>>&.
-
-.next
-.cindex "sqlite lookup type"
-.cindex "lookup" "sqlite"
-&(sqlite)&: The format of the query is
-new
-an optional filename
-.wen
-followed by an SQL statement
-that is passed to an SQLite database. See section &<<SECTsqlite>>&.
-
-.next
-&(testdb)&: This is a lookup type that is used for testing Exim. It is
-not likely to be useful in normal operation.
-.next
-.cindex "whoson lookup type"
-.cindex "lookup" "whoson"
-. --- still http:-only, 2018-09-07
-&(whoson)&: &'Whoson'& (&url(http://whoson.sourceforge.net)) is a protocol that
-allows a server to check whether a particular (dynamically allocated) IP
-address is currently allocated to a known (trusted) user and, optionally, to
-obtain the identity of the said user. For SMTP servers, &'Whoson'& was popular
-at one time for &"POP before SMTP"& authentication, but that approach has been
-superseded by SMTP authentication. In Exim, &'Whoson'& can be used to implement
-&"POP before SMTP"& checking using ACL statements such as
-.code
-require condition = \
-  ${lookup whoson {$sender_host_address}{yes}{no}}
-.endd
-The query consists of a single IP address. The value returned is the name of
-the authenticated user, which is stored in the variable &$value$&. However, in
-this example, the data in &$value$& is not used; the result of the lookup is
-one of the fixed strings &"yes"& or &"no"&.
-.endlist
-
-
-
-.section "Temporary errors in lookups" "SECID63"
-.cindex "lookup" "temporary error in"
-Lookup functions can return temporary error codes if the lookup cannot be
-completed. For example, an SQL or LDAP database might be unavailable. For this
-reason, it is not advisable to use a lookup that might do this for critical
-options such as a list of local domains.
-
-When a lookup cannot be completed in a router or transport, delivery
-of the message (to the relevant address) is deferred, as for any other
-temporary error. In other circumstances Exim may assume the lookup has failed,
-or may give up altogether.
-
-
-
-.section "Default values in single-key lookups" "SECTdefaultvaluelookups"
-.cindex "wildcard lookups"
-.cindex "lookup" "default values"
-.cindex "lookup" "wildcard"
-.cindex "lookup" "* added to type"
-.cindex "default" "in single-key lookups"
-In this context, a &"default value"& is a value specified by the administrator
-that is to be used if a lookup fails.
-
-&*Note:*& This section applies only to single-key lookups. For query-style
-lookups, the facilities of the query language must be used. An attempt to
-specify a default for a query-style lookup provokes an error.
-
-If &"*"& is added to a single-key lookup type (for example, &%lsearch*%&)
-and the initial lookup fails, the key &"*"& is looked up in the file to
-provide a default value. See also the section on partial matching below.
-
-.cindex "*@ with single-key lookup"
-.cindex "lookup" "*@ added to type"
-.cindex "alias file" "per-domain default"
-Alternatively, if &"*@"& is added to a single-key lookup type (for example
-&%dbm*@%&) then, if the initial lookup fails and the key contains an @
-character, a second lookup is done with everything before the last @ replaced
-by *. This makes it possible to provide per-domain defaults in alias files
-that include the domains in the keys. If the second lookup fails (or doesn't
-take place because there is no @ in the key), &"*"& is looked up.
-For example, a &(redirect)& router might contain:
-.code
-data = ${lookup{$local_part@$domain}lsearch*@{/etc/mix-aliases}}
-.endd
-Suppose the address that is being processed is &'jane@eyre.example'&. Exim
-looks up these keys, in this order:
-.code
-jane@eyre.example
-*@eyre.example
-*
-.endd
-The data is taken from whichever key it finds first. &*Note*&: In an
-&(lsearch)& file, this does not mean the first of these keys in the file. A
-complete scan is done for each key, and only if it is not found at all does
-Exim move on to try the next key.
-
-
-
-.section "Partial matching in single-key lookups" "SECTpartiallookup"
-.cindex "partial matching"
-.cindex "wildcard lookups"
-.cindex "lookup" "partial matching"
-.cindex "lookup" "wildcard"
-.cindex "asterisk" "in search type"
-The normal operation of a single-key lookup is to search the file for an exact
-match with the given key. However, in a number of situations where domains are
-being looked up, it is useful to be able to do partial matching. In this case,
-information in the file that has a key starting with &"*."& is matched by any
-domain that ends with the components that follow the full stop. For example, if
-a key in a DBM file is
-.code
-*.dates.fict.example
-.endd
-then when partial matching is enabled this is matched by (amongst others)
-&'2001.dates.fict.example'& and &'1984.dates.fict.example'&. It is also matched
-by &'dates.fict.example'&, if that does not appear as a separate key in the
-file.
-
-&*Note*&: Partial matching is not available for query-style lookups. It is
-also not available for any lookup items in address lists (see section
-&<<SECTaddresslist>>&).
-
-Partial matching is implemented by doing a series of separate lookups using
-keys constructed by modifying the original subject key. This means that it can
-be used with any of the single-key lookup types, provided that
-partial matching keys
-beginning with a special prefix (default &"*."&) are included in the data file.
-Keys in the file that do not begin with the prefix are matched only by
-unmodified subject keys when partial matching is in use.
-
-Partial matching is requested by adding the string &"partial-"& to the front of
-the name of a single-key lookup type, for example, &%partial-dbm%&. When this
-is done, the subject key is first looked up unmodified; if that fails, &"*."&
-is added at the start of the subject key, and it is looked up again. If that
-fails, further lookups are tried with dot-separated components removed from the
-start of the subject key, one-by-one, and &"*."& added on the front of what
-remains.
-
-A minimum number of two non-* components are required. This can be adjusted
-by including a number before the hyphen in the search type. For example,
-&%partial3-lsearch%& specifies a minimum of three non-* components in the
-modified keys. Omitting the number is equivalent to &"partial2-"&. If the
-subject key is &'2250.dates.fict.example'& then the following keys are looked
-up when the minimum number of non-* components is two:
-.code
-2250.dates.fict.example
-*.2250.dates.fict.example
-*.dates.fict.example
-*.fict.example
-.endd
-As soon as one key in the sequence is successfully looked up, the lookup
-finishes.
-
-.cindex "lookup" "partial matching &-- changing prefix"
-.cindex "prefix" "for partial matching"
-The use of &"*."& as the partial matching prefix is a default that can be
-changed. The motivation for this feature is to allow Exim to operate with file
-formats that are used by other MTAs. A different prefix can be supplied in
-parentheses instead of the hyphen after &"partial"&. For example:
-.code
-domains = partial(.)lsearch;/some/file
-.endd
-In this example, if the domain is &'a.b.c'&, the sequence of lookups is
-&`a.b.c`&, &`.a.b.c`&, and &`.b.c`& (the default minimum of 2 non-wild
-components is unchanged). The prefix may consist of any punctuation characters
-other than a closing parenthesis. It may be empty, for example:
-.code
-domains = partial1()cdb;/some/file
-.endd
-For this example, if the domain is &'a.b.c'&, the sequence of lookups is
-&`a.b.c`&, &`b.c`&, and &`c`&.
-
-If &"partial0"& is specified, what happens at the end (when the lookup with
-just one non-wild component has failed, and the original key is shortened right
-down to the null string) depends on the prefix:
-
-.ilist
-If the prefix has zero length, the whole lookup fails.
-.next
-If the prefix has length 1, a lookup for just the prefix is done. For
-example, the final lookup for &"partial0(.)"& is for &`.`& alone.
-.next
-Otherwise, if the prefix ends in a dot, the dot is removed, and the
-remainder is looked up. With the default prefix, therefore, the final lookup is
-for &"*"& on its own.
-.next
-Otherwise, the whole prefix is looked up.
-.endlist
-
-
-If the search type ends in &"*"& or &"*@"& (see section
-&<<SECTdefaultvaluelookups>>& above), the search for an ultimate default that
-this implies happens after all partial lookups have failed. If &"partial0"& is
-specified, adding &"*"& to the search type has no effect with the default
-prefix, because the &"*"& key is already included in the sequence of partial
-lookups. However, there might be a use for lookup types such as
-&"partial0(.)lsearch*"&.
-
-The use of &"*"& in lookup partial matching differs from its use as a wildcard
-in domain lists and the like. Partial matching works only in terms of
-dot-separated components; a key such as &`*fict.example`&
-in a database file is useless, because the asterisk in a partial matching
-subject key is always followed by a dot.
-
-
-
-
-.section "Lookup caching" "SECID64"
-.cindex "lookup" "caching"
-.cindex "caching" "lookup data"
-Exim caches all lookup results in order to avoid needless repetition of
-lookups. However, because (apart from the daemon) Exim operates as a collection
-of independent, short-lived processes, this caching applies only within a
-single Exim process. There is no inter-process lookup caching facility.
-
-For single-key lookups, Exim keeps the relevant files open in case there is
-another lookup that needs them. In some types of configuration this can lead to
-many files being kept open for messages with many recipients. To avoid hitting
-the operating system limit on the number of simultaneously open files, Exim
-closes the least recently used file when it needs to open more files than its
-own internal limit, which can be changed via the &%lookup_open_max%& option.
-
-The single-key lookup files are closed and the lookup caches are flushed at
-strategic points during delivery &-- for example, after all routing is
-complete.
-
-
-
-
-.section "Quoting lookup data" "SECID65"
-.cindex "lookup" "quoting"
-.cindex "quoting" "in lookups"
-When data from an incoming message is included in a query-style lookup, there
-is the possibility of special characters in the data messing up the syntax of
-the query. For example, a NIS+ query that contains
-.code
-[name=$local_part]
-.endd
-will be broken if the local part happens to contain a closing square bracket.
-For NIS+, data can be enclosed in double quotes like this:
-.code
-[name="$local_part"]
-.endd
-but this still leaves the problem of a double quote in the data. The rule for
-NIS+ is that double quotes must be doubled. Other lookup types have different
-rules, and to cope with the differing requirements, an expansion operator
-of the following form is provided:
-.code
-${quote_<lookup-type>:<string>}
-.endd
-For example, the safest way to write the NIS+ query is
-.code
-[name="${quote_nisplus:$local_part}"]
-.endd
-See chapter &<<CHAPexpand>>& for full coverage of string expansions. The quote
-operator can be used for all lookup types, but has no effect for single-key
-lookups, since no quoting is ever needed in their key strings.
-
-
-
-
-.section "More about dnsdb" "SECTdnsdb"
-.cindex "dnsdb lookup"
-.cindex "lookup" "dnsdb"
-.cindex "DNS" "as a lookup type"
-The &(dnsdb)& lookup type uses the DNS as its database. A simple query consists
-of a record type and a domain name, separated by an equals sign. For example,
-an expansion string could contain:
-.code
-${lookup dnsdb{mx=a.b.example}{$value}fail}
-.endd
-If the lookup succeeds, the result is placed in &$value$&, which in this case
-is used on its own as the result. If the lookup does not succeed, the
-&`fail`& keyword causes a &'forced expansion failure'& &-- see section
-&<<SECTforexpfai>>& for an explanation of what this means.
-
-The supported DNS record types are A, CNAME, MX, NS, PTR, SOA, SPF, SRV, TLSA
-and TXT, and, when Exim is compiled with IPv6 support, AAAA.
-If no type is given, TXT is assumed.
-
-For any record type, if multiple records are found, the data is returned as a
-concatenation, with newline as the default separator. The order, of course,
-depends on the DNS resolver. You can specify a different separator character
-between multiple records by putting a right angle-bracket followed immediately
-by the new separator at the start of the query. For example:
-.code
-${lookup dnsdb{>: a=host1.example}}
-.endd
-It is permitted to specify a space as the separator character. Further
-white space is ignored.
-For lookup types that return multiple fields per record,
-an alternate field separator can be specified using a comma after the main
-separator character, followed immediately by the field separator.
-
-.cindex "PTR record" "in &(dnsdb)& lookup"
-When the type is PTR,
-the data can be an IP address, written as normal; inversion and the addition of
-&%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example:
-.code
-${lookup dnsdb{ptr=192.168.4.5}{$value}fail}
-.endd
-If the data for a PTR record is not a syntactically valid IP address, it is not
-altered and nothing is added.
-
-.cindex "MX record" "in &(dnsdb)& lookup"
-.cindex "SRV record" "in &(dnsdb)& lookup"
-For an MX lookup, both the preference value and the host name are returned for
-each record, separated by a space. For an SRV lookup, the priority, weight,
-port, and host name are returned for each record, separated by spaces.
-The field separator can be modified as above.
-
-.cindex "TXT record" "in &(dnsdb)& lookup"
-.cindex "SPF record" "in &(dnsdb)& lookup"
-For TXT records with multiple items of data, only the first item is returned,
-unless a field separator is specified.
-To concatenate items without a separator, use a semicolon instead.
-For SPF records the
-default behaviour is to concatenate multiple items without using a separator.
-.code
-${lookup dnsdb{>\n,: txt=a.b.example}}
-${lookup dnsdb{>\n; txt=a.b.example}}
-${lookup dnsdb{spf=example.org}}
-.endd
-It is permitted to specify a space as the separator character. Further
-white space is ignored.
-
-.cindex "SOA record" "in &(dnsdb)& lookup"
-For an SOA lookup, while no result is obtained the lookup is redone with
-successively more leading components dropped from the given domain.
-Only the primary-nameserver field is returned unless a field separator is
-specified.
-.code
-${lookup dnsdb{>:,; soa=a.b.example.com}}
-.endd
-
-.section "Dnsdb lookup modifiers" "SECTdnsdb_mod"
-.cindex "dnsdb modifiers"
-.cindex "modifiers" "dnsdb"
-.cindex "options" "dnsdb"
-Modifiers for &(dnsdb)& lookups are given by optional keywords,
-each followed by a comma,
-that may appear before the record type.
-
-The &(dnsdb)& lookup fails only if all the DNS lookups fail. If there is a
-temporary DNS error for any of them, the behaviour is controlled by
-a defer-option modifier.
-The possible keywords are
-&"defer_strict"&, &"defer_never"&, and &"defer_lax"&.
-With &"strict"& behaviour, any temporary DNS error causes the
-whole lookup to defer. With &"never"& behaviour, a temporary DNS error is
-ignored, and the behaviour is as if the DNS lookup failed to find anything.
-With &"lax"& behaviour, all the queries are attempted, but a temporary DNS
-error causes the whole lookup to defer only if none of the other lookups
-succeed. The default is &"lax"&, so the following lookups are equivalent:
-.code
-${lookup dnsdb{defer_lax,a=one.host.com:two.host.com}}
-${lookup dnsdb{a=one.host.com:two.host.com}}
-.endd
-Thus, in the default case, as long as at least one of the DNS lookups
-yields some data, the lookup succeeds.
-
-.cindex "DNSSEC" "dns lookup"
-Use of &(DNSSEC)& is controlled by a dnssec modifier.
-The possible keywords are
-&"dnssec_strict"&, &"dnssec_lax"&, and &"dnssec_never"&.
-With &"strict"& or &"lax"& DNSSEC information is requested
-with the lookup.
-With &"strict"& a response from the DNS resolver that
-is not labelled as authenticated data
-is treated as equivalent to a temporary DNS error.
-The default is &"lax"&.
-
-See also the &$lookup_dnssec_authenticated$& variable.
-
-.cindex timeout "dns lookup"
-.cindex "DNS" timeout
-Timeout for the dnsdb lookup can be controlled by a retrans modifier.
-The form is &"retrans_VAL"& where VAL is an Exim time specification
-(e.g. &"5s"&).
-The default value is set by the main configuration option &%dns_retrans%&.
-
-Retries for the dnsdb lookup can be controlled by a retry modifier.
-The form if &"retry_VAL"& where VAL is an integer.
-The default count is set by the main configuration option &%dns_retry%&.
-
-.cindex caching "of dns lookup"
-.cindex TTL "of dns lookup"
-.cindex DNS TTL
-Dnsdb lookup results are cached within a single process (and its children).
-The cache entry lifetime is limited to the smallest time-to-live (TTL)
-value of the set of returned DNS records.
-
-
-.section "Pseudo dnsdb record types" "SECID66"
-.cindex "MX record" "in &(dnsdb)& lookup"
-By default, both the preference value and the host name are returned for
-each MX record, separated by a space. If you want only host names, you can use
-the pseudo-type MXH:
-.code
-${lookup dnsdb{mxh=a.b.example}}
-.endd
-In this case, the preference values are omitted, and just the host names are
-returned.
-
-.cindex "name server for enclosing domain"
-Another pseudo-type is ZNS (for &"zone NS"&). It performs a lookup for NS
-records on the given domain, but if none are found, it removes the first
-component of the domain name, and tries again. This process continues until NS
-records are found or there are no more components left (or there is a DNS
-error). In other words, it may return the name servers for a top-level domain,
-but it never returns the root name servers. If there are no NS records for the
-top-level domain, the lookup fails. Consider these examples:
-.code
-${lookup dnsdb{zns=xxx.quercite.com}}
-${lookup dnsdb{zns=xxx.edu}}
-.endd
-Assuming that in each case there are no NS records for the full domain name,
-the first returns the name servers for &%quercite.com%&, and the second returns
-the name servers for &%edu%&.
-
-You should be careful about how you use this lookup because, unless the
-top-level domain does not exist, the lookup always returns some host names. The
-sort of use to which this might be put is for seeing if the name servers for a
-given domain are on a blacklist. You can probably assume that the name servers
-for the high-level domains such as &%com%& or &%co.uk%& are not going to be on
-such a list.
-
-.cindex "CSA" "in &(dnsdb)& lookup"
-A third pseudo-type is CSA (Client SMTP Authorization). This looks up SRV
-records according to the CSA rules, which are described in section
-&<<SECTverifyCSA>>&. Although &(dnsdb)& supports SRV lookups directly, this is
-not sufficient because of the extra parent domain search behaviour of CSA. The
-result of a successful lookup such as:
-.code
-${lookup dnsdb {csa=$sender_helo_name}}
-.endd
-has two space-separated fields: an authorization code and a target host name.
-The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
-authorization required but absent, or &"?"& for unknown.
-
-.cindex "A+" "in &(dnsdb)& lookup"
-The pseudo-type A+ performs an AAAA
-and then an A lookup.  All results are returned; defer processing
-(see below) is handled separately for each lookup.  Example:
-.code
-${lookup dnsdb {>; a+=$sender_helo_name}}
-.endd
-
-
-.section "Multiple dnsdb lookups" "SECID67"
-In the previous sections, &(dnsdb)& lookups for a single domain are described.
-However, you can specify a list of domains or IP addresses in a single
-&(dnsdb)& lookup. The list is specified in the normal Exim way, with colon as
-the default separator, but with the ability to change this. For example:
-.code
-${lookup dnsdb{one.domain.com:two.domain.com}}
-${lookup dnsdb{a=one.host.com:two.host.com}}
-${lookup dnsdb{ptr = <; 1.2.3.4 ; 4.5.6.8}}
-.endd
-In order to retain backwards compatibility, there is one special case: if
-the lookup type is PTR and no change of separator is specified, Exim looks
-to see if the rest of the string is precisely one IPv6 address. In this
-case, it does not treat it as a list.
-
-The data from each lookup is concatenated, with newline separators by default,
-in the same way that multiple DNS records for a single item are handled. A
-different separator can be specified, as described above.
-
-
-
-
-.section "More about LDAP" "SECTldap"
-.cindex "LDAP" "lookup, more about"
-.cindex "lookup" "LDAP"
-.cindex "Solaris" "LDAP"
-The original LDAP implementation came from the University of Michigan; this has
-become &"Open LDAP"&, and there are now two different releases. Another
-implementation comes from Netscape, and Solaris 7 and subsequent releases
-contain inbuilt LDAP support. Unfortunately, though these are all compatible at
-the lookup function level, their error handling is different. For this reason
-it is necessary to set a compile-time variable when building Exim with LDAP, to
-indicate which LDAP library is in use. One of the following should appear in
-your &_Local/Makefile_&:
-.code
-LDAP_LIB_TYPE=UMICHIGAN
-LDAP_LIB_TYPE=OPENLDAP1
-LDAP_LIB_TYPE=OPENLDAP2
-LDAP_LIB_TYPE=NETSCAPE
-LDAP_LIB_TYPE=SOLARIS
-.endd
-If LDAP_LIB_TYPE is not set, Exim assumes &`OPENLDAP1`&, which has the
-same interface as the University of Michigan version.
-
-There are three LDAP lookup types in Exim. These behave slightly differently in
-the way they handle the results of a query:
-
-.ilist
-&(ldap)& requires the result to contain just one entry; if there are more, it
-gives an error.
-.next
-&(ldapdn)& also requires the result to contain just one entry, but it is the
-Distinguished Name that is returned rather than any attribute values.
-.next
-&(ldapm)& permits the result to contain more than one entry; the attributes
-from all of them are returned.
-.endlist
-
-
-For &(ldap)& and &(ldapm)&, if a query finds only entries with no attributes,
-Exim behaves as if the entry did not exist, and the lookup fails. The format of
-the data returned by a successful lookup is described in the next section.
-First we explain how LDAP queries are coded.
-
-
-.section "Format of LDAP queries" "SECTforldaque"
-.cindex "LDAP" "query format"
-An LDAP query takes the form of a URL as defined in RFC 2255. For example, in
-the configuration of a &(redirect)& router one might have this setting:
-.code
-data = ${lookup ldap \
-  {ldap:///cn=$local_part,o=University%20of%20Cambridge,\
-  c=UK?mailbox?base?}}
-.endd
-.cindex "LDAP" "with TLS"
-The URL may begin with &`ldap`& or &`ldaps`& if your LDAP library supports
-secure (encrypted) LDAP connections. The second of these ensures that an
-encrypted TLS connection is used.
-
-With sufficiently modern LDAP libraries, Exim supports forcing TLS over regular
-LDAP connections, rather than the SSL-on-connect &`ldaps`&.
-See the &%ldap_start_tls%& option.
-
-Starting with Exim 4.83, the initialization of LDAP with TLS is more tightly
-controlled. Every part of the TLS configuration can be configured by settings in
-&_exim.conf_&. Depending on the version of the client libraries installed on
-your system, some of the initialization may have required setting options in
-&_/etc/ldap.conf_& or &_~/.ldaprc_& to get TLS working with self-signed
-certificates. This revealed a nuance where the current UID that exim was
-running as could affect which config files it read. With Exim 4.83, these
-methods become optional, only taking effect if not specifically set in
-&_exim.conf_&.
-
-
-.section "LDAP quoting" "SECID68"
-.cindex "LDAP" "quoting"
-Two levels of quoting are required in LDAP queries, the first for LDAP itself
-and the second because the LDAP query is represented as a URL. Furthermore,
-within an LDAP query, two different kinds of quoting are required. For this
-reason, there are two different LDAP-specific quoting operators.
-
-The &%quote_ldap%& operator is designed for use on strings that are part of
-filter specifications. Conceptually, it first does the following conversions on
-the string:
-.code
-*   =>   \2A
-(   =>   \28
-)   =>   \29
-\   =>   \5C
-.endd
-in accordance with RFC 2254. The resulting string is then quoted according
-to the rules for URLs, that is, all non-alphanumeric characters except
-.code
-! $ ' - . _ ( ) * +
-.endd
-are converted to their hex values, preceded by a percent sign. For example:
-.code
-${quote_ldap: a(bc)*, a<yz>; }
-.endd
-yields
-.code
-%20a%5C28bc%5C29%5C2A%2C%20a%3Cyz%3E%3B%20
-.endd
-Removing the URL quoting, this is (with a leading and a trailing space):
-.code
-a\28bc\29\2A, a<yz>;
-.endd
-The &%quote_ldap_dn%& operator is designed for use on strings that are part of
-base DN specifications in queries. Conceptually, it first converts the string
-by inserting a backslash in front of any of the following characters:
-.code
-, + " \ < > ;
-.endd
-It also inserts a backslash before any leading spaces or # characters, and
-before any trailing spaces. (These rules are in RFC 2253.) The resulting string
-is then quoted according to the rules for URLs. For example:
-.code
-${quote_ldap_dn: a(bc)*, a<yz>; }
-.endd
-yields
-.code
-%5C%20a(bc)*%5C%2C%20a%5C%3Cyz%5C%3E%5C%3B%5C%20
-.endd
-Removing the URL quoting, this is (with a trailing space):
-.code
-\ a(bc)*\, a\<yz\>\;\
-.endd
-There are some further comments about quoting in the section on LDAP
-authentication below.
-
-
-.section "LDAP connections" "SECID69"
-.cindex "LDAP" "connections"
-The connection to an LDAP server may either be over TCP/IP, or, when OpenLDAP
-is in use, via a Unix domain socket. The example given above does not specify
-an LDAP server. A server that is reached by TCP/IP can be specified in a query
-by starting it with
-.code
-ldap://<hostname>:<port>/...
-.endd
-If the port (and preceding colon) are omitted, the standard LDAP port (389) is
-used. When no server is specified in a query, a list of default servers is
-taken from the &%ldap_default_servers%& configuration option. This supplies a
-colon-separated list of servers which are tried in turn until one successfully
-handles a query, or there is a serious error. Successful handling either
-returns the requested data, or indicates that it does not exist. Serious errors
-are syntactical, or multiple values when only a single value is expected.
-Errors which cause the next server to be tried are connection failures, bind
-failures, and timeouts.
-
-For each server name in the list, a port number can be given. The standard way
-of specifying a host and port is to use a colon separator (RFC 1738). Because
-&%ldap_default_servers%& is a colon-separated list, such colons have to be
-doubled. For example
-.code
-ldap_default_servers = ldap1.example.com::145:ldap2.example.com
-.endd
-If &%ldap_default_servers%& is unset, a URL with no server name is passed
-to the LDAP library with no server name, and the library's default (normally
-the local host) is used.
-
-If you are using the OpenLDAP library, you can connect to an LDAP server using
-a Unix domain socket instead of a TCP/IP connection. This is specified by using
-&`ldapi`& instead of &`ldap`& in LDAP queries. What follows here applies only
-to OpenLDAP. If Exim is compiled with a different LDAP library, this feature is
-not available.
-
-For this type of connection, instead of a host name for the server, a pathname
-for the socket is required, and the port number is not relevant. The pathname
-can be specified either as an item in &%ldap_default_servers%&, or inline in
-the query. In the former case, you can have settings such as
-.code
-ldap_default_servers = /tmp/ldap.sock : backup.ldap.your.domain
-.endd
-When the pathname is given in the query, you have to escape the slashes as
-&`%2F`& to fit in with the LDAP URL syntax. For example:
-.code
-${lookup ldap {ldapi://%2Ftmp%2Fldap.sock/o=...
-.endd
-When Exim processes an LDAP lookup and finds that the &"hostname"& is really
-a pathname, it uses the Unix domain socket code, even if the query actually
-specifies &`ldap`& or &`ldaps`&. In particular, no encryption is used for a
-socket connection. This behaviour means that you can use a setting of
-&%ldap_default_servers%& such as in the example above with traditional &`ldap`&
-or &`ldaps`& queries, and it will work. First, Exim tries a connection via
-the Unix domain socket; if that fails, it tries a TCP/IP connection to the
-backup host.
-
-If an explicit &`ldapi`& type is given in a query when a host name is
-specified, an error is diagnosed. However, if there are more items in
-&%ldap_default_servers%&, they are tried. In other words:
-
-.ilist
-Using a pathname with &`ldap`& or &`ldaps`& forces the use of the Unix domain
-interface.
-.next
-Using &`ldapi`& with a host name causes an error.
-.endlist
-
-
-Using &`ldapi`& with no host or path in the query, and no setting of
-&%ldap_default_servers%&, does whatever the library does by default.
-
-
-
-.section "LDAP authentication and control information" "SECID70"
-.cindex "LDAP" "authentication"
-The LDAP URL syntax provides no way of passing authentication and other control
-information to the server. To make this possible, the URL in an LDAP query may
-be preceded by any number of <&'name'&>=<&'value'&> settings, separated by
-spaces. If a value contains spaces it must be enclosed in double quotes, and
-when double quotes are used, backslash is interpreted in the usual way inside
-them. The following names are recognized:
-.display
-&`DEREFERENCE`&  set the dereferencing parameter
-&`NETTIME    `&  set a timeout for a network operation
-&`USER       `&  set the DN, for authenticating the LDAP bind
-&`PASS       `&  set the password, likewise
-&`REFERRALS  `&  set the referrals parameter
-&`SERVERS    `&  set alternate server list for this query only
-&`SIZE       `&  set the limit for the number of entries returned
-&`TIME       `&  set the maximum waiting time for a query
-.endd
-The value of the DEREFERENCE parameter must be one of the words &"never"&,
-&"searching"&, &"finding"&, or &"always"&. The value of the REFERRALS parameter
-must be &"follow"& (the default) or &"nofollow"&. The latter stops the LDAP
-library from trying to follow referrals issued by the LDAP server.
-
-.cindex LDAP timeout
-.cindex timeout "LDAP lookup"
-The name CONNECT is an obsolete name for NETTIME, retained for
-backwards compatibility. This timeout (specified as a number of seconds) is
-enforced from the client end for operations that can be carried out over a
-network. Specifically, it applies to network connections and calls to the
-&'ldap_result()'& function. If the value is greater than zero, it is used if
-LDAP_OPT_NETWORK_TIMEOUT is defined in the LDAP headers (OpenLDAP), or
-if LDAP_X_OPT_CONNECT_TIMEOUT is defined in the LDAP headers (Netscape
-SDK 4.1). A value of zero forces an explicit setting of &"no timeout"& for
-Netscape SDK; for OpenLDAP no action is taken.
-
-The TIME parameter (also a number of seconds) is passed to the server to
-set a server-side limit on the time taken to complete a search.
-
-The SERVERS parameter allows you to specify an alternate list of ldap servers
-to use for an individual lookup.  The global &%ldap_default_servers%& option provides a
-default list of ldap servers, and a single lookup can specify a single ldap
-server to use.  But when you need to do a lookup with a list of servers that is
-different than the default list (maybe different order, maybe a completely
-different set of servers), the SERVERS parameter allows you to specify this
-alternate list (colon-separated).
-
-Here is an example of an LDAP query in an Exim lookup that uses some of these
-values. This is a single line, folded to fit on the page:
-.code
-${lookup ldap
-  {user="cn=manager,o=University of Cambridge,c=UK" pass=secret
-  ldap:///o=University%20of%20Cambridge,c=UK?sn?sub?(cn=foo)}
-  {$value}fail}
-.endd
-The encoding of spaces as &`%20`& is a URL thing which should not be done for
-any of the auxiliary data. Exim configuration settings that include lookups
-which contain password information should be preceded by &"hide"& to prevent
-non-admin users from using the &%-bP%& option to see their values.
-
-The auxiliary data items may be given in any order. The default is no
-connection timeout (the system timeout is used), no user or password, no limit
-on the number of entries returned, and no time limit on queries.
-
-When a DN is quoted in the USER= setting for LDAP authentication, Exim
-removes any URL quoting that it may contain before passing it LDAP. Apparently
-some libraries do this for themselves, but some do not. Removing the URL
-quoting has two advantages:
-
-.ilist
-It makes it possible to use the same &%quote_ldap_dn%& expansion for USER=
-DNs as with DNs inside actual queries.
-.next
-It permits spaces inside USER= DNs.
-.endlist
-
-For example, a setting such as
-.code
-USER=cn=${quote_ldap_dn:$1}
-.endd
-should work even if &$1$& contains spaces.
-
-Expanded data for the PASS= value should be quoted using the &%quote%&
-expansion operator, rather than the LDAP quote operators. The only reason this
-field needs quoting is to ensure that it conforms to the Exim syntax, which
-does not allow unquoted spaces. For example:
-.code
-PASS=${quote:$3}
-.endd
-The LDAP authentication mechanism can be used to check passwords as part of
-SMTP authentication. See the &%ldapauth%& expansion string condition in chapter
-&<<CHAPexpand>>&.
-
-
-
-.section "Format of data returned by LDAP" "SECID71"
-.cindex "LDAP" "returned data formats"
-The &(ldapdn)& lookup type returns the Distinguished Name from a single entry
-as a sequence of values, for example
-.code
-cn=manager,o=University of Cambridge,c=UK
-.endd
-The &(ldap)& lookup type generates an error if more than one entry matches the
-search filter, whereas &(ldapm)& permits this case, and inserts a newline in
-the result between the data from different entries. It is possible for multiple
-values to be returned for both &(ldap)& and &(ldapm)&, but in the former case
-you know that whatever values are returned all came from a single entry in the
-directory.
-
-In the common case where you specify a single attribute in your LDAP query, the
-result is not quoted, and does not contain the attribute name. If the attribute
-has multiple values, they are separated by commas. Any comma that is
-part of an attribute's value is doubled.
-
-If you specify multiple attributes, the result contains space-separated, quoted
-strings, each preceded by the attribute name and an equals sign. Within the
-quotes, the quote character, backslash, and newline are escaped with
-backslashes, and commas are used to separate multiple values for the attribute.
-Any commas in attribute values are doubled
-(permitting treatment of the values as a comma-separated list).
-Apart from the escaping, the string within quotes takes the same form as the
-output when a single attribute is requested. Specifying no attributes is the
-same as specifying all of an entry's attributes.
-
-Here are some examples of the output format. The first line of each pair is an
-LDAP query, and the second is the data that is returned. The attribute called
-&%attr1%& has two values, one of them with an embedded comma, whereas
-&%attr2%& has only one value. Both attributes are derived from &%attr%&
-(they have SUP &%attr%& in their schema definitions).
-
-.code
-ldap:///o=base?attr1?sub?(uid=fred)
-value1.1,value1,,2
-
-ldap:///o=base?attr2?sub?(uid=fred)
-value two
-
-ldap:///o=base?attr?sub?(uid=fred)
-value1.1,value1,,2,value two
-
-ldap:///o=base?attr1,attr2?sub?(uid=fred)
-attr1="value1.1,value1,,2" attr2="value two"
-
-ldap:///o=base??sub?(uid=fred)
-objectClass="top" attr1="value1.1,value1,,2" attr2="value two"
-.endd
-You can
-make use of Exim's &%-be%& option to run expansion tests and thereby check the
-results of LDAP lookups.
-The &%extract%& operator in string expansions can be used to pick out
-individual fields from data that consists of &'key'&=&'value'& pairs.
-The &%listextract%& operator should be used to pick out individual values
-of attributes, even when only a single value is expected.
-The doubling of embedded commas allows you to use the returned data as a
-comma separated list (using the "<," syntax for changing the input list separator).
-
-
-
-
-.section "More about NIS+" "SECTnisplus"
-.cindex "NIS+ lookup type"
-.cindex "lookup" "NIS+"
-NIS+ queries consist of a NIS+ &'indexed name'& followed by an optional colon
-and field name. If this is given, the result of a successful query is the
-contents of the named field; otherwise the result consists of a concatenation
-of &'field-name=field-value'& pairs, separated by spaces. Empty values and
-values containing spaces are quoted. For example, the query
-.code
-[name=mg1456],passwd.org_dir
-.endd
-might return the string
-.code
-name=mg1456 passwd="" uid=999 gid=999 gcos="Martin Guerre"
-home=/home/mg1456 shell=/bin/bash shadow=""
-.endd
-(split over two lines here to fit on the page), whereas
-.code
-[name=mg1456],passwd.org_dir:gcos
-.endd
-would just return
-.code
-Martin Guerre
-.endd
-with no quotes. A NIS+ lookup fails if NIS+ returns more than one table entry
-for the given indexed key. The effect of the &%quote_nisplus%& expansion
-operator is to double any quote characters within the text.
-
-
-
-.section "SQL lookups" "SECTsql"
-.cindex "SQL lookup types"
-.cindex "MySQL" "lookup type"
-.cindex "PostgreSQL lookup type"
-.cindex "lookup" "MySQL"
-.cindex "lookup" "PostgreSQL"
-.cindex "Oracle" "lookup type"
-.cindex "lookup" "Oracle"
-.cindex "InterBase lookup type"
-.cindex "lookup" "InterBase"
-.cindex "Redis lookup type"
-.cindex lookup Redis
-Exim can support lookups in InterBase, MySQL, Oracle, PostgreSQL, Redis,
-and SQLite
-databases. Queries for these databases contain SQL statements, so an example
-might be
-.code
-${lookup mysql{select mailbox from users where id='userx'}\
-  {$value}fail}
-.endd
-If the result of the query contains more than one field, the data for each
-field in the row is returned, preceded by its name, so the result of
-.code
-${lookup pgsql{select home,name from users where id='userx'}\
-  {$value}}
-.endd
-might be
-.code
-home=/home/userx name="Mister X"
-.endd
-Empty values and values containing spaces are double quoted, with embedded
-quotes escaped by a backslash. If the result of the query contains just one
-field, the value is passed back verbatim, without a field name, for example:
-.code
-Mister X
-.endd
-If the result of the query yields more than one row, it is all concatenated,
-with a newline between the data for each row.
-
-
-.section "More about MySQL, PostgreSQL, Oracle, InterBase, and Redis" "SECID72"
-.cindex "MySQL" "lookup type"
-.cindex "PostgreSQL lookup type"
-.cindex "lookup" "MySQL"
-.cindex "lookup" "PostgreSQL"
-.cindex "Oracle" "lookup type"
-.cindex "lookup" "Oracle"
-.cindex "InterBase lookup type"
-.cindex "lookup" "InterBase"
-.cindex "Redis lookup type"
-.cindex lookup Redis
-If any MySQL, PostgreSQL, Oracle, InterBase or Redis lookups are used, the
-&%mysql_servers%&, &%pgsql_servers%&, &%oracle_servers%&, &%ibase_servers%&,
-or &%redis_servers%&
-option (as appropriate) must be set to a colon-separated list of server
-information.
-.oindex &%mysql_servers%&
-.oindex &%pgsql_servers%&
-.oindex &%oracle_servers%&
-.oindex &%ibase_servers%&
-.oindex &%redis_servers%&
-(For MySQL and PostgreSQL, the global option need not be set if all
-queries contain their own server information &-- see section
-&<<SECTspeserque>>&.)
-For all but Redis
-each item in the list is a slash-separated list of four
-items: host name, database name, user name, and password. In the case of
-Oracle, the host name field is used for the &"service name"&, and the database
-name field is not used and should be empty. For example:
-.code
-hide oracle_servers = oracle.plc.example//userx/abcdwxyz
-.endd
-Because password data is sensitive, you should always precede the setting with
-&"hide"&, to prevent non-admin users from obtaining the setting via the &%-bP%&
-option. Here is an example where two MySQL servers are listed:
-.code
-hide mysql_servers = localhost/users/root/secret:\
-                     otherhost/users/root/othersecret
-.endd
-For MySQL and PostgreSQL, a host may be specified as <&'name'&>:<&'port'&> but
-because this is a colon-separated list, the colon has to be doubled. For each
-query, these parameter groups are tried in order until a connection is made and
-a query is successfully processed. The result of a query may be that no data is
-found, but that is still a successful query. In other words, the list of
-servers provides a backup facility, not a list of different places to look.
-
-For Redis the global option need not be specified if all queries contain their
-own server information &-- see section &<<SECTspeserque>>&.
-If specified, the option must be set to a colon-separated list of server
-information.
-Each item in the list is a slash-separated list of three items:
-host, database number, and password.
-.olist
-The host is required and may be either an IPv4 address and optional
-port number (separated by a colon, which needs doubling due to the
-higher-level list), or a Unix socket pathname enclosed in parentheses
-.next
-The database number is optional; if present that number is selected in the backend
-.next
-The password is optional; if present it is used to authenticate to the backend
-.endlist
-
-The &%quote_mysql%&, &%quote_pgsql%&, and &%quote_oracle%& expansion operators
-convert newline, tab, carriage return, and backspace to \n, \t, \r, and \b
-respectively, and the characters single-quote, double-quote, and backslash
-itself are escaped with backslashes.
-
-The &%quote_redis%& expansion operator
-escapes whitespace and backslash characters with a backslash.
-
-.section "Specifying the server in the query" "SECTspeserque"
-.new
-For MySQL, PostgreSQL and Redis lookups (but not currently for Oracle and InterBase),
-it is possible to specify a list of servers with an individual query. This is
-done by appending a comma-separated option to the query type:
-.display
-.endd
-&`,servers=`&&'server1:server2:server3:...'&
-.wen
-Each item in the list may take one of two forms:
-.olist
-If it contains no slashes it is assumed to be just a host name. The appropriate
-global option (&%mysql_servers%& or &%pgsql_servers%&) is searched for a host
-of the same name, and the remaining parameters (database, user, password) are
-taken from there.
-.next
-If it contains any slashes, it is taken as a complete parameter set.
-.endlist
-The list of servers is used in exactly the same way as the global list.
-Once a connection to a server has happened and a query has been
-successfully executed, processing of the lookup ceases.
-
-This feature is intended for use in master/slave situations where updates
-are occurring and you want to update the master rather than a slave. If the
-master is in the list as a backup for reading, you might have a global setting
-like this:
-.code
-mysql_servers = slave1/db/name/pw:\
-                slave2/db/name/pw:\
-                master/db/name/pw
-.endd
-In an updating lookup, you could then write:
-.code
-${lookup mysql,servers=master {UPDATE ...} }
-.endd
-That query would then be sent only to the master server. If, on the other hand,
-the master is not to be used for reading, and so is not present in the global
-option, you can still update it by a query of this form:
-.code
-${lookup pgsql,servers=master/db/name/pw {UPDATE ...} }
-.endd
-
-.new
-An older syntax places the servers speciification before the qury,
-semicolon separated:
-.code
-${lookup mysql{servers=master; UPDATE ...} }
-.endd
-The new version avoids potential issues with tainted
-arguments in the query, for explicit expansion.
-&*Note*&: server specifications in list-style lookups are still problematic.
-.wen
-
-
-.section "Special MySQL features" "SECID73"
-For MySQL, an empty host name or the use of &"localhost"& in &%mysql_servers%&
-causes a connection to the server on the local host by means of a Unix domain
-socket. An alternate socket can be specified in parentheses.
-An option group name for MySQL option files can be specified in square brackets;
-the default value is &"exim"&.
-The full syntax of each item in &%mysql_servers%& is:
-.display
-<&'hostname'&>::<&'port'&>(<&'socket name'&>)[<&'option group'&>]/&&&
-  <&'database'&>/<&'user'&>/<&'password'&>
-.endd
-Any of the four sub-parts of the first field can be omitted. For normal use on
-the local host it can be left blank or set to just &"localhost"&.
-
-No database need be supplied &-- but if it is absent here, it must be given in
-the queries.
-
-If a MySQL query is issued that does not request any data (an insert, update,
-or delete command), the result of the lookup is the number of rows affected.
-
-&*Warning*&: This can be misleading. If an update does not actually change
-anything (for example, setting a field to the value it already has), the result
-is zero because no rows are affected.
-
-
-.section "Special PostgreSQL features" "SECID74"
-PostgreSQL lookups can also use Unix domain socket connections to the database.
-This is usually faster and costs less CPU time than a TCP/IP connection.
-However it can be used only if the mail server runs on the same machine as the
-database server. A configuration line for PostgreSQL via Unix domain sockets
-looks like this:
-.code
-hide pgsql_servers = (/tmp/.s.PGSQL.5432)/db/user/password : ...
-.endd
-In other words, instead of supplying a host name, a path to the socket is
-given. The path name is enclosed in parentheses so that its slashes aren't
-visually confused with the delimiters for the other server parameters.
-
-If a PostgreSQL query is issued that does not request any data (an insert,
-update, or delete command), the result of the lookup is the number of rows
-affected.
-
-.section "More about SQLite" "SECTsqlite"
-.cindex "lookup" "SQLite"
-.cindex "sqlite lookup type"
-SQLite is different to the other SQL lookups because a filename is required in
-addition to the SQL query. An SQLite database is a single file, and there is no
-daemon as in the other SQL databases.
-
-.new
-.oindex &%sqlite_dbfile%&
-The preferred way of specifying the file is by using the 
-&%sqlite_dbfile%& option, set to
-an absolute path.
-.wen
-A deprecated method is available, prefixing the query with the filename
-separated by white space.
-This means that the path name cannot contain white space.
-.cindex "tainted data" "sqlite file"
-It also means that the query cannot use any tainted values, as that taints
-the entire query including the filename - resulting in a refusal to open
-the file.
-
-.new
-Here is a lookup expansion example:
-.code
-sqlite_dbfile = /some/thing/sqlitedb
-...
-${lookup sqlite {select name from aliases where id='userx';}}
-.endd
-In a list, the syntax is similar. For example:
-.code
-domainlist relay_to_domains = sqlite;\
-   select * from relays where ip='$sender_host_address';
-.endd
-.wen
-The only character affected by the &%quote_sqlite%& operator is a single
-quote, which it doubles.
-
-.cindex timeout SQLite
-.cindex sqlite "lookup timeout"
-The SQLite library handles multiple simultaneous accesses to the database
-internally. Multiple readers are permitted, but only one process can
-update at once. Attempts to access the database while it is being updated
-are rejected after a timeout period, during which the SQLite library
-waits for the lock to be released. In Exim, the default timeout is set
-to 5 seconds, but it can be changed by means of the &%sqlite_lock_timeout%&
-option.
-
-.section "More about Redis" "SECTredis"
-.cindex "lookup" "Redis"
-.cindex "redis lookup type"
-Redis is a non-SQL database. Commands are simple get and set.
-Examples:
-.code
-${lookup redis{set keyname ${quote_redis:objvalue plus}}}
-${lookup redis{get keyname}}
-.endd
-
-As of release 4.91, "lightweight" support for Redis Cluster is available.
-Requires &%redis_servers%& list to contain all the servers in the cluster, all
-of which must be reachable from the running exim instance. If the cluster has
-master/slave replication, the list must contain all the master and slave
-servers.
-
-When the Redis Cluster returns a "MOVED" response to a query, Exim does not
-immediately follow the redirection but treats the response as a DEFER, moving on
-to the next server in the &%redis_servers%& list until the correct server is
-reached.
-
-.ecindex IIDfidalo1
-.ecindex IIDfidalo2
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "Domain, host, address, and local part lists" &&&
-         "CHAPdomhosaddlists" &&&
-         "Domain, host, and address lists"
-.scindex IIDdohoadli "lists of domains; hosts; etc."
-A number of Exim configuration options contain lists of domains, hosts,
-email addresses, or local parts. For example, the &%hold_domains%& option
-contains a list of domains whose delivery is currently suspended. These lists
-are also used as data in ACL statements (see chapter &<<CHAPACL>>&), and as
-arguments to expansion conditions such as &%match_domain%&.
-
-Each item in one of these lists is a pattern to be matched against a domain,
-host, email address, or local part, respectively. In the sections below, the
-different types of pattern for each case are described, but first we cover some
-general facilities that apply to all four kinds of list.
-
-Note that other parts of Exim use a &'string list'& which does not
-support all the complexity available in
-domain, host, address and local part lists.
-
-
-
-.section "Expansion of lists" "SECTlistexpand"
-.cindex "expansion" "of lists"
-Each list is expanded as a single string before it is used.
-
-&'Exception: the router headers_remove option, where list-item
-splitting is done before string-expansion.'&
-
-The result of
-expansion must be a list, possibly containing empty items, which is split up
-into separate items for matching. By default, colon is the separator character,
-but this can be varied if necessary. See sections &<<SECTlistconstruct>>& and
-&<<SECTempitelis>>& for details of the list syntax; the second of these
-discusses the way to specify empty list items.
-
-
-If the string expansion is forced to fail, Exim behaves as if the item it is
-testing (domain, host, address, or local part) is not in the list. Other
-expansion failures cause temporary errors.
-
-If an item in a list is a regular expression, backslashes, dollars and possibly
-other special characters in the expression must be protected against
-misinterpretation by the string expander. The easiest way to do this is to use
-the &`\N`& expansion feature to indicate that the contents of the regular
-expression should not be expanded. For example, in an ACL you might have:
-.code
-deny senders = \N^\d{8}\w@.*\.baddomain\.example$\N : \
-               ${lookup{$domain}lsearch{/badsenders/bydomain}}
-.endd
-The first item is a regular expression that is protected from expansion by
-&`\N`&, whereas the second uses the expansion to obtain a list of unwanted
-senders based on the receiving domain.
-
-
-
-
-.section "Negated items in lists" "SECID76"
-.cindex "list" "negation"
-.cindex "negation" "in lists"
-Items in a list may be positive or negative. Negative items are indicated by a
-leading exclamation mark, which may be followed by optional white space. A list
-defines a set of items (domains, etc). When Exim processes one of these lists,
-it is trying to find out whether a domain, host, address, or local part
-(respectively) is in the set that is defined by the list. It works like this:
-
-The list is scanned from left to right. If a positive item is matched, the
-subject that is being checked is in the set; if a negative item is matched, the
-subject is not in the set. If the end of the list is reached without the
-subject having matched any of the patterns, it is in the set if the last item
-was a negative one, but not if it was a positive one. For example, the list in
-.code
-domainlist relay_to_domains = !a.b.c : *.b.c
-.endd
-matches any domain ending in &'.b.c'& except for &'a.b.c'&. Domains that match
-neither &'a.b.c'& nor &'*.b.c'& do not match, because the last item in the
-list is positive. However, if the setting were
-.code
-domainlist relay_to_domains = !a.b.c
-.endd
-then all domains other than &'a.b.c'& would match because the last item in the
-list is negative. In other words, a list that ends with a negative item behaves
-as if it had an extra item &`:*`& on the end.
-
-Another way of thinking about positive and negative items in lists is to read
-the connector as &"or"& after a positive item and as &"and"& after a negative
-item.
-
-
-
-.section "File names in lists" "SECTfilnamlis"
-.cindex "list" "filename in"
-If an item in a domain, host, address, or local part list is an absolute
-filename (beginning with a slash character), each line of the file is read and
-processed as if it were an independent item in the list, except that further
-filenames are not allowed,
-and no expansion of the data from the file takes place.
-Empty lines in the file are ignored, and the file may also contain comment
-lines:
-
-.ilist
-For domain and host lists, if a # character appears anywhere in a line of the
-file, it and all following characters are ignored.
-.next
-Because local parts may legitimately contain # characters, a comment in an
-address list or local part list file is recognized only if # is preceded by
-white space or the start of the line. For example:
-.code
-not#comment@x.y.z   # but this is a comment
-.endd
-.endlist
-
-Putting a filename in a list has the same effect as inserting each line of the
-file as an item in the list (blank lines and comments excepted). However, there
-is one important difference: the file is read each time the list is processed,
-so if its contents vary over time, Exim's behaviour changes.
-
-If a filename is preceded by an exclamation mark, the sense of any match
-within the file is inverted. For example, if
-.code
-hold_domains = !/etc/nohold-domains
-.endd
-and the file contains the lines
-.code
-!a.b.c
-*.b.c
-.endd
-then &'a.b.c'& is in the set of domains defined by &%hold_domains%&, whereas
-any domain matching &`*.b.c`& is not.
-
-
-
-.section "An lsearch file is not an out-of-line list" "SECID77"
-As will be described in the sections that follow, lookups can be used in lists
-to provide indexed methods of checking list membership. There has been some
-confusion about the way &(lsearch)& lookups work in lists. Because
-an &(lsearch)& file contains plain text and is scanned sequentially, it is
-sometimes thought that it is allowed to contain wild cards and other kinds of
-non-constant pattern. This is not the case. The keys in an &(lsearch)& file are
-always fixed strings, just as for any other single-key lookup type.
-
-If you want to use a file to contain wild-card patterns that form part of a
-list, just give the filename on its own, without a search type, as described
-in the previous section. You could also use the &(wildlsearch)& or
-&(nwildlsearch)&, but there is no advantage in doing this.
-
-
-
-
-.section "Named lists" "SECTnamedlists"
-.cindex "named lists"
-.cindex "list" "named"
-A list of domains, hosts, email addresses, or local parts can be given a name
-which is then used to refer to the list elsewhere in the configuration. This is
-particularly convenient if the same list is required in several different
-places. It also allows lists to be given meaningful names, which can improve
-the readability of the configuration. For example, it is conventional to define
-a domain list called &'local_domains'& for all the domains that are handled
-locally on a host, using a configuration line such as
-.code
-domainlist local_domains = localhost:my.dom.example
-.endd
-Named lists are referenced by giving their name preceded by a plus sign, so,
-for example, a router that is intended to handle local domains would be
-configured with the line
-.code
-domains = +local_domains
-.endd
-The first router in a configuration is often one that handles all domains
-except the local ones, using a configuration with a negated item like this:
-.code
-dnslookup:
-  driver = dnslookup
-  domains = ! +local_domains
-  transport = remote_smtp
-  no_more
-.endd
-The four kinds of named list are created by configuration lines starting with
-the words &%domainlist%&, &%hostlist%&, &%addresslist%&, or &%localpartlist%&,
-respectively. Then there follows the name that you are defining, followed by an
-equals sign and the list itself. For example:
-.code
-hostlist    relay_from_hosts = 192.168.23.0/24 : my.friend.example
-addresslist bad_senders = cdb;/etc/badsenders
-.endd
-A named list may refer to other named lists:
-.code
-domainlist  dom1 = first.example : second.example
-domainlist  dom2 = +dom1 : third.example
-domainlist  dom3 = fourth.example : +dom2 : fifth.example
-.endd
-&*Warning*&: If the last item in a referenced list is a negative one, the
-effect may not be what you intended, because the negation does not propagate
-out to the higher level. For example, consider:
-.code
-domainlist  dom1 = !a.b
-domainlist  dom2 = +dom1 : *.b
-.endd
-The second list specifies &"either in the &%dom1%& list or &'*.b'&"&. The first
-list specifies just &"not &'a.b'&"&, so the domain &'x.y'& matches it. That
-means it matches the second list as well. The effect is not the same as
-.code
-domainlist  dom2 = !a.b : *.b
-.endd
-where &'x.y'& does not match. It's best to avoid negation altogether in
-referenced lists if you can.
-
-.new
-.cindex "hiding named list values"
-.cindex "named lists" "hiding value of"
-Some named list definitions may contain sensitive data, for example, passwords for
-accessing databases. To stop non-admin users from using the &%-bP%& command
-line option to read these values, you can precede the definition with the
-word &"hide"&. For example:
-.code
-hide domainlist filter_for_domains = ldap;PASS=secret ldap::/// ...
-.endd
-.wen
-
-
-Named lists may have a performance advantage. When Exim is routing an
-address or checking an incoming message, it caches the result of tests on named
-lists. So, if you have a setting such as
-.code
-domains = +local_domains
-.endd
-on several of your routers
-or in several ACL statements,
-the actual test is done only for the first one. However, the caching works only
-if there are no expansions within the list itself or any sublists that it
-references. In other words, caching happens only for lists that are known to be
-the same each time they are referenced.
-
-By default, there may be up to 16 named lists of each type. This limit can be
-extended by changing a compile-time variable. The use of domain and host lists
-is recommended for concepts such as local domains, relay domains, and relay
-hosts. The default configuration is set up like this.
-
-
-
-.section "Named lists compared with macros" "SECID78"
-.cindex "list" "named compared with macro"
-.cindex "macro" "compared with named list"
-At first sight, named lists might seem to be no different from macros in the
-configuration file. However, macros are just textual substitutions. If you
-write
-.code
-ALIST = host1 : host2
-auth_advertise_hosts = !ALIST
-.endd
-it probably won't do what you want, because that is exactly the same as
-.code
-auth_advertise_hosts = !host1 : host2
-.endd
-Notice that the second host name is not negated. However, if you use a host
-list, and write
-.code
-hostlist alist = host1 : host2
-auth_advertise_hosts = ! +alist
-.endd
-the negation applies to the whole list, and so that is equivalent to
-.code
-auth_advertise_hosts = !host1 : !host2
-.endd
-
-
-.section "Named list caching" "SECID79"
-.cindex "list" "caching of named"
-.cindex "caching" "named lists"
-While processing a message, Exim caches the result of checking a named list if
-it is sure that the list is the same each time. In practice, this means that
-the cache operates only if the list contains no $ characters, which guarantees
-that it will not change when it is expanded. Sometimes, however, you may have
-an expanded list that you know will be the same each time within a given
-message. For example:
-.code
-domainlist special_domains = \
-           ${lookup{$sender_host_address}cdb{/some/file}}
-.endd
-This provides a list of domains that depends only on the sending host's IP
-address. If this domain list is referenced a number of times (for example,
-in several ACL lines, or in several routers) the result of the check is not
-cached by default, because Exim does not know that it is going to be the
-same list each time.
-
-By appending &`_cache`& to &`domainlist`& you can tell Exim to go ahead and
-cache the result anyway. For example:
-.code
-domainlist_cache special_domains = ${lookup{...
-.endd
-If you do this, you should be absolutely sure that caching is going to do
-the right thing in all cases. When in doubt, leave it out.
-
-
-
-.section "Domain lists" "SECTdomainlist"
-.cindex "domain list" "patterns for"
-.cindex "list" "domain list"
-Domain lists contain patterns that are to be matched against a mail domain.
-The following types of item may appear in domain lists:
-
-.ilist
-.cindex "primary host name"
-.cindex "host name" "matched in domain list"
-.oindex "&%primary_hostname%&"
-.cindex "domain list" "matching primary host name"
-.cindex "@ in a domain list"
-If a pattern consists of a single @ character, it matches the local host name,
-as set by the &%primary_hostname%& option (or defaulted). This makes it
-possible to use the same configuration file on several different hosts that
-differ only in their names.
-.next
-.cindex "@[] in a domain list"
-.cindex "domain list" "matching local IP interfaces"
-.cindex "domain literal"
-If a pattern consists of the string &`@[]`& it matches an IP address enclosed
-in square brackets (as in an email address that contains a domain literal), but
-only if that IP address is recognized as local for email routing purposes. The
-&%local_interfaces%& and &%extra_local_interfaces%& options can be used to
-control which of a host's several IP addresses are treated as local.
-In today's Internet, the use of domain literals is controversial.
-.next
-.cindex "@mx_any"
-.cindex "@mx_primary"
-.cindex "@mx_secondary"
-.cindex "domain list" "matching MX pointers to local host"
-If a pattern consists of the string &`@mx_any`& it matches any domain that
-has an MX record pointing to the local host or to any host that is listed in
-.oindex "&%hosts_treat_as_local%&"
-&%hosts_treat_as_local%&. The items &`@mx_primary`& and &`@mx_secondary`&
-are similar, except that the first matches only when a primary MX target is the
-local host, and the second only when no primary MX target is the local host,
-but a secondary MX target is. &"Primary"& means an MX record with the lowest
-preference value &-- there may of course be more than one of them.
-
-The MX lookup that takes place when matching a pattern of this type is
-performed with the resolver options for widening names turned off. Thus, for
-example, a single-component domain will &'not'& be expanded by adding the
-resolver's default domain. See the &%qualify_single%& and &%search_parents%&
-options of the &(dnslookup)& router for a discussion of domain widening.
-
-Sometimes you may want to ignore certain IP addresses when using one of these
-patterns. You can specify this by following the pattern with &`/ignore=`&<&'ip
-list'&>, where <&'ip list'&> is a list of IP addresses. These addresses are
-ignored when processing the pattern (compare the &%ignore_target_hosts%& option
-on a router). For example:
-.code
-domains = @mx_any/ignore=127.0.0.1
-.endd
-This example matches any domain that has an MX record pointing to one of
-the local host's IP addresses other than 127.0.0.1.
-
-The list of IP addresses is in fact processed by the same code that processes
-host lists, so it may contain CIDR-coded network specifications and it may also
-contain negative items.
-
-Because the list of IP addresses is a sublist within a domain list, you have to
-be careful about delimiters if there is more than one address. Like any other
-list, the default delimiter can be changed. Thus, you might have:
-.code
-domains = @mx_any/ignore=<;127.0.0.1;0.0.0.0 : \
-          an.other.domain : ...
-.endd
-so that the sublist uses semicolons for delimiters. When IPv6 addresses are
-involved, it is easiest to change the delimiter for the main list as well:
-.code
-domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
-          an.other.domain ? ...
-.endd
-.next
-.cindex "asterisk" "in domain list"
-.cindex "domain list" "asterisk in"
-.cindex "domain list" "matching &""ends with""&"
-If a pattern starts with an asterisk, the remaining characters of the pattern
-are compared with the terminating characters of the domain. The use of &"*"& in
-domain lists differs from its use in partial matching lookups. In a domain
-list, the character following the asterisk need not be a dot, whereas partial
-matching works only in terms of dot-separated components. For example, a domain
-list item such as &`*key.ex`& matches &'donkey.ex'& as well as
-&'cipher.key.ex'&.
-
-.next
-.cindex "regular expressions" "in domain list"
-.cindex "domain list" "matching regular expression"
-If a pattern starts with a circumflex character, it is treated as a regular
-expression, and matched against the domain using a regular expression matching
-function. The circumflex is treated as part of the regular expression.
-Email domains are case-independent, so this regular expression match is by
-default case-independent, but you can make it case-dependent by starting it
-with &`(?-i)`&. References to descriptions of the syntax of regular expressions
-are given in chapter &<<CHAPregexp>>&.
-
-&*Warning*&: Because domain lists are expanded before being processed, you
-must escape any backslash and dollar characters in the regular expression, or
-use the special &`\N`& sequence (see chapter &<<CHAPexpand>>&) to specify that
-it is not to be expanded (unless you really do want to build a regular
-expression by expansion, of course).
-.next
-.cindex "lookup" "in domain list"
-.cindex "domain list" "matching by lookup"
-If a pattern starts with the name of a single-key lookup type followed by a
-semicolon (for example, &"dbm;"& or &"lsearch;"&), the remainder of the pattern
-must be a filename in a suitable format for the lookup type. For example, for
-&"cdb;"& it must be an absolute path:
-.code
-domains = cdb;/etc/mail/local_domains.cdb
-.endd
-The appropriate type of lookup is done on the file using the domain name as the
-key. In most cases, the data that is looked up is not used; Exim is interested
-only in whether or not the key is present in the file. However, when a lookup
-is used for the &%domains%& option on a router
-or a &%domains%& condition in an ACL statement, the data is preserved in the
-&$domain_data$& variable and can be referred to in other router options or
-other statements in the same ACL.
-
-.next
-Any of the single-key lookup type names may be preceded by
-&`partial`&<&'n'&>&`-`&, where the <&'n'&> is optional, for example,
-.code
-domains = partial-dbm;/partial/domains
-.endd
-This causes partial matching logic to be invoked; a description of how this
-works is given in section &<<SECTpartiallookup>>&.
-
-.next
-.cindex "asterisk" "in lookup type"
-Any of the single-key lookup types may be followed by an asterisk. This causes
-a default lookup for a key consisting of a single asterisk to be done if the
-original lookup fails. This is not a useful feature when using a domain list to
-select particular domains (because any domain would match), but it might have
-value if the result of the lookup is being used via the &$domain_data$&
-expansion variable.
-.next
-If the pattern starts with the name of a query-style lookup type followed by a
-semicolon (for example, &"nisplus;"& or &"ldap;"&), the remainder of the
-pattern must be an appropriate query for the lookup type, as described in
-chapter &<<CHAPfdlookup>>&. For example:
-.code
-hold_domains = mysql;select domain from holdlist \
-  where domain = '${quote_mysql:$domain}';
-.endd
-In most cases, the data that is looked up is not used (so for an SQL query, for
-example, it doesn't matter what field you select). Exim is interested only in
-whether or not the query succeeds. However, when a lookup is used for the
-&%domains%& option on a router, the data is preserved in the &$domain_data$&
-variable and can be referred to in other options.
-.next
-.new
-If the pattern starts with the name of a lookup type
-of either kind (single-key or query-style) it may be
-followed by a command and options,
-The options are lookup-type specific and consist of a comma-separated list.
-Each item starts with a tag and and equals "=".
-.wen
-.next
-.cindex "domain list" "matching literal domain name"
-If none of the above cases apply, a caseless textual comparison is made
-between the pattern and the domain.
-.endlist
-
-Here is an example that uses several different kinds of pattern:
-.code
-domainlist funny_domains = \
-  @ : \
-  lib.unseen.edu : \
-  *.foundation.fict.example : \
-  \N^[1-2]\d{3}\.fict\.example$\N : \
-  partial-dbm;/opt/data/penguin/book : \
-  nis;domains.byname : \
-  nisplus;[name=$domain,status=local],domains.org_dir
-.endd
-There are obvious processing trade-offs among the various matching modes. Using
-an asterisk is faster than a regular expression, and listing a few names
-explicitly probably is too. The use of a file or database lookup is expensive,
-but may be the only option if hundreds of names are required. Because the
-patterns are tested in order, it makes sense to put the most commonly matched
-patterns earlier.
-
-
-
-.section "Host lists" "SECThostlist"
-.cindex "host list" "patterns in"
-.cindex "list" "host list"
-Host lists are used to control what remote hosts are allowed to do. For
-example, some hosts may be allowed to use the local host as a relay, and some
-may be permitted to use the SMTP ETRN command. Hosts can be identified in
-two different ways, by name or by IP address. In a host list, some types of
-pattern are matched to a host name, and some are matched to an IP address.
-You need to be particularly careful with this when single-key lookups are
-involved, to ensure that the right value is being used as the key.
-
-
-.section "Special host list patterns" "SECID80"
-.cindex "empty item in hosts list"
-.cindex "host list" "empty string in"
-If a host list item is the empty string, it matches only when no remote host is
-involved. This is the case when a message is being received from a local
-process using SMTP on the standard input, that is, when a TCP/IP connection is
-not used.
-
-.cindex "asterisk" "in host list"
-The special pattern &"*"& in a host list matches any host or no host. Neither
-the IP address nor the name is actually inspected.
-
-
-
-.section "Host list patterns that match by IP address" "SECThoslispatip"
-.cindex "host list" "matching IP addresses"
-If an IPv4 host calls an IPv6 host and the call is accepted on an IPv6 socket,
-the incoming address actually appears in the IPv6 host as
-&`::ffff:`&<&'v4address'&>. When such an address is tested against a host
-list, it is converted into a traditional IPv4 address first. (Not all operating
-systems accept IPv4 calls on IPv6 sockets, as there have been some security
-concerns.)
-
-The following types of pattern in a host list check the remote host by
-inspecting its IP address:
-
-.ilist
-If the pattern is a plain domain name (not a regular expression, not starting
-with *, not a lookup of any kind), Exim calls the operating system function
-to find the associated IP address(es). Exim uses the newer
-&[getipnodebyname()]& function when available, otherwise &[gethostbyname()]&.
-This typically causes a forward DNS lookup of the name. The result is compared
-with the IP address of the subject host.
-
-If there is a temporary problem (such as a DNS timeout) with the host name
-lookup, a temporary error occurs. For example, if the list is being used in an
-ACL condition, the ACL gives a &"defer"& response, usually leading to a
-temporary SMTP error code. If no IP address can be found for the host name,
-what happens is described in section &<<SECTbehipnot>>& below.
-
-.next
-.cindex "@ in a host list"
-If the pattern is &"@"&, the primary host name is substituted and used as a
-domain name, as just described.
-
-.next
-If the pattern is an IP address, it is matched against the IP address of the
-subject host. IPv4 addresses are given in the normal &"dotted-quad"& notation.
-IPv6 addresses can be given in colon-separated format, but the colons have to
-be doubled so as not to be taken as item separators when the default list
-separator is used. IPv6 addresses are recognized even when Exim is compiled
-without IPv6 support. This means that if they appear in a host list on an
-IPv4-only host, Exim will not treat them as host names. They are just addresses
-that can never match a client host.
-
-.next
-.cindex "@[] in a host list"
-If the pattern is &"@[]"&, it matches the IP address of any IP interface on
-the local host. For example, if the local host is an IPv4 host with one
-interface address 10.45.23.56, these two ACL statements have the same effect:
-.code
-accept hosts = 127.0.0.1 : 10.45.23.56
-accept hosts = @[]
-.endd
-.next
-.cindex "CIDR notation"
-If the pattern is an IP address followed by a slash and a mask length (for
-example 10.11.42.0/24), it is matched against the IP address of the subject
-host under the given mask. This allows, an entire network of hosts to be
-included (or excluded) by a single item. The mask uses CIDR notation; it
-specifies the number of address bits that must match, starting from the most
-significant end of the address.
-
-&*Note*&: The mask is &'not'& a count of addresses, nor is it the high number
-of a range of addresses. It is the number of bits in the network portion of the
-address. The above example specifies a 24-bit netmask, so it matches all 256
-addresses in the 10.11.42.0 network. An item such as
-.code
-192.168.23.236/31
-.endd
-matches just two addresses, 192.168.23.236 and 192.168.23.237. A mask value of
-32 for an IPv4 address is the same as no mask at all; just a single address
-matches.
-
-Here is another example which shows an IPv4 and an IPv6 network:
-.code
-recipient_unqualified_hosts = 192.168.0.0/16: \
-                              3ffe::ffff::836f::::/48
-.endd
-The doubling of list separator characters applies only when these items
-appear inline in a host list. It is not required when indirecting via a file.
-For example:
-.code
-recipient_unqualified_hosts = /opt/exim/unqualnets
-.endd
-could make use of a file containing
-.code
-172.16.0.0/12
-3ffe:ffff:836f::/48
-.endd
-to have exactly the same effect as the previous example. When listing IPv6
-addresses inline, it is usually more convenient to use the facility for
-changing separator characters. This list contains the same two networks:
-.code
-recipient_unqualified_hosts = <; 172.16.0.0/12; \
-                                 3ffe:ffff:836f::/48
-.endd
-The separator is changed to semicolon by the leading &"<;"& at the start of the
-list.
-.endlist
-
-
-
-.section "Host list patterns for single-key lookups by host address" &&&
-         "SECThoslispatsikey"
-.cindex "host list" "lookup of IP address"
-When a host is to be identified by a single-key lookup of its complete IP
-address, the pattern takes this form:
-.display
-&`net-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
-.endd
-For example:
-.code
-hosts_lookup = net-cdb;/hosts-by-ip.db
-.endd
-The text form of the IP address of the subject host is used as the lookup key.
-IPv6 addresses are converted to an unabbreviated form, using lower case
-letters, with dots as separators because colon is the key terminator in
-&(lsearch)& files. [Colons can in fact be used in keys in &(lsearch)& files by
-quoting the keys, but this is a facility that was added later.] The data
-returned by the lookup is not used.
-
-.cindex "IP address" "masking"
-.cindex "host list" "masked IP address"
-Single-key lookups can also be performed using masked IP addresses, using
-patterns of this form:
-.display
-&`net<`&&'number'&&`>-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
-.endd
-For example:
-.code
-net24-dbm;/networks.db
-.endd
-The IP address of the subject host is masked using <&'number'&> as the mask
-length. A textual string is constructed from the masked value, followed by the
-mask, and this is used as the lookup key. For example, if the host's IP address
-is 192.168.34.6, the key that is looked up for the above example is
-&"192.168.34.0/24"&.
-
-When an IPv6 address is converted to a string, dots are normally used instead
-of colons, so that keys in &(lsearch)& files need not contain colons (which
-terminate &(lsearch)& keys). This was implemented some time before the ability
-to quote keys was made available in &(lsearch)& files. However, the more
-recently implemented &(iplsearch)& files do require colons in IPv6 keys
-(notated using the quoting facility) so as to distinguish them from IPv4 keys.
-For this reason, when the lookup type is &(iplsearch)&, IPv6 addresses are
-converted using colons and not dots.
-In all cases except IPv4-mapped IPv6, full, unabbreviated IPv6
-addresses are always used.
-The latter are converted to IPv4 addresses, in dotted-quad form.
-
-Ideally, it would be nice to tidy up this anomalous situation by changing to
-colons in all cases, given that quoting is now available for &(lsearch)&.
-However, this would be an incompatible change that might break some existing
-configurations.
-
-&*Warning*&: Specifying &%net32-%& (for an IPv4 address) or &%net128-%& (for an
-IPv6 address) is not the same as specifying just &%net-%& without a number. In
-the former case the key strings include the mask value, whereas in the latter
-case the IP address is used on its own.
-
-
-
-.section "Host list patterns that match by host name" "SECThoslispatnam"
-.cindex "host" "lookup failures"
-.cindex "unknown host name"
-.cindex "host list" "matching host name"
-There are several types of pattern that require Exim to know the name of the
-remote host. These are either wildcard patterns or lookups by name. (If a
-complete hostname is given without any wildcarding, it is used to find an IP
-address to match against, as described in section &<<SECThoslispatip>>&
-above.)
-
-If the remote host name is not already known when Exim encounters one of these
-patterns, it has to be found from the IP address.
-Although many sites on the Internet are conscientious about maintaining reverse
-DNS data for their hosts, there are also many that do not do this.
-Consequently, a name cannot always be found, and this may lead to unwanted
-effects. Take care when configuring host lists with wildcarded name patterns.
-Consider what will happen if a name cannot be found.
-
-Because of the problems of determining host names from IP addresses, matching
-against host names is not as common as matching against IP addresses.
-
-By default, in order to find a host name, Exim first does a reverse DNS lookup;
-if no name is found in the DNS, the system function (&[gethostbyaddr()]& or
-&[getipnodebyaddr()]& if available) is tried. The order in which these lookups
-are done can be changed by setting the &%host_lookup_order%& option. For
-security, once Exim has found one or more names, it looks up the IP addresses
-for these names and compares them with the IP address that it started with.
-Only those names whose IP addresses match are accepted. Any other names are
-discarded. If no names are left, Exim behaves as if the host name cannot be
-found. In the most common case there is only one name and one IP address.
-
-There are some options that control what happens if a host name cannot be
-found. These are described in section &<<SECTbehipnot>>& below.
-
-.cindex "host" "alias for"
-.cindex "alias for host"
-As a result of aliasing, hosts may have more than one name. When processing any
-of the following types of pattern, all the host's names are checked:
-
-.ilist
-.cindex "asterisk" "in host list"
-If a pattern starts with &"*"& the remainder of the item must match the end of
-the host name. For example, &`*.b.c`& matches all hosts whose names end in
-&'.b.c'&. This special simple form is provided because this is a very common
-requirement. Other kinds of wildcarding require the use of a regular
-expression.
-.next
-.cindex "regular expressions" "in host list"
-.cindex "host list" "regular expression in"
-If the item starts with &"^"& it is taken to be a regular expression which is
-matched against the host name. Host names are case-independent, so this regular
-expression match is by default case-independent, but you can make it
-case-dependent by starting it with &`(?-i)`&. References to descriptions of the
-syntax of regular expressions are given in chapter &<<CHAPregexp>>&. For
-example,
-.code
-^(a|b)\.c\.d$
-.endd
-is a regular expression that matches either of the two hosts &'a.c.d'& or
-&'b.c.d'&. When a regular expression is used in a host list, you must take care
-that backslash and dollar characters are not misinterpreted as part of the
-string expansion. The simplest way to do this is to use &`\N`& to mark that
-part of the string as non-expandable. For example:
-.code
-sender_unqualified_hosts = \N^(a|b)\.c\.d$\N : ....
-.endd
-&*Warning*&: If you want to match a complete host name, you must include the
-&`$`& terminating metacharacter in the regular expression, as in the above
-example. Without it, a match at the start of the host name is all that is
-required.
-.endlist
-
-
-
-
-.section "Behaviour when an IP address or name cannot be found" "SECTbehipnot"
-.cindex "host" "lookup failures, permanent"
-While processing a host list, Exim may need to look up an IP address from a
-name (see section &<<SECThoslispatip>>&), or it may need to look up a host name
-from an IP address (see section &<<SECThoslispatnam>>&). In either case, the
-behaviour when it fails to find the information it is seeking is the same.
-
-&*Note*&: This section applies to permanent lookup failures. It does &'not'&
-apply to temporary DNS errors, whose handling is described in the next section.
-
-.cindex "&`+include_unknown`&"
-.cindex "&`+ignore_unknown`&"
-Exim parses a host list from left to right. If it encounters a permanent
-lookup failure in any item in the host list before it has found a match,
-Exim treats it as a failure and the default behavior is as if the host
-does not match the list. This may not always be what you want to happen.
-To change Exim's behaviour, the special items &`+include_unknown`& or
-&`+ignore_unknown`& may appear in the list (at top level &-- they are
-not recognized in an indirected file).
-
-.ilist
-If any item that follows &`+include_unknown`& requires information that
-cannot found, Exim behaves as if the host does match the list. For example,
-.code
-host_reject_connection = +include_unknown:*.enemy.ex
-.endd
-rejects connections from any host whose name matches &`*.enemy.ex`&, and also
-any hosts whose name it cannot find.
-
-.next
-If any item that follows &`+ignore_unknown`& requires information that cannot
-be found, Exim ignores that item and proceeds to the rest of the list. For
-example:
-.code
-accept hosts = +ignore_unknown : friend.example : \
-               192.168.4.5
-.endd
-accepts from any host whose name is &'friend.example'& and from 192.168.4.5,
-whether or not its host name can be found. Without &`+ignore_unknown`&, if no
-name can be found for 192.168.4.5, it is rejected.
-.endlist
-
-Both &`+include_unknown`& and &`+ignore_unknown`& may appear in the same
-list. The effect of each one lasts until the next, or until the end of the
-list.
-
-.section "Mixing wildcarded host names and addresses in host lists" &&&
-         "SECTmixwilhos"
-.cindex "host list" "mixing names and addresses in"
-
-This section explains the host/ip processing logic with the same concepts
-as the previous section, but specifically addresses what happens when a
-wildcarded hostname is one of the items in the hostlist.
-
-.ilist
-If you have name lookups or wildcarded host names and
-IP addresses in the same host list, you should normally put the IP
-addresses first. For example, in an ACL you could have:
-.code
-accept hosts = 10.9.8.7 : *.friend.example
-.endd
-The reason you normally would order it this way lies in the
-left-to-right way that Exim processes lists.  It can test IP addresses
-without doing any DNS lookups, but when it reaches an item that requires
-a host name, it fails if it cannot find a host name to compare with the
-pattern. If the above list is given in the opposite order, the
-&%accept%& statement fails for a host whose name cannot be found, even
-if its IP address is 10.9.8.7.
-
-.next
-If you really do want to do the name check first, and still recognize the IP
-address, you can rewrite the ACL like this:
-.code
-accept hosts = *.friend.example
-accept hosts = 10.9.8.7
-.endd
-If the first &%accept%& fails, Exim goes on to try the second one. See chapter
-&<<CHAPACL>>& for details of ACLs. Alternatively, you can use
-&`+ignore_unknown`&, which was discussed in depth in the first example in
-this section.
-.endlist
-
-
-.section "Temporary DNS errors when looking up host information" &&&
-         "SECTtemdnserr"
-.cindex "host" "lookup failures, temporary"
-.cindex "&`+include_defer`&"
-.cindex "&`+ignore_defer`&"
-A temporary DNS lookup failure normally causes a defer action (except when
-&%dns_again_means_nonexist%& converts it into a permanent error). However,
-host lists can include &`+ignore_defer`& and &`+include_defer`&, analogous to
-&`+ignore_unknown`& and &`+include_unknown`&, as described in the previous
-section. These options should be used with care, probably only in non-critical
-host lists such as whitelists.
-
-
-
-.section "Host list patterns for single-key lookups by host name" &&&
-         "SECThoslispatnamsk"
-.cindex "unknown host name"
-.cindex "host list" "matching host name"
-If a pattern is of the form
-.display
-<&'single-key-search-type'&>;<&'search-data'&>
-.endd
-for example
-.code
-dbm;/host/accept/list
-.endd
-a single-key lookup is performed, using the host name as its key. If the
-lookup succeeds, the host matches the item. The actual data that is looked up
-is not used.
-
-&*Reminder*&: With this kind of pattern, you must have host &'names'& as
-keys in the file, not IP addresses. If you want to do lookups based on IP
-addresses, you must precede the search type with &"net-"& (see section
-&<<SECThoslispatsikey>>&). There is, however, no reason why you could not use
-two items in the same list, one doing an address lookup and one doing a name
-lookup, both using the same file.
-
-
-
-.section "Host list patterns for query-style lookups" "SECID81"
-If a pattern is of the form
-.display
-<&'query-style-search-type'&>;<&'query'&>
-.endd
-the query is obeyed, and if it succeeds, the host matches the item. The actual
-data that is looked up is not used. The variables &$sender_host_address$& and
-&$sender_host_name$& can be used in the query. For example:
-.code
-hosts_lookup = pgsql;\
-  select ip from hostlist where ip='$sender_host_address'
-.endd
-The value of &$sender_host_address$& for an IPv6 address contains colons. You
-can use the &%sg%& expansion item to change this if you need to. If you want to
-use masked IP addresses in database queries, you can use the &%mask%& expansion
-operator.
-
-If the query contains a reference to &$sender_host_name$&, Exim automatically
-looks up the host name if it has not already done so. (See section
-&<<SECThoslispatnam>>& for comments on finding host names.)
-
-Historical note: prior to release 4.30, Exim would always attempt to find a
-host name before running the query, unless the search type was preceded by
-&`net-`&. This is no longer the case. For backwards compatibility, &`net-`& is
-still recognized for query-style lookups, but its presence or absence has no
-effect. (Of course, for single-key lookups, &`net-`& &'is'& important.
-See section &<<SECThoslispatsikey>>&.)
-
-
-
-
-
-.section "Address lists" "SECTaddresslist"
-.cindex "list" "address list"
-.cindex "address list" "empty item"
-.cindex "address list" "patterns"
-Address lists contain patterns that are matched against mail addresses. There
-is one special case to be considered: the sender address of a bounce message is
-always empty. You can test for this by providing an empty item in an address
-list. For example, you can set up a router to process bounce messages by
-using this option setting:
-.code
-senders = :
-.endd
-The presence of the colon creates an empty item. If you do not provide any
-data, the list is empty and matches nothing. The empty sender can also be
-detected by a regular expression that matches an empty string,
-and by a query-style lookup that succeeds when &$sender_address$& is empty.
-
-Non-empty items in an address list can be straightforward email addresses. For
-example:
-.code
-senders = jbc@askone.example : hs@anacreon.example
-.endd
-A certain amount of wildcarding is permitted. If a pattern contains an @
-character, but is not a regular expression and does not begin with a
-semicolon-terminated lookup type (described below), the local part of the
-subject address is compared with the local part of the pattern, which may start
-with an asterisk. If the local parts match, the domain is checked in exactly
-the same way as for a pattern in a domain list. For example, the domain can be
-wildcarded, refer to a named list, or be a lookup:
-.code
-deny senders = *@*.spamming.site:\
-               *@+hostile_domains:\
-               bozo@partial-lsearch;/list/of/dodgy/sites:\
-               *@dbm;/bad/domains.db
-.endd
-.cindex "local part" "starting with !"
-.cindex "address list" "local part starting with !"
-If a local part that begins with an exclamation mark is required, it has to be
-specified using a regular expression, because otherwise the exclamation mark is
-treated as a sign of negation, as is standard in lists.
-
-If a non-empty pattern that is not a regular expression or a lookup does not
-contain an @ character, it is matched against the domain part of the subject
-address. The only two formats that are recognized this way are a literal
-domain, or a domain pattern that starts with *. In both these cases, the effect
-is the same as if &`*@`& preceded the pattern. For example:
-.code
-deny senders = enemy.domain : *.enemy.domain
-.endd
-
-The following kinds of more complicated address list pattern can match any
-address, including the empty address that is characteristic of bounce message
-senders:
-
-.ilist
-.cindex "regular expressions" "in address list"
-.cindex "address list" "regular expression in"
-If (after expansion) a pattern starts with &"^"&, a regular expression match is
-done against the complete address, with the pattern as the regular expression.
-You must take care that backslash and dollar characters are not misinterpreted
-as part of the string expansion. The simplest way to do this is to use &`\N`&
-to mark that part of the string as non-expandable. For example:
-.code
-deny senders = \N^.*this.*@example\.com$\N : \
-               \N^\d{8}.+@spamhaus.example$\N : ...
-.endd
-The &`\N`& sequences are removed by the expansion, so these items do indeed
-start with &"^"& by the time they are being interpreted as address patterns.
-
-.next
-.cindex "address list" "lookup for complete address"
-Complete addresses can be looked up by using a pattern that starts with a
-lookup type terminated by a semicolon, followed by the data for the lookup. For
-example:
-.code
-deny senders = cdb;/etc/blocked.senders : \
-  mysql;select address from blocked where \
-  address='${quote_mysql:$sender_address}'
-.endd
-Both query-style and single-key lookup types can be used. For a single-key
-lookup type, Exim uses the complete address as the key. However, empty keys are
-not supported for single-key lookups, so a match against the empty address
-always fails. This restriction does not apply to query-style lookups.
-
-Partial matching for single-key lookups (section &<<SECTpartiallookup>>&)
-cannot be used, and is ignored if specified, with an entry being written to the
-panic log.
-.cindex "*@ with single-key lookup"
-However, you can configure lookup defaults, as described in section
-&<<SECTdefaultvaluelookups>>&, but this is useful only for the &"*@"& type of
-default. For example, with this lookup:
-.code
-accept senders = lsearch*@;/some/file
-.endd
-the file could contains lines like this:
-.code
-user1@domain1.example
-*@domain2.example
-.endd
-and for the sender address &'nimrod@jaeger.example'&, the sequence of keys
-that are tried is:
-.code
-nimrod@jaeger.example
-*@jaeger.example
-*
-.endd
-&*Warning 1*&: Do not include a line keyed by &"*"& in the file, because that
-would mean that every address matches, thus rendering the test useless.
-
-&*Warning 2*&: Do not confuse these two kinds of item:
-.code
-deny recipients = dbm*@;/some/file
-deny recipients = *@dbm;/some/file
-.endd
-The first does a whole address lookup, with defaulting, as just described,
-because it starts with a lookup type. The second matches the local part and
-domain independently, as described in a bullet point below.
-.endlist
-
-
-The following kinds of address list pattern can match only non-empty addresses.
-If the subject address is empty, a match against any of these pattern types
-always fails.
-
-
-.ilist
-.cindex "@@ with single-key lookup"
-.cindex "address list" "@@ lookup type"
-.cindex "address list" "split local part and domain"
-If a pattern starts with &"@@"& followed by a single-key lookup item
-(for example, &`@@lsearch;/some/file`&), the address that is being checked is
-split into a local part and a domain. The domain is looked up in the file. If
-it is not found, there is no match. If it is found, the data that is looked up
-from the file is treated as a colon-separated list of local part patterns, each
-of which is matched against the subject local part in turn.
-
-.cindex "asterisk" "in address list"
-The lookup may be a partial one, and/or one involving a search for a default
-keyed by &"*"& (see section &<<SECTdefaultvaluelookups>>&). The local part
-patterns that are looked up can be regular expressions or begin with &"*"&, or
-even be further lookups. They may also be independently negated. For example,
-with
-.code
-deny senders = @@dbm;/etc/reject-by-domain
-.endd
-the data from which the DBM file is built could contain lines like
-.code
-baddomain.com:  !postmaster : *
-.endd
-to reject all senders except &%postmaster%& from that domain.
-
-.cindex "local part" "starting with !"
-If a local part that actually begins with an exclamation mark is required, it
-has to be specified using a regular expression. In &(lsearch)& files, an entry
-may be split over several lines by indenting the second and subsequent lines,
-but the separating colon must still be included at line breaks. White space
-surrounding the colons is ignored. For example:
-.code
-aol.com:  spammer1 : spammer2 : ^[0-9]+$ :
-  spammer3 : spammer4
-.endd
-As in all colon-separated lists in Exim, a colon can be included in an item by
-doubling.
-
-If the last item in the list starts with a right angle-bracket, the remainder
-of the item is taken as a new key to look up in order to obtain a continuation
-list of local parts. The new key can be any sequence of characters. Thus one
-might have entries like
-.code
-aol.com: spammer1 : spammer 2 : >*
-xyz.com: spammer3 : >*
-*:       ^\d{8}$
-.endd
-in a file that was searched with &%@@dbm*%&, to specify a match for 8-digit
-local parts for all domains, in addition to the specific local parts listed for
-each domain. Of course, using this feature costs another lookup each time a
-chain is followed, but the effort needed to maintain the data is reduced.
-
-.cindex "loop" "in lookups"
-It is possible to construct loops using this facility, and in order to catch
-them, the chains may be no more than fifty items long.
-
-.next
-The @@<&'lookup'&> style of item can also be used with a query-style
-lookup, but in this case, the chaining facility is not available. The lookup
-can only return a single list of local parts.
-.endlist
-
-&*Warning*&: There is an important difference between the address list items
-in these two examples:
-.code
-senders = +my_list
-senders = *@+my_list
-.endd
-In the first one, &`my_list`& is a named address list, whereas in the second
-example it is a named domain list.
-
-
-
-
-.section "Case of letters in address lists" "SECTcasletadd"
-.cindex "case of local parts"
-.cindex "address list" "case forcing"
-.cindex "case forcing in address lists"
-Domains in email addresses are always handled caselessly, but for local parts
-case may be significant on some systems (see &%caseful_local_part%& for how
-Exim deals with this when routing addresses). However, RFC 2505 (&'Anti-Spam
-Recommendations for SMTP MTAs'&) suggests that matching of addresses to
-blocking lists should be done in a case-independent manner. Since most address
-lists in Exim are used for this kind of control, Exim attempts to do this by
-default.
-
-The domain portion of an address is always lowercased before matching it to an
-address list. The local part is lowercased by default, and any string
-comparisons that take place are done caselessly. This means that the data in
-the address list itself, in files included as plain filenames, and in any file
-that is looked up using the &"@@"& mechanism, can be in any case. However, the
-keys in files that are looked up by a search type other than &(lsearch)& (which
-works caselessly) must be in lower case, because these lookups are not
-case-independent.
-
-.cindex "&`+caseful`&"
-To allow for the possibility of caseful address list matching, if an item in
-an address list is the string &"+caseful"&, the original case of the local
-part is restored for any comparisons that follow, and string comparisons are no
-longer case-independent. This does not affect the domain, which remains in
-lower case. However, although independent matches on the domain alone are still
-performed caselessly, regular expressions that match against an entire address
-become case-sensitive after &"+caseful"& has been seen.
-
-
-
-.section "Local part lists" "SECTlocparlis"
-.cindex "list" "local part list"
-.cindex "local part" "list"
-Case-sensitivity in local part lists is handled in the same way as for address
-lists, as just described. The &"+caseful"& item can be used if required. In a
-setting of the &%local_parts%& option in a router with &%caseful_local_part%&
-set false, the subject is lowercased and the matching is initially
-case-insensitive. In this case, &"+caseful"& will restore case-sensitive
-matching in the local part list, but not elsewhere in the router. If
-&%caseful_local_part%& is set true in a router, matching in the &%local_parts%&
-option is case-sensitive from the start.
-
-If a local part list is indirected to a file (see section &<<SECTfilnamlis>>&),
-comments are handled in the same way as address lists &-- they are recognized
-only if the # is preceded by white space or the start of the line.
-Otherwise, local part lists are matched in the same way as domain lists, except
-that the special items that refer to the local host (&`@`&, &`@[]`&,
-&`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`&) are not recognized.
-Refer to section &<<SECTdomainlist>>& for details of the other available item
-types.
-.ecindex IIDdohoadli
-
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "String expansions" "CHAPexpand"
-.scindex IIDstrexp "expansion" "of strings"
-Many strings in Exim's runtime configuration are expanded before use. Some of
-them are expanded every time they are used; others are expanded only once.
-
-When a string is being expanded it is copied verbatim from left to right except
-.cindex expansion "string concatenation"
-when a dollar or backslash character is encountered. A dollar specifies the
-start of a portion of the string that is interpreted and replaced as described
-below in section &<<SECTexpansionitems>>& onwards. Backslash is used as an
-escape character, as described in the following section.
-
-Whether a string is expanded depends upon the context.  Usually this is solely
-dependent upon the option for which a value is sought; in this documentation,
-options for which string expansion is performed are marked with &dagger; after
-the data type.  ACL rules always expand strings.  A couple of expansion
-conditions do not expand some of the brace-delimited branches, for security
-reasons,
-.cindex "tainted data" expansion
-.cindex expansion "tainted data"
-and expansion of data deriving from the sender (&"tainted data"&)
-is not permitted.
-
-
-
-.section "Literal text in expanded strings" "SECTlittext"
-.cindex "expansion" "including literal text"
-An uninterpreted dollar can be included in an expanded string by putting a
-backslash in front of it. A backslash can be used to prevent any special
-character being treated specially in an expansion, including backslash itself.
-If the string appears in quotes in the configuration file, two backslashes are
-required because the quotes themselves cause interpretation of backslashes when
-the string is read in (see section &<<SECTstrings>>&).
-
-.cindex "expansion" "non-expandable substrings"
-A portion of the string can specified as non-expandable by placing it between
-two occurrences of &`\N`&. This is particularly useful for protecting regular
-expressions, which often contain backslashes and dollar signs. For example:
-.code
-deny senders = \N^\d{8}[a-z]@some\.site\.example$\N
-.endd
-On encountering the first &`\N`&, the expander copies subsequent characters
-without interpretation until it reaches the next &`\N`& or the end of the
-string.
-
-
-
-.section "Character escape sequences in expanded strings" "SECID82"
-.cindex "expansion" "escape sequences"
-A backslash followed by one of the letters &"n"&, &"r"&, or &"t"& in an
-expanded string is recognized as an escape sequence for the character newline,
-carriage return, or tab, respectively. A backslash followed by up to three
-octal digits is recognized as an octal encoding for a single character, and a
-backslash followed by &"x"& and up to two hexadecimal digits is a hexadecimal
-encoding.
-
-These escape sequences are also recognized in quoted strings when they are read
-in. Their interpretation in expansions as well is useful for unquoted strings,
-and for other cases such as looked-up strings that are then expanded.
-
-
-.section "Testing string expansions" "SECID83"
-.cindex "expansion" "testing"
-.cindex "testing" "string expansion"
-.oindex "&%-be%&"
-Many expansions can be tested by calling Exim with the &%-be%& option. This
-takes the command arguments, or lines from the standard input if there are no
-arguments, runs them through the string expansion code, and writes the results
-to the standard output. Variables based on configuration values are set up, but
-since no message is being processed, variables such as &$local_part$& have no
-value. Nevertheless the &%-be%& option can be useful for checking out file and
-database lookups, and the use of expansion operators such as &%sg%&, &%substr%&
-and &%nhash%&.
-
-Exim gives up its root privilege when it is called with the &%-be%& option, and
-instead runs under the uid and gid it was called with, to prevent users from
-using &%-be%& for reading files to which they do not have access.
-
-.oindex "&%-bem%&"
-If you want to test expansions that include variables whose values are taken
-from a message, there are two other options that can be used. The &%-bem%&
-option is like &%-be%& except that it is followed by a filename. The file is
-read as a message before doing the test expansions. For example:
-.code
-exim -bem /tmp/test.message '$h_subject:'
-.endd
-The &%-Mset%& option is used in conjunction with &%-be%& and is followed by an
-Exim message identifier. For example:
-.code
-exim -be -Mset 1GrA8W-0004WS-LQ '$recipients'
-.endd
-This loads the message from Exim's spool before doing the test expansions, and
-is therefore restricted to admin users.
-
-
-.section "Forced expansion failure" "SECTforexpfai"
-.cindex "expansion" "forced failure"
-A number of expansions that are described in the following section have
-alternative &"true"& and &"false"& substrings, enclosed in brace characters
-(which are sometimes called &"curly brackets"&). Which of the two strings is
-used depends on some condition that is evaluated as part of the expansion. If,
-instead of a &"false"& substring, the word &"fail"& is used (not in braces),
-the entire string expansion fails in a way that can be detected by the code
-that requested the expansion. This is called &"forced expansion failure"&, and
-its consequences depend on the circumstances. In some cases it is no different
-from any other expansion failure, but in others a different action may be
-taken. Such variations are mentioned in the documentation of the option that is
-being expanded.
-
-
-
-
-.section "Expansion items" "SECTexpansionitems"
-The following items are recognized in expanded strings. White space may be used
-between sub-items that are keywords or substrings enclosed in braces inside an
-outer set of braces, to improve readability. &*Warning*&: Within braces,
-white space is significant.
-
-.vlist
-.vitem &*$*&<&'variable&~name'&>&~or&~&*${*&<&'variable&~name'&>&*}*&
-.cindex "expansion" "variables"
-Substitute the contents of the named variable, for example:
-.code
-$local_part
-${domain}
-.endd
-The second form can be used to separate the name from subsequent alphanumeric
-characters. This form (using braces) is available only for variables; it does
-&'not'& apply to message headers. The names of the variables are given in
-section &<<SECTexpvar>>& below. If the name of a non-existent variable is
-given, the expansion fails.
-
-.vitem &*${*&<&'op'&>&*:*&<&'string'&>&*}*&
-.cindex "expansion" "operators"
-The string is first itself expanded, and then the operation specified by
-<&'op'&> is applied to it. For example:
-.code
-${lc:$local_part}
-.endd
-The string starts with the first character after the colon, which may be
-leading white space. A list of operators is given in section &<<SECTexpop>>&
-below. The operator notation is used for simple expansion items that have just
-one argument, because it reduces the number of braces and therefore makes the
-string easier to understand.
-
-.vitem &*$bheader_*&<&'header&~name'&>&*:*&&~or&~&*$bh_*&<&'header&~name'&>&*:*&
-This item inserts &"basic"& header lines. It is described with the &%header%&
-expansion item below.
-
-
-.vitem "&*${acl{*&<&'name'&>&*}{*&<&'arg'&>&*}...}*&"
-.cindex "expansion" "calling an acl"
-.cindex "&%acl%&" "call from expansion"
-The name and zero to nine argument strings are first expanded separately.  The expanded
-arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
-Any unused are made empty.  The variable &$acl_narg$& is set to the number of
-arguments.  The named ACL (see chapter &<<CHAPACL>>&) is called
-and may use the variables; if another acl expansion is used the values
-are restored after it returns.  If the ACL sets
-a value using a "message =" modifier and returns accept or deny, the value becomes
-the result of the expansion.
-If no message is set and the ACL returns accept or deny
-the expansion result is an empty string.
-If the ACL returns defer the result is a forced-fail.  Otherwise the expansion fails.
-
-
-.vitem "&*${authresults{*&<&'authserv-id'&>&*}}*&"
-.cindex authentication "results header"
-.cindex headers "authentication-results:"
-.cindex authentication "expansion item"
-This item returns a string suitable for insertion as an
-&'Authentication-Results:'&
-header line.
-The given <&'authserv-id'&> is included in the result; typically this
-will be a domain name identifying the system performing the authentications.
-Methods that might be present in the result include:
-.code
-none
-iprev
-auth
-spf
-dkim
-.endd
-
-Example use (as an ACL modifier):
-.code
-      add_header = :at_start:${authresults {$primary_hostname}}
-.endd
-This is safe even if no authentication results are available.
-
-
-.vitem "&*${certextract{*&<&'field'&>&*}{*&<&'certificate'&>&*}&&&
-       {*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
-.cindex "expansion" "extracting certificate fields"
-.cindex "&%certextract%&" "certificate fields"
-.cindex "certificate" "extracting fields"
-The <&'certificate'&> must be a variable of type certificate.
-The field name is expanded and used to retrieve the relevant field from
-the certificate.  Supported fields are:
-.display
-&`version        `&
-&`serial_number  `&
-&`subject        `& RFC4514 DN
-&`issuer         `& RFC4514 DN
-&`notbefore      `& time
-&`notafter       `& time
-&`sig_algorithm  `&
-&`signature      `&
-&`subj_altname   `& tagged list
-&`ocsp_uri       `& list
-&`crl_uri        `& list
-.endd
-If the field is found,
-<&'string2'&> is expanded, and replaces the whole item;
-otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
-variable &$value$& contains the value that has been extracted. Afterwards, it
-is restored to any previous value it might have had.
-
-If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
-key is not found. If {<&'string2'&>} is also omitted, the value that was
-extracted is used.
-
-Some field names take optional modifiers, appended and separated by commas.
-
-The field selectors marked as "RFC4514" above
-output a Distinguished Name string which is
-not quite
-parseable by Exim as a comma-separated tagged list
-(the exceptions being elements containing commas).
-RDN elements of a single type may be selected by
-a modifier of the type label; if so the expansion
-result is a list (newline-separated by default).
-The separator may be changed by another modifier of
-a right angle-bracket followed immediately by the new separator.
-Recognised RDN type labels include "CN", "O", "OU" and "DC".
-
-The field selectors marked as "time" above
-take an optional modifier of "int"
-for which the result is the number of seconds since epoch.
-Otherwise the result is a human-readable string
-in the timezone selected by the main "timezone" option.
-
-The field selectors marked as "list" above return a list,
-newline-separated by default,
-(embedded separator characters in elements are doubled).
-The separator may be changed by a modifier of
-a right angle-bracket followed immediately by the new separator.
-
-The field selectors marked as "tagged" above
-prefix each list element with a type string and an equals sign.
-Elements of only one type may be selected by a modifier
-which is one of "dns", "uri" or "mail";
-if so the element tags are omitted.
-
-If not otherwise noted field values are presented in human-readable form.
-
-.vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&&
-       {*&<&'arg'&>&*}...}*&"
-.cindex &%dlfunc%&
-This expansion dynamically loads and then calls a locally-written C function.
-This functionality is available only if Exim is compiled with
-.code
-EXPAND_DLFUNC=yes
-.endd
-set in &_Local/Makefile_&. Once loaded, Exim remembers the dynamically loaded
-object so that it doesn't reload the same object file in the same Exim process
-(but of course Exim does start new processes frequently).
-
-There may be from zero to eight arguments to the function.
-
-When compiling
-a local function that is to be called in this way,
-first &_DLFUNC_IMPL_& should be defined,
-and second &_local_scan.h_& should be included.
-The Exim variables and functions that are defined by that API
-are also available for dynamically loaded functions. The function itself
-must have the following type:
-.code
-int dlfunction(uschar **yield, int argc, uschar *argv[])
-.endd
-Where &`uschar`& is a typedef for &`unsigned char`& in &_local_scan.h_&. The
-function should return one of the following values:
-
-&`OK`&: Success. The string that is placed in the variable &'yield'& is put
-into the expanded string that is being built.
-
-&`FAIL`&: A non-forced expansion failure occurs, with the error message taken
-from &'yield'&, if it is set.
-
-&`FAIL_FORCED`&: A forced expansion failure occurs, with the error message
-taken from &'yield'& if it is set.
-
-&`ERROR`&: Same as &`FAIL`&, except that a panic log entry is written.
-
-When compiling a function that is to be used in this way with gcc,
-you need to add &%-shared%& to the gcc command. Also, in the Exim build-time
-configuration, you must add &%-export-dynamic%& to EXTRALIBS.
-
-
-.vitem "&*${env{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&"
-.cindex "expansion" "extracting value from environment"
-.cindex "environment" "values from"
-The key is first expanded separately, and leading and trailing white space
-removed.
-This is then searched for as a name in the environment.
-If a variable is found then its value is placed in &$value$&
-and <&'string1'&> is expanded, otherwise <&'string2'&> is expanded.
-
-Instead of {<&'string2'&>} the word &"fail"& (not in curly brackets) can
-appear, for example:
-.code
-${env{USER}{$value} fail }
-.endd
-This forces an expansion failure (see section &<<SECTforexpfai>>&);
-{<&'string1'&>} must be present for &"fail"& to be recognized.
-
-If {<&'string2'&>} is omitted an empty string is substituted on
-search failure.
-If {<&'string1'&>} is omitted the search result is substituted on
-search success.
-
-The environment is adjusted by the &%keep_environment%& and
-&%add_environment%& main section options.
-
-
-.vitem "&*${extract{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
-       {*&<&'string3'&>&*}}*&"
-.cindex "expansion" "extracting substrings by key"
-.cindex "&%extract%&" "substrings by key"
-The key and <&'string1'&> are first expanded separately. Leading and trailing
-white space is removed from the key (but not from any of the strings). The key
-must not be empty and must not consist entirely of digits.
-The expanded <&'string1'&> must be of the form:
-.display
-<&'key1'&> = <&'value1'&>  <&'key2'&> = <&'value2'&> ...
-.endd
-.vindex "&$value$&"
-where the equals signs and spaces (but not both) are optional. If any of the
-values contain white space, they must be enclosed in double quotes, and any
-values that are enclosed in double quotes are subject to escape processing as
-described in section &<<SECTstrings>>&. The expanded <&'string1'&> is searched
-for the value that corresponds to the key. The search is case-insensitive. If
-the key is found, <&'string2'&> is expanded, and replaces the whole item;
-otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
-variable &$value$& contains the value that has been extracted. Afterwards, it
-is restored to any previous value it might have had.
-
-If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
-key is not found. If {<&'string2'&>} is also omitted, the value that was
-extracted is used. Thus, for example, these two expansions are identical, and
-yield &"2001"&:
-.code
-${extract{gid}{uid=1984 gid=2001}}
-${extract{gid}{uid=1984 gid=2001}{$value}}
-.endd
-Instead of {<&'string3'&>} the word &"fail"& (not in curly brackets) can
-appear, for example:
-.code
-${extract{Z}{A=... B=...}{$value} fail }
-.endd
-This forces an expansion failure (see section &<<SECTforexpfai>>&);
-{<&'string2'&>} must be present for &"fail"& to be recognized.
-
-.vitem "&*${extract json{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
-       {*&<&'string3'&>&*}}*&" &&&
-       "&*${extract jsons{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
-       {*&<&'string3'&>&*}}*&"
-.cindex "expansion" "extracting from JSON object"
-.cindex JSON expansions
-The key and <&'string1'&> are first expanded separately. Leading and trailing
-white space is removed from the key (but not from any of the strings). The key
-must not be empty and must not consist entirely of digits.
-The expanded <&'string1'&> must be of the form:
-.display
-{ <&'"key1"'&> : <&'value1'&> ,  <&'"key2"'&> , <&'value2'&> ... }
-.endd
-.vindex "&$value$&"
-The braces, commas and colons, and the quoting of the member name are required;
-the spaces are optional.
-Matching of the key against the member names is done case-sensitively.
-For the &"json"& variant,
-if a returned value is a JSON string, it retains its leading and
-trailing quotes.
-For the &"jsons"& variant, which is intended for use with JSON strings, the
-leading and trailing quotes are removed from the returned value.
-. XXX should be a UTF-8 compare
-
-The results of matching are handled as above.
-
-
-.vitem "&*${extract{*&<&'number'&>&*}{*&<&'separators'&>&*}&&&
-        {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
-.cindex "expansion" "extracting substrings by number"
-.cindex "&%extract%&" "substrings by number"
-The <&'number'&> argument must consist entirely of decimal digits,
-apart from leading and trailing white space, which is ignored.
-This is what distinguishes this form of &%extract%& from the previous kind. It
-behaves in the same way, except that, instead of extracting a named field, it
-extracts from <&'string1'&> the field whose number is given as the first
-argument. You can use &$value$& in <&'string2'&> or &`fail`& instead of
-<&'string3'&> as before.
-
-The fields in the string are separated by any one of the characters in the
-separator string. These may include space or tab characters.
-The first field is numbered one. If the number is negative, the fields are
-counted from the end of the string, with the rightmost one numbered -1. If the
-number given is zero, the entire string is returned. If the modulus of the
-number is greater than the number of fields in the string, the result is the
-expansion of <&'string3'&>, or the empty string if <&'string3'&> is not
-provided. For example:
-.code
-${extract{2}{:}{x:42:99:& Mailer::/bin/bash}}
-.endd
-yields &"42"&, and
-.code
-${extract{-4}{:}{x:42:99:& Mailer::/bin/bash}}
-.endd
-yields &"99"&. Two successive separators mean that the field between them is
-empty (for example, the fifth field above).
-
-
-.vitem "&*${extract json {*&<&'number'&>&*}}&&&
-        {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&" &&&
-       "&*${extract jsons{*&<&'number'&>&*}}&&&
-        {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
-.cindex "expansion" "extracting from JSON array"
-.cindex JSON expansions
-The <&'number'&> argument must consist entirely of decimal digits,
-apart from leading and trailing white space, which is ignored.
-
-Field selection and result handling is as above;
-there is no choice of field separator.
-For the &"json"& variant,
-if a returned value is a JSON string, it retains its leading and
-trailing quotes.
-For the &"jsons"& variant, which is intended for use with JSON strings, the
-leading and trailing quotes are removed from the returned value.
-
-
-.vitem &*${filter{*&<&'string'&>&*}{*&<&'condition'&>&*}}*&
-.cindex "list" "selecting by condition"
-.cindex "expansion" "selecting from list by condition"
-.vindex "&$item$&"
-After expansion, <&'string'&> is interpreted as a list, colon-separated by
-default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
-For each item
-in this list, its value is place in &$item$&, and then the condition is
-evaluated. If the condition is true, &$item$& is added to the output as an
-item in a new list; if the condition is false, the item is discarded. The
-separator used for the output list is the same as the one used for the
-input, but a separator setting is not included in the output. For example:
-.code
-${filter{a:b:c}{!eq{$item}{b}}}
-.endd
-yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored
-to what it was before. See also the &%map%& and &%reduce%& expansion items.
-
-
-.vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
-.cindex "hash function" "textual"
-.cindex "expansion" "textual hash"
-This is a textual hashing function, and was the first to be implemented in
-early versions of Exim. In current releases, there are other hashing functions
-(numeric, MD5, and SHA-1), which are described below.
-
-The first two strings, after expansion, must be numbers. Call them <&'m'&> and
-<&'n'&>. If you are using fixed values for these numbers, that is, if
-<&'string1'&> and <&'string2'&> do not change when they are expanded, you can
-use the simpler operator notation that avoids some of the braces:
-.code
-${hash_<n>_<m>:<string>}
-.endd
-The second number is optional (in both notations). If <&'n'&> is greater than
-or equal to the length of the string, the expansion item returns the string.
-Otherwise it computes a new string of length <&'n'&> by applying a hashing
-function to the string. The new string consists of characters taken from the
-first <&'m'&> characters of the string
-.code
-abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQWRSTUVWXYZ0123456789
-.endd
-If <&'m'&> is not present the value 26 is used, so that only lower case
-letters appear. For example:
-.display
-&`$hash{3}{monty}}           `&   yields  &`jmg`&
-&`$hash{5}{monty}}           `&   yields  &`monty`&
-&`$hash{4}{62}{monty python}}`&   yields  &`fbWx`&
-.endd
-
-.vitem "&*$header_*&<&'header&~name'&>&*:*&&~or&~&&&
-        &*$h_*&<&'header&~name'&>&*:*&" &&&
-       "&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&&
-        &*$bh_*&<&'header&~name'&>&*:*&" &&&
-       "&*$lheader_*&<&'header&~name'&>&*:*&&~or&~&&&
-        &*$lh_*&<&'header&~name'&>&*:*&" &&&
-       "&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&&
-        &*$rh_*&<&'header&~name'&>&*:*&"
-.cindex "expansion" "header insertion"
-.vindex "&$header_$&"
-.vindex "&$bheader_$&"
-.vindex "&$lheader_$&"
-.vindex "&$rheader_$&"
-.cindex "header lines" "in expansion strings"
-.cindex "header lines" "character sets"
-.cindex "header lines" "decoding"
-Substitute the contents of the named message header line, for example
-.code
-$header_reply-to:
-.endd
-The newline that terminates a header line is not included in the expansion, but
-internal newlines (caused by splitting the header line over several physical
-lines) may be present.
-
-The difference between the four pairs of expansions is in the way
-the data in the header line is interpreted.
-
-.ilist
-.cindex "white space" "in header lines"
-&%rheader%& gives the original &"raw"& content of the header line, with no
-processing at all, and without the removal of leading and trailing white space.
-
-.next
-.cindex "list" "of header lines"
-&%lheader%& gives a colon-separated list, one element per header when there
-are multiple headers with a given name.
-Any embedded colon characters within an element are doubled, so normal Exim
-list-processing facilities can be used.
-The terminating newline of each element is removed; in other respects
-the content is &"raw"&.
-
-.next
-.cindex "base64 encoding" "in header lines"
-&%bheader%& removes leading and trailing white space, and then decodes base64
-or quoted-printable MIME &"words"& within the header text, but does no
-character set translation. If decoding of what looks superficially like a MIME
-&"word"& fails, the raw string is returned. If decoding
-.cindex "binary zero" "in header line"
-produces a binary zero character, it is replaced by a question mark &-- this is
-what Exim does for binary zeros that are actually received in header lines.
-
-.next
-&%header%& tries to translate the string as decoded by &%bheader%& to a
-standard character set. This is an attempt to produce the same string as would
-be displayed on a user's MUA. If translation fails, the &%bheader%& string is
-returned. Translation is attempted only on operating systems that support the
-&[iconv()]& function. This is indicated by the compile-time macro HAVE_ICONV in
-a system Makefile or in &_Local/Makefile_&.
-.endlist ilist
-
-In a filter file, the target character set for &%header%& can be specified by a
-command of the following form:
-.code
-headers charset "UTF-8"
-.endd
-This command affects all references to &$h_$& (or &$header_$&) expansions in
-subsequently obeyed filter commands. In the absence of this command, the target
-character set in a filter is taken from the setting of the &%headers_charset%&
-option in the runtime configuration. The value of this option defaults to the
-value of HEADERS_CHARSET in &_Local/Makefile_&. The ultimate default is
-ISO-8859-1.
-
-Header names follow the syntax of RFC 2822, which states that they may contain
-any printing characters except space and colon. Consequently, curly brackets
-&'do not'& terminate header names, and should not be used to enclose them as
-if they were variables. Attempting to do so causes a syntax error.
-
-Only header lines that are common to all copies of a message are visible to
-this mechanism. These are the original header lines that are received with the
-message, and any that are added by an ACL statement or by a system
-filter. Header lines that are added to a particular copy of a message by a
-router or transport are not accessible.
-
-For incoming SMTP messages, no header lines are visible in
-ACLs that are obeyed before the data phase completes,
-because the header structure is not set up until the message is received.
-They are visible in DKIM, PRDR and DATA ACLs.
-Header lines that are added in a RCPT ACL (for example)
-are saved until the message's incoming header lines are available, at which
-point they are added.
-When any of the above ACLs ar
-running, however, header lines added by earlier ACLs are visible.
-
-Upper case and lower case letters are synonymous in header names. If the
-following character is white space, the terminating colon may be omitted, but
-this is not recommended, because you may then forget it when it is needed. When
-white space terminates the header name, this white space is included in the
-expanded string.  If the message does not contain the given header, the
-expansion item is replaced by an empty string. (See the &%def%& condition in
-section &<<SECTexpcond>>& for a means of testing for the existence of a
-header.)
-
-If there is more than one header with the same name, they are all concatenated
-to form the substitution string, up to a maximum length of 64K. Unless
-&%rheader%& is being used, leading and trailing white space is removed from
-each header before concatenation, and a completely empty header is ignored. A
-newline character is then inserted between non-empty headers, but there is no
-newline at the very end. For the &%header%& and &%bheader%& expansion, for
-those headers that contain lists of addresses, a comma is also inserted at the
-junctions between headers. This does not happen for the &%rheader%& expansion.
-
-.new
-.cindex "tainted data"
-When the headers are from an incoming message,
-the result of expanding any of these variables is tainted.
-.wen
-
-
-.vitem &*${hmac{*&<&'hashname'&>&*}{*&<&'secret'&>&*}{*&<&'string'&>&*}}*&
-.cindex "expansion" "hmac hashing"
-.cindex &%hmac%&
-This function uses cryptographic hashing (either MD5 or SHA-1) to convert a
-shared secret and some text into a message authentication code, as specified in
-RFC 2104. This differs from &`${md5:secret_text...}`& or
-&`${sha1:secret_text...}`& in that the hmac step adds a signature to the
-cryptographic hash, allowing for authentication that is not possible with MD5
-or SHA-1 alone. The hash name must expand to either &`md5`& or &`sha1`& at
-present. For example:
-.code
-${hmac{md5}{somesecret}{$primary_hostname $tod_log}}
-.endd
-For the hostname &'mail.example.com'& and time 2002-10-17 11:30:59, this
-produces:
-.code
-dd97e3ba5d1a61b5006108f8c8252953
-.endd
-As an example of how this might be used, you might put in the main part of
-an Exim configuration:
-.code
-SPAMSCAN_SECRET=cohgheeLei2thahw
-.endd
-In a router or a transport you could then have:
-.code
-headers_add = \
-  X-Spam-Scanned: ${primary_hostname} ${message_exim_id} \
-  ${hmac{md5}{SPAMSCAN_SECRET}\
-  {${primary_hostname},${message_exim_id},$h_message-id:}}
-.endd
-Then given a message, you can check where it was scanned by looking at the
-&'X-Spam-Scanned:'& header line. If you know the secret, you can check that
-this header line is authentic by recomputing the authentication code from the
-host name, message ID and the &'Message-id:'& header line. This can be done
-using Exim's &%-be%& option, or by other means, for example, by using the
-&'hmac_md5_hex()'& function in Perl.
-
-
-.vitem &*${if&~*&<&'condition'&>&*&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
-.cindex "expansion" "conditional"
-.cindex "&%if%&, expansion item"
-If <&'condition'&> is true, <&'string1'&> is expanded and replaces the whole
-item; otherwise <&'string2'&> is used. The available conditions are described
-in section &<<SECTexpcond>>& below. For example:
-.code
-${if eq {$local_part}{postmaster} {yes}{no} }
-.endd
-The second string need not be present; if it is not and the condition is not
-true, the item is replaced with nothing. Alternatively, the word &"fail"& may
-be present instead of the second string (without any curly brackets). In this
-case, the expansion is forced to fail if the condition is not true (see section
-&<<SECTforexpfai>>&).
-
-If both strings are omitted, the result is the string &`true`& if the condition
-is true, and the empty string if the condition is false. This makes it less
-cumbersome to write custom ACL and router conditions. For example, instead of
-.code
-condition = ${if >{$acl_m4}{3}{true}{false}}
-.endd
-you can use
-.code
-condition = ${if >{$acl_m4}{3}}
-.endd
-
-
-
-.vitem &*${imapfolder{*&<&'foldername'&>&*}}*&
-.cindex expansion "imap folder"
-.cindex "&%imapfolder%& expansion item"
-This item converts a (possibly multilevel, or with non-ASCII characters)
-folder specification to a Maildir name for filesystem use.
-For information on internationalisation support see &<<SECTi18nMDA>>&.
-
-
-
-.vitem &*${length{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
-.cindex "expansion" "string truncation"
-.cindex "&%length%& expansion item"
-The &%length%& item is used to extract the initial portion of a string. Both
-strings are expanded, and the first one must yield a number, <&'n'&>, say. If
-you are using a fixed value for the number, that is, if <&'string1'&> does not
-change when expanded, you can use the simpler operator notation that avoids
-some of the braces:
-.code
-${length_<n>:<string>}
-.endd
-The result of this item is either the first <&'n'&> bytes or the whole
-of <&'string2'&>, whichever is the shorter. Do not confuse &%length%& with
-&%strlen%&, which gives the length of a string.
-All measurement is done in bytes and is not UTF-8 aware.
-
-
-.vitem "&*${listextract{*&<&'number'&>&*}&&&
-        {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
-.cindex "expansion" "extracting list elements by number"
-.cindex "&%listextract%&" "extract list elements by number"
-.cindex "list" "extracting elements by number"
-The <&'number'&> argument must consist entirely of decimal digits,
-apart from an optional leading minus,
-and leading and trailing white space (which is ignored).
-
-After expansion, <&'string1'&> is interpreted as a list, colon-separated by
-default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
-
-The first field of the list is numbered one.
-If the number is negative, the fields are
-counted from the end of the list, with the rightmost one numbered -1.
-The numbered element of the list is extracted and placed in &$value$&,
-then <&'string2'&> is expanded as the result.
-
-If the modulus of the
-number is zero or greater than the number of fields in the string,
-the result is the expansion of <&'string3'&>.
-
-For example:
-.code
-${listextract{2}{x:42:99}}
-.endd
-yields &"42"&, and
-.code
-${listextract{-3}{<, x,42,99,& Mailer,,/bin/bash}{result: $value}}
-.endd
-yields &"result: 42"&.
-
-If {<&'string3'&>} is omitted, an empty string is used for string3.
-If {<&'string2'&>} is also omitted, the value that was
-extracted is used.
-You can use &`fail`& instead of {<&'string3'&>} as in a string extract.
-
-
-.vitem "&*${lookup{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
-        {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
-This is the first of one of two different types of lookup item, which are both
-described in the next item.
-
-.vitem "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&&
-        {*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
-.cindex "expansion" "lookup in"
-.cindex "file" "lookups"
-.cindex "lookup" "in expanded string"
-The two forms of lookup item specify data lookups in files and databases, as
-discussed in chapter &<<CHAPfdlookup>>&. The first form is used for single-key
-lookups, and the second is used for query-style lookups. The <&'key'&>,
-<&'file'&>, and <&'query'&> strings are expanded before use.
-
-If there is any white space in a lookup item which is part of a filter command,
-a retry or rewrite rule, a routing rule for the &(manualroute)& router, or any
-other place where white space is significant, the lookup item must be enclosed
-in double quotes. The use of data lookups in users' filter files may be locked
-out by the system administrator.
-
-.vindex "&$value$&"
-If the lookup succeeds, <&'string1'&> is expanded and replaces the entire item.
-During its expansion, the variable &$value$& contains the data returned by the
-lookup. Afterwards it reverts to the value it had previously (at the outer
-level it is empty). If the lookup fails, <&'string2'&> is expanded and replaces
-the entire item. If {<&'string2'&>} is omitted, the replacement is the empty
-string on failure. If <&'string2'&> is provided, it can itself be a nested
-lookup, thus providing a mechanism for looking up a default value when the
-original lookup fails.
-
-If a nested lookup is used as part of <&'string1'&>, &$value$& contains the
-data for the outer lookup while the parameters of the second lookup are
-expanded, and also while <&'string2'&> of the second lookup is expanded, should
-the second lookup fail. Instead of {<&'string2'&>} the word &"fail"& can
-appear, and in this case, if the lookup fails, the entire expansion is forced
-to fail (see section &<<SECTforexpfai>>&). If both {<&'string1'&>} and
-{<&'string2'&>} are omitted, the result is the looked up value in the case of a
-successful lookup, and nothing in the case of failure.
-
-For single-key lookups, the string &"partial"& is permitted to precede the
-search type in order to do partial matching, and * or *@ may follow a search
-type to request default lookups if the key does not match (see sections
-&<<SECTdefaultvaluelookups>>& and &<<SECTpartiallookup>>& for details).
-
-.cindex "numerical variables (&$1$& &$2$& etc)" "in lookup expansion"
-If a partial search is used, the variables &$1$& and &$2$& contain the wild
-and non-wild parts of the key during the expansion of the replacement text.
-They return to their previous values at the end of the lookup item.
-
-This example looks up the postmaster alias in the conventional alias file:
-.code
-${lookup {postmaster} lsearch {/etc/aliases} {$value}}
-.endd
-This example uses NIS+ to look up the full name of the user corresponding to
-the local part of an address, forcing the expansion to fail if it is not found:
-.code
-${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \
-  {$value}fail}
-.endd
-
-
-.vitem &*${map{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
-.cindex "expansion" "list creation"
-.vindex "&$item$&"
-After expansion, <&'string1'&> is interpreted as a list, colon-separated by
-default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
-For each item
-in this list, its value is place in &$item$&, and then <&'string2'&> is
-expanded and added to the output as an item in a new list. The separator used
-for the output list is the same as the one used for the input, but a separator
-setting is not included in the output. For example:
-.code
-${map{a:b:c}{[$item]}} ${map{<- x-y-z}{($item)}}
-.endd
-expands to &`[a]:[b]:[c] (x)-(y)-(z)`&. At the end of the expansion, the
-value of &$item$& is restored to what it was before. See also the &%filter%&
-and &%reduce%& expansion items.
-
-.vitem &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
-.cindex "expansion" "numeric hash"
-.cindex "hash function" "numeric"
-The three strings are expanded; the first two must yield numbers. Call them
-<&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
-if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
-can use the simpler operator notation that avoids some of the braces:
-.code
-${nhash_<n>_<m>:<string>}
-.endd
-The second number is optional (in both notations). If there is only one number,
-the result is a number in the range 0&--<&'n'&>-1. Otherwise, the string is
-processed by a div/mod hash function that returns two numbers, separated by a
-slash, in the ranges 0 to <&'n'&>-1 and 0 to <&'m'&>-1, respectively. For
-example,
-.code
-${nhash{8}{64}{supercalifragilisticexpialidocious}}
-.endd
-returns the string &"6/33"&.
-
-
-
-.vitem &*${perl{*&<&'subroutine'&>&*}{*&<&'arg'&>&*}{*&<&'arg'&>&*}...}*&
-.cindex "Perl" "use in expanded string"
-.cindex "expansion" "calling Perl from"
-This item is available only if Exim has been built to include an embedded Perl
-interpreter. The subroutine name and the arguments are first separately
-expanded, and then the Perl subroutine is called with those arguments. No
-additional arguments need be given; the maximum number permitted, including the
-name of the subroutine, is nine.
-
-The return value of the subroutine is inserted into the expanded string, unless
-the return value is &%undef%&. In that case, the expansion fails in the same
-way as an explicit &"fail"& on a lookup item. The return value is a scalar.
-Whatever you return is evaluated in a scalar context. For example, if you
-return the name of a Perl vector, the return value is the size of the vector,
-not its contents.
-
-If the subroutine exits by calling Perl's &%die%& function, the expansion fails
-with the error message that was passed to &%die%&. More details of the embedded
-Perl facility are given in chapter &<<CHAPperl>>&.
-
-The &(redirect)& router has an option called &%forbid_filter_perl%& which locks
-out the use of this expansion item in filter files.
-
-
-.vitem &*${prvs{*&<&'address'&>&*}{*&<&'secret'&>&*}{*&<&'keynumber'&>&*}}*&
-.cindex "&%prvs%& expansion item"
-The first argument is a complete email address and the second is secret
-keystring. The third argument, specifying a key number, is optional. If absent,
-it defaults to 0. The result of the expansion is a prvs-signed email address,
-to be typically used with the &%return_path%& option on an &(smtp)& transport
-as part of a bounce address tag validation (BATV) scheme. For more discussion
-and an example, see section &<<SECTverifyPRVS>>&.
-
-.vitem "&*${prvscheck{*&<&'address'&>&*}{*&<&'secret'&>&*}&&&
-        {*&<&'string'&>&*}}*&"
-.cindex "&%prvscheck%& expansion item"
-This expansion item is the complement of the &%prvs%& item. It is used for
-checking prvs-signed addresses. If the expansion of the first argument does not
-yield a syntactically valid prvs-signed address, the whole item expands to the
-empty string. When the first argument does expand to a syntactically valid
-prvs-signed address, the second argument is expanded, with the prvs-decoded
-version of the address and the key number extracted from the address in the
-variables &$prvscheck_address$& and &$prvscheck_keynum$&, respectively.
-
-These two variables can be used in the expansion of the second argument to
-retrieve the secret. The validity of the prvs-signed address is then checked
-against the secret. The result is stored in the variable &$prvscheck_result$&,
-which is empty for failure or &"1"& for success.
-
-The third argument is optional; if it is missing, it defaults to an empty
-string. This argument is now expanded. If the result is an empty string, the
-result of the expansion is the decoded version of the address. This is the case
-whether or not the signature was valid. Otherwise, the result of the expansion
-is the expansion of the third argument.
-
-All three variables can be used in the expansion of the third argument.
-However, once the expansion is complete, only &$prvscheck_result$& remains set.
-For more discussion and an example, see section &<<SECTverifyPRVS>>&.
-
-.vitem &*${readfile{*&<&'file&~name'&>&*}{*&<&'eol&~string'&>&*}}*&
-.cindex "expansion" "inserting an entire file"
-.cindex "file" "inserting into expansion"
-.cindex "&%readfile%& expansion item"
-The filename and end-of-line string are first expanded separately. The file is
-then read, and its contents replace the entire item. All newline characters in
-the file are replaced by the end-of-line string if it is present. Otherwise,
-newlines are left in the string.
-String expansion is not applied to the contents of the file. If you want this,
-you must wrap the item in an &%expand%& operator. If the file cannot be read,
-the string expansion fails.
-
-The &(redirect)& router has an option called &%forbid_filter_readfile%& which
-locks out the use of this expansion item in filter files.
-
-
-
-.vitem "&*${readsocket{*&<&'name'&>&*}{*&<&'request'&>&*}&&&
-        {*&<&'options'&>&*}{*&<&'eol&~string'&>&*}{*&<&'fail&~string'&>&*}}*&"
-.cindex "expansion" "inserting from a socket"
-.cindex "socket, use of in expansion"
-.cindex "&%readsocket%& expansion item"
-This item inserts data from a Unix domain or TCP socket into the expanded
-string. The minimal way of using it uses just two arguments, as in these
-examples:
-.code
-${readsocket{/socket/name}{request string}}
-${readsocket{inet:some.host:1234}{request string}}
-.endd
-For a Unix domain socket, the first substring must be the path to the socket.
-For an Internet socket, the first substring must contain &`inet:`& followed by
-a host name or IP address, followed by a colon and a port, which can be a
-number or the name of a TCP port in &_/etc/services_&. An IP address may
-optionally be enclosed in square brackets. This is best for IPv6 addresses. For
-example:
-.code
-${readsocket{inet:[::1]:1234}{request string}}
-.endd
-Only a single host name may be given, but if looking it up yields more than
-one IP address, they are each tried in turn until a connection is made. For
-both kinds of socket, Exim makes a connection, writes the request string
-unless it is an empty string; and no terminating NUL is ever sent)
-and reads from the socket until an end-of-file
-is read. A timeout of 5 seconds is applied. Additional, optional arguments
-extend what can be done. Firstly, you can vary the timeout. For example:
-.code
-${readsocket{/socket/name}{request string}{3s}}
-.endd
-
-The third argument is a list of options, of which the first element is the timeout
-and must be present if any options are given.
-Further elements are options of form &'name=value'&.
-Example:
-.code
-${readsocket{/socket/name}{request string}{3s:shutdown=no}}
-.endd
-
-.new
-The following option names are recognised:
-.ilist
-&*buf*&
-Only relevant for plaintext (non-TLS) connections.
-This defines buferring used when readong from the socket.
-Values are &"line"& (the default), &"full"& and &"no"& (meaning none).
-.next
-
-&*cache*&
-Defines if the result data can be cached for use by a later identical
-request in the same process.
-Values are &"yes"& or &"no"& (the default).
-If not, all cached results for this connection specification
-will be invalidated.
-
-.next
-&*keepopen*&
-If set to &"yes"& the socket will be left open for a later call
-to the same service, and also no shutdown (see below) will be done.
-The default is &"no"&.
-
-.next
-&*shutdown*&
-Defines whether or not a write-shutdown is done on the connection after
-sending the request. Values are &"yes"& (the default) or &"no"&
-(preferred, eg. by some webservers).
-
-.next
-&*tls*&
-Controls the use of TLS on the connection.
-Values are &"yes"& or &"no"& (the default).
-If it is enabled, a shutdown as descripbed above is never done.
-.endlist
-.wen
-
-
-A fourth argument allows you to change any newlines that are in the data
-that is read, in the same way as for &%readfile%& (see above). This example
-turns them into spaces:
-.code
-${readsocket{inet:127.0.0.1:3294}{request string}{3s}{ }}
-.endd
-As with all expansions, the substrings are expanded before the processing
-happens. Errors in these sub-expansions cause the expansion to fail. In
-addition, the following errors can occur:
-
-.ilist
-Failure to create a socket file descriptor;
-.next
-Failure to connect the socket;
-.next
-Failure to write the request string;
-.next
-Timeout on reading from the socket.
-.endlist
-
-By default, any of these errors causes the expansion to fail. However, if
-you supply a fifth substring, it is expanded and used when any of the above
-errors occurs. For example:
-.code
-${readsocket{/socket/name}{request string}{3s}{\n}\
-  {socket failure}}
-.endd
-You can test for the existence of a Unix domain socket by wrapping this
-expansion in &`${if exists`&, but there is a race condition between that test
-and the actual opening of the socket, so it is safer to use the fifth argument
-if you want to be absolutely sure of avoiding an expansion error for a
-non-existent Unix domain socket, or a failure to connect to an Internet socket.
-
-The &(redirect)& router has an option called &%forbid_filter_readsocket%& which
-locks out the use of this expansion item in filter files.
-
-
-.vitem &*${reduce{*&<&'string1'&>}{<&'string2'&>&*}{*&<&'string3'&>&*}}*&
-.cindex "expansion" "reducing a list to a scalar"
-.cindex "list" "reducing to a scalar"
-.vindex "&$value$&"
-.vindex "&$item$&"
-This operation reduces a list to a single, scalar string. After expansion,
-<&'string1'&> is interpreted as a list, colon-separated by default, but the
-separator can be changed in the usual way (&<<SECTlistsepchange>>&).
-Then <&'string2'&> is expanded and
-assigned to the &$value$& variable. After this, each item in the <&'string1'&>
-list is assigned to &$item$&, in turn, and <&'string3'&> is expanded for each of
-them. The result of that expansion is assigned to &$value$& before the next
-iteration. When the end of the list is reached, the final value of &$value$& is
-added to the expansion output. The &%reduce%& expansion item can be used in a
-number of ways. For example, to add up a list of numbers:
-.code
-${reduce {<, 1,2,3}{0}{${eval:$value+$item}}}
-.endd
-The result of that expansion would be &`6`&. The maximum of a list of numbers
-can be found:
-.code
-${reduce {3:0:9:4:6}{0}{${if >{$item}{$value}{$item}{$value}}}}
-.endd
-At the end of a &*reduce*& expansion, the values of &$item$& and &$value$& are
-restored to what they were before. See also the &%filter%& and &%map%&
-expansion items.
-
-.vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*&
-This item inserts &"raw"& header lines. It is described with the &%header%&
-expansion item in section &<<SECTexpansionitems>>& above.
-
-.vitem "&*${run{*&<&'command'&>&*&~*&<&'args'&>&*}{*&<&'string1'&>&*}&&&
-        {*&<&'string2'&>&*}}*&"
-.cindex "expansion" "running a command"
-.cindex "&%run%& expansion item"
-The command and its arguments are first expanded as one string. The string is
-split apart into individual arguments by spaces, and then the command is run
-in a separate process, but under the same uid and gid.  As in other command
-executions from Exim, a shell is not used by default. If the command requires
-a shell, you must explicitly code it.
-
-Since the arguments are split by spaces, when there is a variable expansion
-which has an empty result, it will cause the situation that the argument will
-simply be omitted when the program is actually executed by Exim. If the
-script/program requires a specific number of arguments and the expanded
-variable could possibly result in this empty expansion, the variable must be
-quoted. This is more difficult if the expanded variable itself could result
-in a string containing quotes, because it would interfere with the quotes
-around the command arguments. A possible guard against this is to wrap the
-variable in the &%sg%& operator to change any quote marks to some other
-character.
-
-The standard input for the command exists, but is empty. The standard output
-and standard error are set to the same file descriptor.
-.cindex "return code" "from &%run%& expansion"
-.vindex "&$value$&"
-If the command succeeds (gives a zero return code) <&'string1'&> is expanded
-and replaces the entire item; during this expansion, the standard output/error
-from the command is in the variable &$value$&. If the command fails,
-<&'string2'&>, if present, is expanded and used. Once again, during the
-expansion, the standard output/error from the command is in the variable
-&$value$&.
-
-If <&'string2'&> is absent, the result is empty. Alternatively, <&'string2'&>
-can be the word &"fail"& (not in braces) to force expansion failure if the
-command does not succeed. If both strings are omitted, the result is contents
-of the standard output/error on success, and nothing on failure.
-
-.vindex "&$run_in_acl$&"
-The standard output/error of the command is put in the variable &$value$&.
-In this ACL example, the output of a command is logged for the admin to
-troubleshoot:
-.code
-warn  condition    = ${run{/usr/bin/id}{yes}{no}}
-      log_message  = Output of id: $value
-.endd
-If the command requires shell idioms, such as the > redirect operator, the
-shell must be invoked directly, such as with:
-.code
-${run{/bin/bash -c "/usr/bin/id >/tmp/id"}{yes}{yes}}
-.endd
-
-.vindex "&$runrc$&"
-The return code from the command is put in the variable &$runrc$&, and this
-remains set afterwards, so in a filter file you can do things like this:
-.code
-if "${run{x y z}{}}$runrc" is 1 then ...
-  elif $runrc is 2 then ...
-  ...
-endif
-.endd
-If execution of the command fails (for example, the command does not exist),
-the return code is 127 &-- the same code that shells use for non-existent
-commands.
-
-&*Warning*&: In a router or transport, you cannot assume the order in which
-option values are expanded, except for those preconditions whose order of
-testing is documented. Therefore, you cannot reliably expect to set &$runrc$&
-by the expansion of one option, and use it in another.
-
-The &(redirect)& router has an option called &%forbid_filter_run%& which locks
-out the use of this expansion item in filter files.
-
-
-.vitem &*${sg{*&<&'subject'&>&*}{*&<&'regex'&>&*}{*&<&'replacement'&>&*}}*&
-.cindex "expansion" "string substitution"
-.cindex "&%sg%& expansion item"
-This item works like Perl's substitution operator (s) with the global (/g)
-option; hence its name. However, unlike the Perl equivalent, Exim does not
-modify the subject string; instead it returns the modified string for insertion
-into the overall expansion. The item takes three arguments: the subject string,
-a regular expression, and a substitution string. For example:
-.code
-${sg{abcdefabcdef}{abc}{xyz}}
-.endd
-yields &"xyzdefxyzdef"&. Because all three arguments are expanded before use,
-if any $, } or \ characters are required in the regular expression or in the
-substitution string, they have to be escaped. For example:
-.code
-${sg{abcdef}{^(...)(...)\$}{\$2\$1}}
-.endd
-yields &"defabc"&, and
-.code
-${sg{1=A 4=D 3=C}{\N(\d+)=\N}{K\$1=}}
-.endd
-yields &"K1=A K4=D K3=C"&. Note the use of &`\N`& to protect the contents of
-the regular expression from string expansion.
-
-The regular expression is compiled in 8-bit mode, working against bytes
-rather than any Unicode-aware character handling.
-
-
-.vitem &*${sort{*&<&'string'&>&*}{*&<&'comparator'&>&*}{*&<&'extractor'&>&*}}*&
-.cindex sorting "a list"
-.cindex list sorting
-.cindex expansion "list sorting"
-After expansion, <&'string'&> is interpreted as a list, colon-separated by
-default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
-The <&'comparator'&> argument is interpreted as the operator
-of a two-argument expansion condition.
-The numeric operators plus ge, gt, le, lt (and ~i variants) are supported.
-The comparison should return true when applied to two values
-if the first value should sort before the second value.
-The <&'extractor'&> expansion is applied repeatedly to elements of the list,
-the element being placed in &$item$&,
-to give values for comparison.
-
-The item result is a sorted list,
-with the original list separator,
-of the list elements (in full) of the original.
-
-Examples:
-.code
-${sort{3:2:1:4}{<}{$item}}
-.endd
-sorts a list of numbers, and
-.code
-${sort {${lookup dnsdb{>:,,mx=example.com}}} {<} {${listextract{1}{<,$item}}}}
-.endd
-will sort an MX lookup into priority order.
-
-
-.vitem &*${substr{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
-.cindex "&%substr%& expansion item"
-.cindex "substring extraction"
-.cindex "expansion" "substring extraction"
-The three strings are expanded; the first two must yield numbers. Call them
-<&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
-if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
-can use the simpler operator notation that avoids some of the braces:
-.code
-${substr_<n>_<m>:<string>}
-.endd
-The second number is optional (in both notations).
-If it is absent in the simpler format, the preceding underscore must also be
-omitted.
-
-The &%substr%& item can be used to extract more general substrings than
-&%length%&. The first number, <&'n'&>, is a starting offset, and <&'m'&> is the
-length required. For example
-.code
-${substr{3}{2}{$local_part}}
-.endd
-If the starting offset is greater than the string length the result is the
-null string; if the length plus starting offset is greater than the string
-length, the result is the right-hand part of the string, starting from the
-given offset. The first byte (character) in the string has offset zero.
-
-The &%substr%& expansion item can take negative offset values to count
-from the right-hand end of its operand. The last byte (character) is offset -1,
-the second-last is offset -2, and so on. Thus, for example,
-.code
-${substr{-5}{2}{1234567}}
-.endd
-yields &"34"&. If the absolute value of a negative offset is greater than the
-length of the string, the substring starts at the beginning of the string, and
-the length is reduced by the amount of overshoot. Thus, for example,
-.code
-${substr{-5}{2}{12}}
-.endd
-yields an empty string, but
-.code
-${substr{-3}{2}{12}}
-.endd
-yields &"1"&.
-
-When the second number is omitted from &%substr%&, the remainder of the string
-is taken if the offset is positive. If it is negative, all bytes (characters) in the
-string preceding the offset point are taken. For example, an offset of -1 and
-no length, as in these semantically identical examples:
-.code
-${substr_-1:abcde}
-${substr{-1}{abcde}}
-.endd
-yields all but the last character of the string, that is, &"abcd"&.
-
-All measurement is done in bytes and is not UTF-8 aware.
-
-
-
-.vitem "&*${tr{*&<&'subject'&>&*}{*&<&'characters'&>&*}&&&
-        {*&<&'replacements'&>&*}}*&"
-.cindex "expansion" "character translation"
-.cindex "&%tr%& expansion item"
-This item does single-character (in bytes) translation on its subject string. The second
-argument is a list of characters to be translated in the subject string. Each
-matching character is replaced by the corresponding character from the
-replacement list. For example
-.code
-${tr{abcdea}{ac}{13}}
-.endd
-yields &`1b3de1`&. If there are duplicates in the second character string, the
-last occurrence is used. If the third string is shorter than the second, its
-last character is replicated. However, if it is empty, no translation takes
-place.
-
-All character handling is done in bytes and is not UTF-8 aware.
-
-.endlist
-
-
-
-.section "Expansion operators" "SECTexpop"
-.cindex "expansion" "operators"
-For expansion items that perform transformations on a single argument string,
-the &"operator"& notation is used because it is simpler and uses fewer braces.
-The substring is first expanded before the operation is applied to it. The
-following operations can be performed:
-
-.vlist
-.vitem &*${address:*&<&'string'&>&*}*&
-.cindex "expansion" "RFC 2822 address handling"
-.cindex "&%address%& expansion item"
-The string is interpreted as an RFC 2822 address, as it might appear in a
-header line, and the effective address is extracted from it. If the string does
-not parse successfully, the result is empty.
-
-The parsing correctly handles SMTPUTF8 Unicode in the string.
-
-
-.vitem &*${addresses:*&<&'string'&>&*}*&
-.cindex "expansion" "RFC 2822 address handling"
-.cindex "&%addresses%& expansion item"
-The string (after expansion) is interpreted as a list of addresses in RFC
-2822 format, such as can be found in a &'To:'& or &'Cc:'& header line. The
-operative address (&'local-part@domain'&) is extracted from each item, and the
-result of the expansion is a colon-separated list, with appropriate
-doubling of colons should any happen to be present in the email addresses.
-Syntactically invalid RFC2822 address items are omitted from the output.
-
-It is possible to specify a character other than colon for the output
-separator by starting the string with > followed by the new separator
-character. For example:
-.code
-${addresses:>& Chief <ceo@up.stairs>, sec@base.ment (dogsbody)}
-.endd
-expands to &`ceo@up.stairs&&sec@base.ment`&. The string is expanded
-first, so if the expanded string starts with >, it may change the output
-separator unintentionally. This can be avoided by setting the output
-separator explicitly:
-.code
-${addresses:>:$h_from:}
-.endd
-
-Compare the &%address%& (singular)
-expansion item, which extracts the working address from a single RFC2822
-address. See the &%filter%&, &%map%&, and &%reduce%& items for ways of
-processing lists.
-
-To clarify "list of addresses in RFC 2822 format" mentioned above, Exim follows
-a strict interpretation of header line formatting.  Exim parses the bare,
-unquoted portion of an email address and if it finds a comma, treats it as an
-email address separator. For the example header line:
-.code
-From: =?iso-8859-2?Q?Last=2C_First?= <user@example.com>
-.endd
-The first example below demonstrates that Q-encoded email addresses are parsed
-properly if it is given the raw header (in this example, &`$rheader_from:`&).
-It does not see the comma because it's still encoded as "=2C".  The second
-example below is passed the contents of &`$header_from:`&, meaning it gets
-de-mimed. Exim sees the decoded "," so it treats it as &*two*& email addresses.
-The third example shows that the presence of a comma is skipped when it is
-quoted.  The fourth example shows SMTPUTF8 handling.
-.code
-# exim -be '${addresses:From: \
-=?iso-8859-2?Q?Last=2C_First?= <user@example.com>}'
-user@example.com
-# exim -be '${addresses:From: Last, First <user@example.com>}'
-Last:user@example.com
-# exim -be '${addresses:From: "Last, First" <user@example.com>}'
-user@example.com
-# exim -be '${addresses:フィル <フィリップ@example.jp>}'
-フィリップ@example.jp
-.endd
-
-.vitem &*${base32:*&<&'digits'&>&*}*&
-.cindex "&%base32%& expansion item"
-.cindex "expansion" "conversion to base 32"
-The string must consist entirely of decimal digits. The number is converted to
-base 32 and output as a (empty, for zero) string of characters.
-Only lowercase letters are used.
-
-.vitem &*${base32d:*&<&'base-32&~digits'&>&*}*&
-.cindex "&%base32d%& expansion item"
-.cindex "expansion" "conversion to base 32"
-The string must consist entirely of base-32 digits.
-The number is converted to decimal and output as a string.
-
-.vitem &*${base62:*&<&'digits'&>&*}*&
-.cindex "&%base62%& expansion item"
-.cindex "expansion" "conversion to base 62"
-The string must consist entirely of decimal digits. The number is converted to
-base 62 and output as a string of six characters, including leading zeros. In
-the few operating environments where Exim uses base 36 instead of base 62 for
-its message identifiers (because those systems do not have case-sensitive
-filenames), base 36 is used by this operator, despite its name. &*Note*&: Just
-to be absolutely clear: this is &'not'& base64 encoding.
-
-.vitem &*${base62d:*&<&'base-62&~digits'&>&*}*&
-.cindex "&%base62d%& expansion item"
-.cindex "expansion" "conversion to base 62"
-The string must consist entirely of base-62 digits, or, in operating
-environments where Exim uses base 36 instead of base 62 for its message
-identifiers, base-36 digits. The number is converted to decimal and output as a
-string.
-
-.vitem &*${base64:*&<&'string'&>&*}*&
-.cindex "expansion" "base64 encoding"
-.cindex "base64 encoding" "in string expansion"
-.cindex "&%base64%& expansion item"
-.cindex certificate "base64 of DER"
-This operator converts a string into one that is base64 encoded.
-
-If the string is a single variable of type certificate,
-returns the base64 encoding of the DER form of the certificate.
-
-
-.vitem &*${base64d:*&<&'string'&>&*}*&
-.cindex "expansion" "base64 decoding"
-.cindex "base64 decoding" "in string expansion"
-.cindex "&%base64d%& expansion item"
-This operator converts a base64-encoded string into the un-coded form.
-
-
-.vitem &*${domain:*&<&'string'&>&*}*&
-.cindex "domain" "extraction"
-.cindex "expansion" "domain extraction"
-The string is interpreted as an RFC 2822 address and the domain is extracted
-from it. If the string does not parse successfully, the result is empty.
-
-
-.vitem &*${escape:*&<&'string'&>&*}*&
-.cindex "expansion" "escaping non-printing characters"
-.cindex "&%escape%& expansion item"
-If the string contains any non-printing characters, they are converted to
-escape sequences starting with a backslash. Whether characters with the most
-significant bit set (so-called &"8-bit characters"&) count as printing or not
-is controlled by the &%print_topbitchars%& option.
-
-.vitem &*${escape8bit:*&<&'string'&>&*}*&
-.cindex "expansion" "escaping 8-bit characters"
-.cindex "&%escape8bit%& expansion item"
-If the string contains and characters with the most significant bit set,
-they are converted to escape sequences starting with a backslash.
-Backslashes and DEL characters are also converted.
-
-
-.vitem &*${eval:*&<&'string'&>&*}*&&~and&~&*${eval10:*&<&'string'&>&*}*&
-.cindex "expansion" "expression evaluation"
-.cindex "expansion" "arithmetic expression"
-.cindex "&%eval%& expansion item"
-These items supports simple arithmetic and bitwise logical operations in
-expansion strings. The string (after expansion) must be a conventional
-arithmetic expression, but it is limited to basic arithmetic operators, bitwise
-logical operators, and parentheses. All operations are carried out using
-integer arithmetic. The operator priorities are as follows (the same as in the
-C programming language):
-.table2 70pt 300pt
-.irow &'highest:'& "not (~), negate (-)"
-.irow ""   "multiply (*), divide (/), remainder (%)"
-.irow ""   "plus (+), minus (-)"
-.irow ""   "shift-left (<<), shift-right (>>)"
-.irow ""   "and (&&)"
-.irow ""   "xor (^)"
-.irow &'lowest:'&  "or (|)"
-.endtable
-Binary operators with the same priority are evaluated from left to right. White
-space is permitted before or after operators.
-
-For &%eval%&, numbers may be decimal, octal (starting with &"0"&) or
-hexadecimal (starting with &"0x"&). For &%eval10%&, all numbers are taken as
-decimal, even if they start with a leading zero; hexadecimal numbers are not
-permitted. This can be useful when processing numbers extracted from dates or
-times, which often do have leading zeros.
-
-A number may be followed by &"K"&, &"M"& or &"G"& to multiply it by 1024, 1024*1024
-or 1024*1024*1024,
-respectively. Negative numbers are supported. The result of the computation is
-a decimal representation of the answer (without &"K"&, &"M"& or &"G"&). For example:
-
-.display
-&`${eval:1+1}            `&  yields 2
-&`${eval:1+2*3}          `&  yields 7
-&`${eval:(1+2)*3}        `&  yields 9
-&`${eval:2+42%5}         `&  yields 4
-&`${eval:0xc&amp;5}          `&  yields 4
-&`${eval:0xc|5}          `&  yields 13
-&`${eval:0xc^5}          `&  yields 9
-&`${eval:0xc>>1}         `&  yields 6
-&`${eval:0xc<<1}         `&  yields 24
-&`${eval:~255&amp;0x1234}    `&  yields 4608
-&`${eval:-(~255&amp;0x1234)} `&  yields -4608
-.endd
-
-As a more realistic example, in an ACL you might have
-.code
-deny   message = Too many bad recipients
-       condition =                    \
-         ${if and {                   \
-           {>{$rcpt_count}{10}}       \
-           {                          \
-           <                          \
-             {$recipients_count}      \
-             {${eval:$rcpt_count/2}}  \
-           }                          \
-         }{yes}{no}}
-.endd
-The condition is true if there have been more than 10 RCPT commands and
-fewer than half of them have resulted in a valid recipient.
-
-
-.vitem &*${expand:*&<&'string'&>&*}*&
-.cindex "expansion" "re-expansion of substring"
-The &%expand%& operator causes a string to be expanded for a second time. For
-example,
-.code
-${expand:${lookup{$domain}dbm{/some/file}{$value}}}
-.endd
-first looks up a string in a file while expanding the operand for &%expand%&,
-and then re-expands what it has found.
-
-
-.vitem &*${from_utf8:*&<&'string'&>&*}*&
-.cindex "Unicode"
-.cindex "UTF-8" "conversion from"
-.cindex "expansion" "UTF-8 conversion"
-.cindex "&%from_utf8%& expansion item"
-The world is slowly moving towards Unicode, although there are no standards for
-email yet. However, other applications (including some databases) are starting
-to store data in Unicode, using UTF-8 encoding. This operator converts from a
-UTF-8 string to an ISO-8859-1 string. UTF-8 code values greater than 255 are
-converted to underscores. The input must be a valid UTF-8 string. If it is not,
-the result is an undefined sequence of bytes.
-
-Unicode code points with values less than 256 are compatible with ASCII and
-ISO-8859-1 (also known as Latin-1).
-For example, character 169 is the copyright symbol in both cases, though the
-way it is encoded is different. In UTF-8, more than one byte is needed for
-characters with code values greater than 127, whereas ISO-8859-1 is a
-single-byte encoding (but thereby limited to 256 characters). This makes
-translation from UTF-8 to ISO-8859-1 straightforward.
-
-
-.vitem &*${hash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
-.cindex "hash function" "textual"
-.cindex "expansion" "textual hash"
-The &%hash%& operator is a simpler interface to the hashing function that can
-be used when the two parameters are fixed numbers (as opposed to strings that
-change when expanded). The effect is the same as
-.code
-${hash{<n>}{<m>}{<string>}}
-.endd
-See the description of the general &%hash%& item above for details. The
-abbreviation &%h%& can be used when &%hash%& is used as an operator.
-
-
-
-.vitem &*${hex2b64:*&<&'hexstring'&>&*}*&
-.cindex "base64 encoding" "conversion from hex"
-.cindex "expansion" "hex to base64"
-.cindex "&%hex2b64%& expansion item"
-This operator converts a hex string into one that is base64 encoded. This can
-be useful for processing the output of the various hashing functions.
-
-
-
-.vitem &*${hexquote:*&<&'string'&>&*}*&
-.cindex "quoting" "hex-encoded unprintable characters"
-.cindex "&%hexquote%& expansion item"
-This operator converts non-printable characters in a string into a hex
-escape form. Byte values between 33 (!) and 126 (~) inclusive are left
-as is, and other byte values are converted to &`\xNN`&, for example, a
-byte value 127 is converted to &`\x7f`&.
-
-
-.vitem &*${ipv6denorm:*&<&'string'&>&*}*&
-.cindex "&%ipv6denorm%& expansion item"
-.cindex "IP address" normalisation
-This expands an IPv6 address to a full eight-element colon-separated set
-of hex digits including leading zeroes.
-A trailing ipv4-style dotted-decimal set is converted to hex.
-Pure IPv4 addresses are converted to IPv4-mapped IPv6.
-
-.vitem &*${ipv6norm:*&<&'string'&>&*}*&
-.cindex "&%ipv6norm%& expansion item"
-.cindex "IP address" normalisation
-.cindex "IP address" "canonical form"
-This converts an IPv6 address to canonical form.
-Leading zeroes of groups are omitted, and the longest
-set of zero-valued groups is replaced with a double colon.
-A trailing ipv4-style dotted-decimal set is converted to hex.
-Pure IPv4 addresses are converted to IPv4-mapped IPv6.
-
-
-.vitem &*${lc:*&<&'string'&>&*}*&
-.cindex "case forcing in strings"
-.cindex "string" "case forcing"
-.cindex "lower casing"
-.cindex "expansion" "case forcing"
-.cindex "&%lc%& expansion item"
-This forces the letters in the string into lower-case, for example:
-.code
-${lc:$local_part}
-.endd
-Case is defined per the system C locale.
-
-.vitem &*${length_*&<&'number'&>&*:*&<&'string'&>&*}*&
-.cindex "expansion" "string truncation"
-.cindex "&%length%& expansion item"
-The &%length%& operator is a simpler interface to the &%length%& function that
-can be used when the parameter is a fixed number (as opposed to a string that
-changes when expanded). The effect is the same as
-.code
-${length{<number>}{<string>}}
-.endd
-See the description of the general &%length%& item above for details. Note that
-&%length%& is not the same as &%strlen%&. The abbreviation &%l%& can be used
-when &%length%& is used as an operator.
-All measurement is done in bytes and is not UTF-8 aware.
-
-
-.vitem &*${listcount:*&<&'string'&>&*}*&
-.cindex "expansion" "list item count"
-.cindex "list" "item count"
-.cindex "list" "count of items"
-.cindex "&%listcount%& expansion item"
-The string is interpreted as a list and the number of items is returned.
-
-
-.vitem &*${listnamed:*&<&'name'&>&*}*&&~and&~&*${listnamed_*&<&'type'&>&*:*&<&'name'&>&*}*&
-.cindex "expansion" "named list"
-.cindex "&%listnamed%& expansion item"
-The name is interpreted as a named list and the content of the list is returned,
-expanding any referenced lists, re-quoting as needed for colon-separation.
-If the optional type is given it must be one of "a", "d", "h" or "l"
-and selects address-, domain-, host- or localpart- lists to search among respectively.
-Otherwise all types are searched in an undefined order and the first
-matching list is returned.
-
-
-.vitem &*${local_part:*&<&'string'&>&*}*&
-.cindex "expansion" "local part extraction"
-.cindex "&%local_part%& expansion item"
-The string is interpreted as an RFC 2822 address and the local part is
-extracted from it. If the string does not parse successfully, the result is
-empty.
-The parsing correctly handles SMTPUTF8 Unicode in the string.
-
-
-.vitem &*${mask:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*&
-.cindex "masked IP address"
-.cindex "IP address" "masking"
-.cindex "CIDR notation"
-.cindex "expansion" "IP address masking"
-.cindex "&%mask%& expansion item"
-If the form of the string to be operated on is not an IP address followed by a
-slash and an integer (that is, a network address in CIDR notation), the
-expansion fails. Otherwise, this operator converts the IP address to binary,
-masks off the least significant bits according to the bit count, and converts
-the result back to text, with mask appended. For example,
-.code
-${mask:10.111.131.206/28}
-.endd
-returns the string &"10.111.131.192/28"&. Since this operation is expected to
-be mostly used for looking up masked addresses in files, the result for an IPv6
-address uses dots to separate components instead of colons, because colon
-terminates a key string in lsearch files. So, for example,
-.code
-${mask:3ffe:ffff:836f:0a00:000a:0800:200a:c031/99}
-.endd
-returns the string
-.code
-3ffe.ffff.836f.0a00.000a.0800.2000.0000/99
-.endd
-Letters in IPv6 addresses are always output in lower case.
-
-
-.vitem &*${md5:*&<&'string'&>&*}*&
-.cindex "MD5 hash"
-.cindex "expansion" "MD5 hash"
-.cindex certificate fingerprint
-.cindex "&%md5%& expansion item"
-The &%md5%& operator computes the MD5 hash value of the string, and returns it
-as a 32-digit hexadecimal number, in which any letters are in lower case.
-
-If the string is a single variable of type certificate,
-returns the MD5 hash fingerprint of the certificate.
-
-
-.vitem &*${nhash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
-.cindex "expansion" "numeric hash"
-.cindex "hash function" "numeric"
-The &%nhash%& operator is a simpler interface to the numeric hashing function
-that can be used when the two parameters are fixed numbers (as opposed to
-strings that change when expanded). The effect is the same as
-.code
-${nhash{<n>}{<m>}{<string>}}
-.endd
-See the description of the general &%nhash%& item above for details.
-
-
-.vitem &*${quote:*&<&'string'&>&*}*&
-.cindex "quoting" "in string expansions"
-.cindex "expansion" "quoting"
-.cindex "&%quote%& expansion item"
-The &%quote%& operator puts its argument into double quotes if it
-is an empty string or
-contains anything other than letters, digits, underscores, dots, and hyphens.
-Any occurrences of double quotes and backslashes are escaped with a backslash.
-Newlines and carriage returns are converted to &`\n`& and &`\r`&,
-respectively For example,
-.code
-${quote:ab"*"cd}
-.endd
-becomes
-.code
-"ab\"*\"cd"
-.endd
-The place where this is useful is when the argument is a substitution from a
-variable or a message header.
-
-.vitem &*${quote_local_part:*&<&'string'&>&*}*&
-.cindex "&%quote_local_part%& expansion item"
-This operator is like &%quote%&, except that it quotes the string only if
-required to do so by the rules of RFC 2822 for quoting local parts. For
-example, a plus sign would not cause quoting (but it would for &%quote%&).
-If you are creating a new email address from the contents of &$local_part$&
-(or any other unknown data), you should always use this operator.
-
-This quoting determination is not SMTPUTF8-aware, thus quoting non-ASCII data
-will likely use the quoting form.
-Thus &'${quote_local_part:フィル}'& will always become &'"フィル"'&.
-
-
-.vitem &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*&
-.cindex "quoting" "lookup-specific"
-This operator applies lookup-specific quoting rules to the string. Each
-query-style lookup type has its own quoting rules which are described with
-the lookups in chapter &<<CHAPfdlookup>>&. For example,
-.code
-${quote_ldap:two * two}
-.endd
-returns
-.code
-two%20%5C2A%20two
-.endd
-For single-key lookup types, no quoting is ever necessary and this operator
-yields an unchanged string.
-
-
-.vitem &*${randint:*&<&'n'&>&*}*&
-.cindex "random number"
-This operator returns a somewhat random number which is less than the
-supplied number and is at least 0.  The quality of this randomness depends
-on how Exim was built; the values are not suitable for keying material.
-If Exim is linked against OpenSSL then RAND_pseudo_bytes() is used.
-If Exim is linked against GnuTLS then gnutls_rnd(GNUTLS_RND_NONCE) is used,
-for versions of GnuTLS with that function.
-Otherwise, the implementation may be arc4random(), random() seeded by
-srandomdev() or srandom(), or a custom implementation even weaker than
-random().
-
-
-.vitem &*${reverse_ip:*&<&'ipaddr'&>&*}*&
-.cindex "expansion" "IP address"
-This operator reverses an IP address; for IPv4 addresses, the result is in
-dotted-quad decimal form, while for IPv6 addresses the result is in
-dotted-nibble hexadecimal form.  In both cases, this is the "natural" form
-for DNS.  For example,
-.code
-${reverse_ip:192.0.2.4}
-${reverse_ip:2001:0db8:c42:9:1:abcd:192.0.2.127}
-.endd
-returns
-.code
-4.2.0.192
-f.7.2.0.0.0.0.c.d.c.b.a.1.0.0.0.9.0.0.0.2.4.c.0.8.b.d.0.1.0.0.2
-.endd
-
-
-.vitem &*${rfc2047:*&<&'string'&>&*}*&
-.cindex "expansion" "RFC 2047"
-.cindex "RFC 2047" "expansion operator"
-.cindex "&%rfc2047%& expansion item"
-This operator encodes text according to the rules of RFC 2047. This is an
-encoding that is used in header lines to encode non-ASCII characters. It is
-assumed that the input string is in the encoding specified by the
-&%headers_charset%& option, which gets its default at build time. If the string
-contains only characters in the range 33&--126, and no instances of the
-characters
-.code
-? = ( ) < > @ , ; : \ " . [ ] _
-.endd
-it is not modified. Otherwise, the result is the RFC 2047 encoding of the
-string, using as many &"encoded words"& as necessary to encode all the
-characters.
-
-
-.vitem &*${rfc2047d:*&<&'string'&>&*}*&
-.cindex "expansion" "RFC 2047"
-.cindex "RFC 2047" "decoding"
-.cindex "&%rfc2047d%& expansion item"
-This operator decodes strings that are encoded as per RFC 2047. Binary zero
-bytes are replaced by question marks. Characters are converted into the
-character set defined by &%headers_charset%&. Overlong RFC 2047 &"words"& are
-not recognized unless &%check_rfc2047_length%& is set false.
-
-&*Note*&: If you use &%$header%&_&'xxx'&&*:*& (or &%$h%&_&'xxx'&&*:*&) to
-access a header line, RFC 2047 decoding is done automatically. You do not need
-to use this operator as well.
-
-
-
-.vitem &*${rxquote:*&<&'string'&>&*}*&
-.cindex "quoting" "in regular expressions"
-.cindex "regular expressions" "quoting"
-.cindex "&%rxquote%& expansion item"
-The &%rxquote%& operator inserts a backslash before any non-alphanumeric
-characters in its argument. This is useful when substituting the values of
-variables or headers inside regular expressions.
-
-
-.vitem &*${sha1:*&<&'string'&>&*}*&
-.cindex "SHA-1 hash"
-.cindex "expansion" "SHA-1 hashing"
-.cindex certificate fingerprint
-.cindex "&%sha1%& expansion item"
-The &%sha1%& operator computes the SHA-1 hash value of the string, and returns
-it as a 40-digit hexadecimal number, in which any letters are in upper case.
-
-If the string is a single variable of type certificate,
-returns the SHA-1 hash fingerprint of the certificate.
-
-
-.vitem &*${sha256:*&<&'string'&>&*}*& &&&
-       &*${sha2:*&<&'string'&>&*}*& &&&
-       &*${sha2_<n>:*&<&'string'&>&*}*&
-.cindex "SHA-256 hash"
-.cindex "SHA-2 hash"
-.cindex certificate fingerprint
-.cindex "expansion" "SHA-256 hashing"
-.cindex "&%sha256%& expansion item"
-.cindex "&%sha2%& expansion item"
-The &%sha256%& operator computes the SHA-256 hash value of the string
-and returns
-it as a 64-digit hexadecimal number, in which any letters are in upper case.
-
-If the string is a single variable of type certificate,
-returns the SHA-256 hash fingerprint of the certificate.
-
-The operator can also be spelled &%sha2%& and does the same as &%sha256%&
-(except for certificates, which are not supported).
-Finally, if an underbar
-and a number is appended it specifies the output length, selecting a
-member of the SHA-2 family of hash functions.
-Values of 256, 384 and 512 are accepted, with 256 being the default.
-
-
-.vitem &*${sha3:*&<&'string'&>&*}*& &&&
-       &*${sha3_<n>:*&<&'string'&>&*}*&
-.cindex "SHA3 hash"
-.cindex "expansion" "SHA3 hashing"
-.cindex "&%sha3%& expansion item"
-The &%sha3%& operator computes the SHA3-256 hash value of the string
-and returns
-it as a 64-digit hexadecimal number, in which any letters are in upper case.
-
-If a number is appended, separated by an underbar, it specifies
-the output length.  Values of 224, 256, 384 and 512 are accepted;
-with 256 being the default.
-
-The &%sha3%& expansion item is only supported if Exim has been
-compiled with GnuTLS 3.5.0 or later,
-or OpenSSL 1.1.1 or later.
-The macro "_CRYPTO_HASH_SHA3" will be defined if it is supported.
-
-
-.vitem &*${stat:*&<&'string'&>&*}*&
-.cindex "expansion" "statting a file"
-.cindex "file" "extracting characteristics"
-.cindex "&%stat%& expansion item"
-The string, after expansion, must be a file path. A call to the &[stat()]&
-function is made for this path. If &[stat()]& fails, an error occurs and the
-expansion fails. If it succeeds, the data from the stat replaces the item, as a
-series of <&'name'&>=<&'value'&> pairs, where the values are all numerical,
-except for the value of &"smode"&. The names are: &"mode"& (giving the mode as
-a 4-digit octal number), &"smode"& (giving the mode in symbolic format as a
-10-character string, as for the &'ls'& command), &"inode"&, &"device"&,
-&"links"&, &"uid"&, &"gid"&, &"size"&, &"atime"&, &"mtime"&, and &"ctime"&. You
-can extract individual fields using the &%extract%& expansion item.
-
-The use of the &%stat%& expansion in users' filter files can be locked out by
-the system administrator. &*Warning*&: The file size may be incorrect on 32-bit
-systems for files larger than 2GB.
-
-.vitem &*${str2b64:*&<&'string'&>&*}*&
-.cindex "&%str2b64%& expansion item"
-Now deprecated, a synonym for the &%base64%& expansion operator.
-
-
-
-.vitem &*${strlen:*&<&'string'&>&*}*&
-.cindex "expansion" "string length"
-.cindex "string" "length in expansion"
-.cindex "&%strlen%& expansion item"
-The item is replace by the length of the expanded string, expressed as a
-decimal number. &*Note*&: Do not confuse &%strlen%& with &%length%&.
-All measurement is done in bytes and is not UTF-8 aware.
-
-
-.vitem &*${substr_*&<&'start'&>&*_*&<&'length'&>&*:*&<&'string'&>&*}*&
-.cindex "&%substr%& expansion item"
-.cindex "substring extraction"
-.cindex "expansion" "substring expansion"
-The &%substr%& operator is a simpler interface to the &%substr%& function that
-can be used when the two parameters are fixed numbers (as opposed to strings
-that change when expanded). The effect is the same as
-.code
-${substr{<start>}{<length>}{<string>}}
-.endd
-See the description of the general &%substr%& item above for details. The
-abbreviation &%s%& can be used when &%substr%& is used as an operator.
-All measurement is done in bytes and is not UTF-8 aware.
-
-.vitem &*${time_eval:*&<&'string'&>&*}*&
-.cindex "&%time_eval%& expansion item"
-.cindex "time interval" "decoding"
-This item converts an Exim time interval such as &`2d4h5m`& into a number of
-seconds.
-
-.vitem &*${time_interval:*&<&'string'&>&*}*&
-.cindex "&%time_interval%& expansion item"
-.cindex "time interval" "formatting"
-The argument (after sub-expansion) must be a sequence of decimal digits that
-represents an interval of time as a number of seconds. It is converted into a
-number of larger units and output in Exim's normal time format, for example,
-&`1w3d4h2m6s`&.
-
-.vitem &*${uc:*&<&'string'&>&*}*&
-.cindex "case forcing in strings"
-.cindex "string" "case forcing"
-.cindex "upper casing"
-.cindex "expansion" "case forcing"
-.cindex "&%uc%& expansion item"
-This forces the letters in the string into upper-case.
-Case is defined per the system C locale.
-
-.vitem &*${utf8clean:*&<&'string'&>&*}*&
-.cindex "correction of invalid utf-8 sequences in strings"
-.cindex "utf-8" "utf-8 sequences"
-.cindex "incorrect utf-8"
-.cindex "expansion" "utf-8 forcing"
-.cindex "&%utf8clean%& expansion item"
-This replaces any invalid utf-8 sequence in the string by the character &`?`&.
-In versions of Exim before 4.92, this did not correctly do so for a truncated
-final codepoint's encoding, and the character would be silently dropped.
-If you must handle detection of this scenario across both sets of Exim behavior,
-the complexity will depend upon the task.
-For instance, to detect if the first character is multibyte and a 1-byte
-extraction can be successfully used as a path component (as is common for
-dividing up delivery folders), you might use:
-.code
-condition = ${if inlist{${utf8clean:${length_1:$local_part}}}{:?}{yes}{no}}
-.endd
-(which will false-positive if the first character of the local part is a
-literal question mark).
-
-.vitem "&*${utf8_domain_to_alabel:*&<&'string'&>&*}*&" &&&
-       "&*${utf8_domain_from_alabel:*&<&'string'&>&*}*&" &&&
-       "&*${utf8_localpart_to_alabel:*&<&'string'&>&*}*&" &&&
-       "&*${utf8_localpart_from_alabel:*&<&'string'&>&*}*&"
-.cindex expansion UTF-8
-.cindex UTF-8 expansion
-.cindex EAI
-.cindex internationalisation
-.cindex "&%utf8_domain_to_alabel%& expansion item"
-.cindex "&%utf8_domain_from_alabel%& expansion item"
-.cindex "&%utf8_localpart_to_alabel%& expansion item"
-.cindex "&%utf8_localpart_from_alabel%& expansion item"
-These convert EAI mail name components between UTF-8 and a-label forms.
-For information on internationalisation support see &<<SECTi18nMTA>>&.
-.endlist
-
-
-
-
-
-
-.section "Expansion conditions" "SECTexpcond"
-.scindex IIDexpcond "expansion" "conditions"
-The following conditions are available for testing by the &%${if%& construct
-while expanding strings:
-
-.vlist
-.vitem &*!*&<&'condition'&>
-.cindex "expansion" "negating a condition"
-.cindex "negation" "in expansion condition"
-Preceding any condition with an exclamation mark negates the result of the
-condition.
-
-.vitem <&'symbolic&~operator'&>&~&*{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
-.cindex "numeric comparison"
-.cindex "expansion" "numeric comparison"
-There are a number of symbolic operators for doing numeric comparisons. They
-are:
-.display
-&`=   `&   equal
-&`==  `&   equal
-&`>   `&   greater
-&`>=  `&   greater or equal
-&`<   `&   less
-&`<=  `&   less or equal
-.endd
-For example:
-.code
-${if >{$message_size}{10M} ...
-.endd
-Note that the general negation operator provides for inequality testing. The
-two strings must take the form of optionally signed decimal integers,
-optionally followed by one of the letters &"K"&, &"M"& or &"G"& (in either upper or
-lower case), signifying multiplication by 1024, 1024*1024 or 1024*1024*1024, respectively.
-As a special case, the numerical value of an empty string is taken as
-zero.
-
-In all cases, a relative comparator OP is testing if <&'string1'&> OP
-<&'string2'&>; the above example is checking if &$message_size$& is larger than
-10M, not if 10M is larger than &$message_size$&.
-
-
-.vitem &*acl&~{{*&<&'name'&>&*}{*&<&'arg1'&>&*}&&&
-	{*&<&'arg2'&>&*}...}*&
-.cindex "expansion" "calling an acl"
-.cindex "&%acl%&" "expansion condition"
-The name and zero to nine argument strings are first expanded separately.  The expanded
-arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
-Any unused are made empty.  The variable &$acl_narg$& is set to the number of
-arguments.  The named ACL (see chapter &<<CHAPACL>>&) is called
-and may use the variables; if another acl expansion is used the values
-are restored after it returns.  If the ACL sets
-a value using a "message =" modifier the variable $value becomes
-the result of the expansion, otherwise it is empty.
-If the ACL returns accept the condition is true; if deny, false.
-If the ACL returns defer the result is a forced-fail.
-
-.vitem &*bool&~{*&<&'string'&>&*}*&
-.cindex "expansion" "boolean parsing"
-.cindex "&%bool%& expansion condition"
-This condition turns a string holding a true or false representation into
-a boolean state.  It parses &"true"&, &"false"&, &"yes"& and &"no"&
-(case-insensitively); also integer numbers map to true if non-zero,
-false if zero.
-An empty string is treated as false.
-Leading and trailing whitespace is ignored;
-thus a string consisting only of whitespace is false.
-All other string values will result in expansion failure.
-
-When combined with ACL variables, this expansion condition will let you
-make decisions in one place and act on those decisions in another place.
-For example:
-.code
-${if bool{$acl_m_privileged_sender} ...
-.endd
-
-
-.vitem &*bool_lax&~{*&<&'string'&>&*}*&
-.cindex "expansion" "boolean parsing"
-.cindex "&%bool_lax%& expansion condition"
-Like &%bool%&, this condition turns a string into a boolean state.  But
-where &%bool%& accepts a strict set of strings, &%bool_lax%& uses the same
-loose definition that the Router &%condition%& option uses.  The empty string
-and the values &"false"&, &"no"& and &"0"& map to false, all others map to
-true.  Leading and trailing whitespace is ignored.
-
-Note that where &"bool{00}"& is false, &"bool_lax{00}"& is true.
-
-.vitem &*crypteq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
-.cindex "expansion" "encrypted comparison"
-.cindex "encrypted strings, comparing"
-.cindex "&%crypteq%& expansion condition"
-This condition is included in the Exim binary if it is built to support any
-authentication mechanisms (see chapter &<<CHAPSMTPAUTH>>&). Otherwise, it is
-necessary to define SUPPORT_CRYPTEQ in &_Local/Makefile_& to get &%crypteq%&
-included in the binary.
-
-The &%crypteq%& condition has two arguments. The first is encrypted and
-compared against the second, which is already encrypted. The second string may
-be in the LDAP form for storing encrypted strings, which starts with the
-encryption type in curly brackets, followed by the data. If the second string
-does not begin with &"{"& it is assumed to be encrypted with &[crypt()]& or
-&[crypt16()]& (see below), since such strings cannot begin with &"{"&.
-Typically this will be a field from a password file. An example of an encrypted
-string in LDAP form is:
-.code
-{md5}CY9rzUYh03PK3k6DJie09g==
-.endd
-If such a string appears directly in an expansion, the curly brackets have to
-be quoted, because they are part of the expansion syntax. For example:
-.code
-${if crypteq {test}{\{md5\}CY9rzUYh03PK3k6DJie09g==}{yes}{no}}
-.endd
-The following encryption types (whose names are matched case-independently) are
-supported:
-
-.ilist
-.cindex "MD5 hash"
-.cindex "base64 encoding" "in encrypted password"
-&%{md5}%& computes the MD5 digest of the first string, and expresses this as
-printable characters to compare with the remainder of the second string. If the
-length of the comparison string is 24, Exim assumes that it is base64 encoded
-(as in the above example). If the length is 32, Exim assumes that it is a
-hexadecimal encoding of the MD5 digest. If the length not 24 or 32, the
-comparison fails.
-
-.next
-.cindex "SHA-1 hash"
-&%{sha1}%& computes the SHA-1 digest of the first string, and expresses this as
-printable characters to compare with the remainder of the second string. If the
-length of the comparison string is 28, Exim assumes that it is base64 encoded.
-If the length is 40, Exim assumes that it is a hexadecimal encoding of the
-SHA-1 digest. If the length is not 28 or 40, the comparison fails.
-
-.next
-.cindex "&[crypt()]&"
-&%{crypt}%& calls the &[crypt()]& function, which traditionally used to use
-only the first eight characters of the password. However, in modern operating
-systems this is no longer true, and in many cases the entire password is used,
-whatever its length.
-
-.next
-.cindex "&[crypt16()]&"
-&%{crypt16}%& calls the &[crypt16()]& function, which was originally created to
-use up to 16 characters of the password in some operating systems. Again, in
-modern operating systems, more characters may be used.
-.endlist
-Exim has its own version of &[crypt16()]&, which is just a double call to
-&[crypt()]&. For operating systems that have their own version, setting
-HAVE_CRYPT16 in &_Local/Makefile_& when building Exim causes it to use the
-operating system version instead of its own. This option is set by default in
-the OS-dependent &_Makefile_& for those operating systems that are known to
-support &[crypt16()]&.
-
-Some years after Exim's &[crypt16()]& was implemented, a user discovered that
-it was not using the same algorithm as some operating systems' versions. It
-turns out that as well as &[crypt16()]& there is a function called
-&[bigcrypt()]& in some operating systems. This may or may not use the same
-algorithm, and both of them may be different to Exim's built-in &[crypt16()]&.
-
-However, since there is now a move away from the traditional &[crypt()]&
-functions towards using SHA1 and other algorithms, tidying up this area of
-Exim is seen as very low priority.
-
-If you do not put a encryption type (in curly brackets) in a &%crypteq%&
-comparison, the default is usually either &`{crypt}`& or &`{crypt16}`&, as
-determined by the setting of DEFAULT_CRYPT in &_Local/Makefile_&. The default
-default is &`{crypt}`&. Whatever the default, you can always use either
-function by specifying it explicitly in curly brackets.
-
-.vitem &*def:*&<&'variable&~name'&>
-.cindex "expansion" "checking for empty variable"
-.cindex "&%def%& expansion condition"
-The &%def%& condition must be followed by the name of one of the expansion
-variables defined in section &<<SECTexpvar>>&. The condition is true if the
-variable does not contain the empty string. For example:
-.code
-${if def:sender_ident {from $sender_ident}}
-.endd
-Note that the variable name is given without a leading &%$%& character. If the
-variable does not exist, the expansion fails.
-
-.vitem "&*def:header_*&<&'header&~name'&>&*:*&&~&~or&~&&&
-        &~&*def:h_*&<&'header&~name'&>&*:*&"
-.cindex "expansion" "checking header line existence"
-This condition is true if a message is being processed and the named header
-exists in the message. For example,
-.code
-${if def:header_reply-to:{$h_reply-to:}{$h_from:}}
-.endd
-&*Note*&: No &%$%& appears before &%header_%& or &%h_%& in the condition, and
-the header name must be terminated by a colon if white space does not follow.
-
-.vitem &*eq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
-       &*eqi&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
-.cindex "string" "comparison"
-.cindex "expansion" "string comparison"
-.cindex "&%eq%& expansion condition"
-.cindex "&%eqi%& expansion condition"
-The two substrings are first expanded. The condition is true if the two
-resulting strings are identical. For &%eq%& the comparison includes the case of
-letters, whereas for &%eqi%& the comparison is case-independent, where
-case is defined per the system C locale.
-
-.vitem &*exists&~{*&<&'file&~name'&>&*}*&
-.cindex "expansion" "file existence test"
-.cindex "file" "existence test"
-.cindex "&%exists%&, expansion condition"
-The substring is first expanded and then interpreted as an absolute path. The
-condition is true if the named file (or directory) exists. The existence test
-is done by calling the &[stat()]& function. The use of the &%exists%& test in
-users' filter files may be locked out by the system administrator.
-
-.vitem &*first_delivery*&
-.cindex "delivery" "first"
-.cindex "first delivery"
-.cindex "expansion" "first delivery test"
-.cindex "&%first_delivery%& expansion condition"
-This condition, which has no data, is true during a message's first delivery
-attempt. It is false during any subsequent delivery attempts.
-
-
-.vitem "&*forall{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&" &&&
-       "&*forany{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&"
-.cindex "list" "iterative conditions"
-.cindex "expansion" "&*forall*& condition"
-.cindex "expansion" "&*forany*& condition"
-.vindex "&$item$&"
-These conditions iterate over a list. The first argument is expanded to form
-the list. By default, the list separator is a colon, but it can be changed by
-the normal method (&<<SECTlistsepchange>>&).
-The second argument is interpreted as a condition that is to
-be applied to each item in the list in turn. During the interpretation of the
-condition, the current list item is placed in a variable called &$item$&.
-.ilist
-For &*forany*&, interpretation stops if the condition is true for any item, and
-the result of the whole condition is true. If the condition is false for all
-items in the list, the overall condition is false.
-.next
-For &*forall*&, interpretation stops if the condition is false for any item,
-and the result of the whole condition is false. If the condition is true for
-all items in the list, the overall condition is true.
-.endlist
-Note that negation of &*forany*& means that the condition must be false for all
-items for the overall condition to succeed, and negation of &*forall*& means
-that the condition must be false for at least one item. In this example, the
-list separator is changed to a comma:
-.code
-${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}}
-.endd
-The value of &$item$& is saved and restored while &%forany%& or &%forall%& is
-being processed, to enable these expansion items to be nested.
-
-To scan a named list, expand it with the &*listnamed*& operator.
-
-.vitem "&*forall_json{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
-       "&*forany_json{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
-       "&*forall_jsons{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
-       "&*forany_jsons{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&"
-.cindex JSON "iterative conditions"
-.cindex JSON expansions
-.cindex expansion "&*forall_json*& condition"
-.cindex expansion "&*forany_json*& condition"
-.cindex expansion "&*forall_jsons*& condition"
-.cindex expansion "&*forany_jsons*& condition"
-As for the above, except that the first argument must, after expansion,
-be a JSON array.
-The array separator is not changeable.
-For the &"jsons"& variants the elements are expected to be JSON strings
-and have their quotes removed before the evaluation of the condition.
-
-
-
-.vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
-       &*gei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
-.cindex "string" "comparison"
-.cindex "expansion" "string comparison"
-.cindex "&%ge%& expansion condition"
-.cindex "&%gei%& expansion condition"
-The two substrings are first expanded. The condition is true if the first
-string is lexically greater than or equal to the second string. For &%ge%& the
-comparison includes the case of letters, whereas for &%gei%& the comparison is
-case-independent.
-Case and collation order are defined per the system C locale.
-
-.vitem &*gt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
-       &*gti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
-.cindex "string" "comparison"
-.cindex "expansion" "string comparison"
-.cindex "&%gt%& expansion condition"
-.cindex "&%gti%& expansion condition"
-The two substrings are first expanded. The condition is true if the first
-string is lexically greater than the second string. For &%gt%& the comparison
-includes the case of letters, whereas for &%gti%& the comparison is
-case-independent.
-Case and collation order are defined per the system C locale.
-
-.vitem &*inlist&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
-       &*inlisti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
-.cindex "string" "comparison"
-.cindex "list" "iterative conditions"
-Both strings are expanded; the second string is treated as a list of simple
-strings; if the first string is a member of the second, then the condition
-is true.
-For the case-independent &%inlisti%& condition, case is defined per the system C locale.
-
-These are simpler to use versions of the more powerful &*forany*& condition.
-Examples, and the &*forany*& equivalents:
-.code
-${if inlist{needle}{foo:needle:bar}}
-  ${if forany{foo:needle:bar}{eq{$item}{needle}}}
-${if inlisti{Needle}{fOo:NeeDLE:bAr}}
-  ${if forany{fOo:NeeDLE:bAr}{eqi{$item}{Needle}}}
-.endd
-
-.vitem &*isip&~{*&<&'string'&>&*}*&  &&&
-       &*isip4&~{*&<&'string'&>&*}*& &&&
-       &*isip6&~{*&<&'string'&>&*}*&
-.cindex "IP address" "testing string format"
-.cindex "string" "testing for IP address"
-.cindex "&%isip%& expansion condition"
-.cindex "&%isip4%& expansion condition"
-.cindex "&%isip6%& expansion condition"
-The substring is first expanded, and then tested to see if it has the form of
-an IP address. Both IPv4 and IPv6 addresses are valid for &%isip%&, whereas
-&%isip4%& and &%isip6%& test specifically for IPv4 or IPv6 addresses.
-
-For an IPv4 address, the test is for four dot-separated components, each of
-which consists of from one to three digits. For an IPv6 address, up to eight
-colon-separated components are permitted, each containing from one to four
-hexadecimal digits. There may be fewer than eight components if an empty
-component (adjacent colons) is present. Only one empty component is permitted.
-
-&*Note*&: The checks used to be just on the form of the address; actual numerical
-values were not considered. Thus, for example, 999.999.999.999 passed the IPv4
-check.
-This is no longer the case.
-
-The main use of these tests is to distinguish between IP addresses and
-host names, or between IPv4 and IPv6 addresses. For example, you could use
-.code
-${if isip4{$sender_host_address}...
-.endd
-to test which IP version an incoming SMTP connection is using.
-
-.vitem &*ldapauth&~{*&<&'ldap&~query'&>&*}*&
-.cindex "LDAP" "use for authentication"
-.cindex "expansion" "LDAP authentication test"
-.cindex "&%ldapauth%& expansion condition"
-This condition supports user authentication using LDAP. See section
-&<<SECTldap>>& for details of how to use LDAP in lookups and the syntax of
-queries. For this use, the query must contain a user name and password. The
-query itself is not used, and can be empty. The condition is true if the
-password is not empty, and the user name and password are accepted by the LDAP
-server. An empty password is rejected without calling LDAP because LDAP binds
-with an empty password are considered anonymous regardless of the username, and
-will succeed in most configurations. See chapter &<<CHAPSMTPAUTH>>& for details
-of SMTP authentication, and chapter &<<CHAPplaintext>>& for an example of how
-this can be used.
-
-
-.vitem &*le&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
-       &*lei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
-.cindex "string" "comparison"
-.cindex "expansion" "string comparison"
-.cindex "&%le%& expansion condition"
-.cindex "&%lei%& expansion condition"
-The two substrings are first expanded. The condition is true if the first
-string is lexically less than or equal to the second string. For &%le%& the
-comparison includes the case of letters, whereas for &%lei%& the comparison is
-case-independent.
-Case and collation order are defined per the system C locale.
-
-.vitem &*lt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
-       &*lti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
-.cindex "string" "comparison"
-.cindex "expansion" "string comparison"
-.cindex "&%lt%& expansion condition"
-.cindex "&%lti%& expansion condition"
-The two substrings are first expanded. The condition is true if the first
-string is lexically less than the second string. For &%lt%& the comparison
-includes the case of letters, whereas for &%lti%& the comparison is
-case-independent.
-Case and collation order are defined per the system C locale.
-
-
-.vitem &*match&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
-.cindex "expansion" "regular expression comparison"
-.cindex "regular expressions" "match in expanded string"
-.cindex "&%match%& expansion condition"
-The two substrings are first expanded. The second is then treated as a regular
-expression and applied to the first. Because of the pre-expansion, if the
-regular expression contains dollar, or backslash characters, they must be
-escaped. Care must also be taken if the regular expression contains braces
-(curly brackets). A closing brace must be escaped so that it is not taken as a
-premature termination of <&'string2'&>. The easiest approach is to use the
-&`\N`& feature to disable expansion of the regular expression.
-For example,
-.code
-${if match {$local_part}{\N^\d{3}\N} ...
-.endd
-If the whole expansion string is in double quotes, further escaping of
-backslashes is also required.
-
-The condition is true if the regular expression match succeeds.
-The regular expression is not required to begin with a circumflex
-metacharacter, but if there is no circumflex, the expression is not anchored,
-and it may match anywhere in the subject, not just at the start. If you want
-the pattern to match at the end of the subject, you must include the &`$`&
-metacharacter at an appropriate point.
-All character handling is done in bytes and is not UTF-8 aware,
-but we might change this in a future Exim release.
-
-.cindex "numerical variables (&$1$& &$2$& etc)" "in &%if%& expansion"
-At the start of an &%if%& expansion the values of the numeric variable
-substitutions &$1$& etc. are remembered. Obeying a &%match%& condition that
-succeeds causes them to be reset to the substrings of that condition and they
-will have these values during the expansion of the success string. At the end
-of the &%if%& expansion, the previous values are restored. After testing a
-combination of conditions using &%or%&, the subsequent values of the numeric
-variables are those of the condition that succeeded.
-
-.vitem &*match_address&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
-.cindex "&%match_address%& expansion condition"
-See &*match_local_part*&.
-
-.vitem &*match_domain&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
-.cindex "&%match_domain%& expansion condition"
-See &*match_local_part*&.
-
-.vitem &*match_ip&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
-.cindex "&%match_ip%& expansion condition"
-This condition matches an IP address to a list of IP address patterns. It must
-be followed by two argument strings. The first (after expansion) must be an IP
-address or an empty string. The second (not expanded) is a restricted host
-list that can match only an IP address, not a host name. For example:
-.code
-${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}}
-.endd
-The specific types of host list item that are permitted in the list are:
-
-.ilist
-An IP address, optionally with a CIDR mask.
-.next
-A single asterisk, which matches any IP address.
-.next
-An empty item, which matches only if the IP address is empty. This could be
-useful for testing for a locally submitted message or one from specific hosts
-in a single test such as
-. ==== As this is a nested list, any displays it contains must be indented
-. ==== as otherwise they are too far to the left. This comment applies to
-. ==== the use of xmlto plus fop. There's no problem when formatting with
-. ==== sdop, with or without the extra indent.
-.code
-  ${if match_ip{$sender_host_address}{:4.3.2.1:...}{...}{...}}
-.endd
-where the first item in the list is the empty string.
-.next
-The item @[] matches any of the local host's interface addresses.
-.next
-Single-key lookups are assumed to be like &"net-"& style lookups in host lists,
-even if &`net-`& is not specified. There is never any attempt to turn the IP
-address into a host name. The most common type of linear search for
-&*match_ip*& is likely to be &*iplsearch*&, in which the file can contain CIDR
-masks. For example:
-.code
-  ${if match_ip{$sender_host_address}{iplsearch;/some/file}...
-.endd
-It is of course possible to use other kinds of lookup, and in such a case, you
-do need to specify the &`net-`& prefix if you want to specify a specific
-address mask, for example:
-.code
-  ${if match_ip{$sender_host_address}{net24-dbm;/some/file}...
-.endd
-However, unless you are combining a &%match_ip%& condition with others, it is
-just as easy to use the fact that a lookup is itself a condition, and write:
-.code
-  ${lookup{${mask:$sender_host_address/24}}dbm{/a/file}...
-.endd
-.endlist ilist
-
-Note that <&'string2'&> is not itself subject to string expansion, unless
-Exim was built with the EXPAND_LISTMATCH_RHS option.
-
-Consult section &<<SECThoslispatip>>& for further details of these patterns.
-
-.vitem &*match_local_part&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
-.cindex "domain list" "in expansion condition"
-.cindex "address list" "in expansion condition"
-.cindex "local part" "list, in expansion condition"
-.cindex "&%match_local_part%& expansion condition"
-This condition, together with &%match_address%& and &%match_domain%&, make it
-possible to test domain, address, and local part lists within expansions. Each
-condition requires two arguments: an item and a list to match. A trivial
-example is:
-.code
-${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}}
-.endd
-In each case, the second argument may contain any of the allowable items for a
-list of the appropriate type. Also, because the second argument
-is a standard form of list, it is possible to refer to a named list.
-Thus, you can use conditions like this:
-.code
-${if match_domain{$domain}{+local_domains}{...
-.endd
-.cindex "&`+caseful`&"
-For address lists, the matching starts off caselessly, but the &`+caseful`&
-item can be used, as in all address lists, to cause subsequent items to
-have their local parts matched casefully. Domains are always matched
-caselessly.
-
-Note that <&'string2'&> is not itself subject to string expansion, unless
-Exim was built with the EXPAND_LISTMATCH_RHS option.
-
-&*Note*&: Host lists are &'not'& supported in this way. This is because
-hosts have two identities: a name and an IP address, and it is not clear
-how to specify cleanly how such a test would work. However, IP addresses can be
-matched using &%match_ip%&.
-
-.vitem &*pam&~{*&<&'string1'&>&*:*&<&'string2'&>&*:...}*&
-.cindex "PAM authentication"
-.cindex "AUTH" "with PAM"
-.cindex "Solaris" "PAM support"
-.cindex "expansion" "PAM authentication test"
-.cindex "&%pam%& expansion condition"
-&'Pluggable Authentication Modules'&
-(&url(https://mirrors.edge.kernel.org/pub/linux/libs/pam/)) are a facility that is
-available in the latest releases of Solaris and in some GNU/Linux
-distributions. The Exim support, which is intended for use in conjunction with
-the SMTP AUTH command, is available only if Exim is compiled with
-.code
-SUPPORT_PAM=yes
-.endd
-in &_Local/Makefile_&. You probably need to add &%-lpam%& to EXTRALIBS, and
-in some releases of GNU/Linux &%-ldl%& is also needed.
-
-The argument string is first expanded, and the result must be a
-colon-separated list of strings. Leading and trailing white space is ignored.
-The PAM module is initialized with the service name &"exim"& and the user name
-taken from the first item in the colon-separated data string (<&'string1'&>).
-The remaining items in the data string are passed over in response to requests
-from the authentication function. In the simple case there will only be one
-request, for a password, so the data consists of just two strings.
-
-There can be problems if any of the strings are permitted to contain colon
-characters. In the usual way, these have to be doubled to avoid being taken as
-separators. If the data is being inserted from a variable, the &%sg%& expansion
-item can be used to double any existing colons. For example, the configuration
-of a LOGIN authenticator might contain this setting:
-.code
-server_condition = ${if pam{$auth1:${sg{$auth2}{:}{::}}}}
-.endd
-For a PLAIN authenticator you could use:
-.code
-server_condition = ${if pam{$auth2:${sg{$auth3}{:}{::}}}}
-.endd
-In some operating systems, PAM authentication can be done only from a process
-running as root. Since Exim is running as the Exim user when receiving
-messages, this means that PAM cannot be used directly in those systems.
-. --- 2018-09-07: the pam_exim modified variant has gone, removed claims re using Exim via that
-
-
-.vitem &*pwcheck&~{*&<&'string1'&>&*:*&<&'string2'&>&*}*&
-.cindex "&'pwcheck'& daemon"
-.cindex "Cyrus"
-.cindex "expansion" "&'pwcheck'& authentication test"
-.cindex "&%pwcheck%& expansion condition"
-This condition supports user authentication using the Cyrus &'pwcheck'& daemon.
-This is one way of making it possible for passwords to be checked by a process
-that is not running as root. &*Note*&: The use of &'pwcheck'& is now
-deprecated. Its replacement is &'saslauthd'& (see below).
-
-The pwcheck support is not included in Exim by default. You need to specify
-the location of the pwcheck daemon's socket in &_Local/Makefile_& before
-building Exim. For example:
-.code
-CYRUS_PWCHECK_SOCKET=/var/pwcheck/pwcheck
-.endd
-You do not need to install the full Cyrus software suite in order to use
-the pwcheck daemon. You can compile and install just the daemon alone
-from the Cyrus SASL library. Ensure that &'exim'& is the only user that has
-access to the &_/var/pwcheck_& directory.
-
-The &%pwcheck%& condition takes one argument, which must be the user name and
-password, separated by a colon. For example, in a LOGIN authenticator
-configuration, you might have this:
-.code
-server_condition = ${if pwcheck{$auth1:$auth2}}
-.endd
-Again, for a PLAIN authenticator configuration, this would be:
-.code
-server_condition = ${if pwcheck{$auth2:$auth3}}
-.endd
-.vitem &*queue_running*&
-.cindex "queue runner" "detecting when delivering from"
-.cindex "expansion" "queue runner test"
-.cindex "&%queue_running%& expansion condition"
-This condition, which has no data, is true during delivery attempts that are
-initiated by queue runner processes, and false otherwise.
-
-
-.vitem &*radius&~{*&<&'authentication&~string'&>&*}*&
-.cindex "Radius"
-.cindex "expansion" "Radius authentication"
-.cindex "&%radius%& expansion condition"
-Radius authentication (RFC 2865) is supported in a similar way to PAM. You must
-set RADIUS_CONFIG_FILE in &_Local/Makefile_& to specify the location of
-the Radius client configuration file in order to build Exim with Radius
-support.
-
-With just that one setting, Exim expects to be linked with the &%radiusclient%&
-library, using the original API. If you are using release 0.4.0 or later of
-this library, you need to set
-.code
-RADIUS_LIB_TYPE=RADIUSCLIENTNEW
-.endd
-in &_Local/Makefile_& when building Exim. You can also link Exim with the
-&%libradius%& library that comes with FreeBSD. To do this, set
-.code
-RADIUS_LIB_TYPE=RADLIB
-.endd
-in &_Local/Makefile_&, in addition to setting RADIUS_CONFIGURE_FILE.
-You may also have to supply a suitable setting in EXTRALIBS so that the
-Radius library can be found when Exim is linked.
-
-The string specified by RADIUS_CONFIG_FILE is expanded and passed to the
-Radius client library, which calls the Radius server. The condition is true if
-the authentication is successful. For example:
-.code
-server_condition = ${if radius{<arguments>}}
-.endd
-
-
-.vitem "&*saslauthd&~{{*&<&'user'&>&*}{*&<&'password'&>&*}&&&
-        {*&<&'service'&>&*}{*&<&'realm'&>&*}}*&"
-.cindex "&'saslauthd'& daemon"
-.cindex "Cyrus"
-.cindex "expansion" "&'saslauthd'& authentication test"
-.cindex "&%saslauthd%& expansion condition"
-This condition supports user authentication using the Cyrus &'saslauthd'&
-daemon. This replaces the older &'pwcheck'& daemon, which is now deprecated.
-Using this daemon is one way of making it possible for passwords to be checked
-by a process that is not running as root.
-
-The saslauthd support is not included in Exim by default. You need to specify
-the location of the saslauthd daemon's socket in &_Local/Makefile_& before
-building Exim. For example:
-.code
-CYRUS_SASLAUTHD_SOCKET=/var/state/saslauthd/mux
-.endd
-You do not need to install the full Cyrus software suite in order to use
-the saslauthd daemon. You can compile and install just the daemon alone
-from the Cyrus SASL library.
-
-Up to four arguments can be supplied to the &%saslauthd%& condition, but only
-two are mandatory. For example:
-.code
-server_condition = ${if saslauthd{{$auth1}{$auth2}}}
-.endd
-The service and the realm are optional (which is why the arguments are enclosed
-in their own set of braces). For details of the meaning of the service and
-realm, and how to run the daemon, consult the Cyrus documentation.
-.endlist vlist
-
-
-
-.section "Combining expansion conditions" "SECID84"
-.cindex "expansion" "combining conditions"
-Several conditions can be tested at once by combining them using the &%and%&
-and &%or%& combination conditions. Note that &%and%& and &%or%& are complete
-conditions on their own, and precede their lists of sub-conditions. Each
-sub-condition must be enclosed in braces within the overall braces that contain
-the list. No repetition of &%if%& is used.
-
-
-.vlist
-.vitem &*or&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
-.cindex "&""or""& expansion condition"
-.cindex "expansion" "&""or""& of conditions"
-The sub-conditions are evaluated from left to right. The condition is true if
-any one of the sub-conditions is true.
-For example,
-.code
-${if or {{eq{$local_part}{spqr}}{eq{$domain}{testing.com}}}...
-.endd
-When a true sub-condition is found, the following ones are parsed but not
-evaluated. If there are several &"match"& sub-conditions the values of the
-numeric variables afterwards are taken from the first one that succeeds.
-
-.vitem &*and&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
-.cindex "&""and""& expansion condition"
-.cindex "expansion" "&""and""& of conditions"
-The sub-conditions are evaluated from left to right. The condition is true if
-all of the sub-conditions are true. If there are several &"match"&
-sub-conditions, the values of the numeric variables afterwards are taken from
-the last one. When a false sub-condition is found, the following ones are
-parsed but not evaluated.
-.endlist
-.ecindex IIDexpcond
-
-
-
-
-.section "Expansion variables" "SECTexpvar"
-.cindex "expansion" "variables, list of"
-This section contains an alphabetical list of all the expansion variables. Some
-of them are available only when Exim is compiled with specific options such as
-support for TLS or the content scanning extension.
-
-.vlist
-.vitem "&$0$&, &$1$&, etc"
-.cindex "numerical variables (&$1$& &$2$& etc)"
-When a &%match%& expansion condition succeeds, these variables contain the
-captured substrings identified by the regular expression during subsequent
-processing of the success string of the containing &%if%& expansion item.
-In the expansion condition case
-they do not retain their values afterwards; in fact, their previous
-values are restored at the end of processing an &%if%& item. The numerical
-variables may also be set externally by some other matching process which
-precedes the expansion of the string. For example, the commands available in
-Exim filter files include an &%if%& command with its own regular expression
-matching condition.
-
-.vitem "&$acl_arg1$&, &$acl_arg2$&, etc"
-Within an acl condition, expansion condition or expansion item
-any arguments are copied to these variables,
-any unused variables being made empty.
-
-.vitem "&$acl_c...$&"
-Values can be placed in these variables by the &%set%& modifier in an ACL. They
-can be given any name that starts with &$acl_c$& and is at least six characters
-long, but the sixth character must be either a digit or an underscore. For
-example: &$acl_c5$&, &$acl_c_mycount$&. The values of the &$acl_c...$&
-variables persist throughout the lifetime of an SMTP connection. They can be
-used to pass information between ACLs and between different invocations of the
-same ACL. When a message is received, the values of these variables are saved
-with the message, and can be accessed by filters, routers, and transports
-during subsequent delivery.
-
-.vitem "&$acl_m...$&"
-These variables are like the &$acl_c...$& variables, except that their values
-are reset after a message has been received. Thus, if several messages are
-received in one SMTP connection, &$acl_m...$& values are not passed on from one
-message to the next, as &$acl_c...$& values are. The &$acl_m...$& variables are
-also reset by MAIL, RSET, EHLO, HELO, and after starting a TLS session. When a
-message is received, the values of these variables are saved with the message,
-and can be accessed by filters, routers, and transports during subsequent
-delivery.
-
-.vitem &$acl_narg$&
-Within an acl condition, expansion condition or expansion item
-this variable has the number of arguments.
-
-.vitem &$acl_verify_message$&
-.vindex "&$acl_verify_message$&"
-After an address verification has failed, this variable contains the failure
-message. It retains its value for use in subsequent modifiers. The message can
-be preserved by coding like this:
-.code
-warn !verify = sender
-     set acl_m0 = $acl_verify_message
-.endd
-You can use &$acl_verify_message$& during the expansion of the &%message%& or
-&%log_message%& modifiers, to include information about the verification
-failure.
-
-.vitem &$address_data$&
-.vindex "&$address_data$&"
-This variable is set by means of the &%address_data%& option in routers. The
-value then remains with the address while it is processed by subsequent routers
-and eventually a transport. If the transport is handling multiple addresses,
-the value from the first address is used. See chapter &<<CHAProutergeneric>>&
-for more details. &*Note*&: The contents of &$address_data$& are visible in
-user filter files.
-
-If &$address_data$& is set when the routers are called from an ACL to verify
-a recipient address, the final value is still in the variable for subsequent
-conditions and modifiers of the ACL statement. If routing the address caused it
-to be redirected to just one address, the child address is also routed as part
-of the verification, and in this case the final value of &$address_data$& is
-from the child's routing.
-
-If &$address_data$& is set when the routers are called from an ACL to verify a
-sender address, the final value is also preserved, but this time in
-&$sender_address_data$&, to distinguish it from data from a recipient
-address.
-
-In both cases (recipient and sender verification), the value does not persist
-after the end of the current ACL statement. If you want to preserve
-these values for longer, you can save them in ACL variables.
-
-.vitem &$address_file$&
-.vindex "&$address_file$&"
-When, as a result of aliasing, forwarding, or filtering, a message is directed
-to a specific file, this variable holds the name of the file when the transport
-is running. At other times, the variable is empty. For example, using the
-default configuration, if user &%r2d2%& has a &_.forward_& file containing
-.code
-/home/r2d2/savemail
-.endd
-then when the &(address_file)& transport is running, &$address_file$&
-contains the text string &`/home/r2d2/savemail`&.
-.cindex "Sieve filter" "value of &$address_file$&"
-For Sieve filters, the value may be &"inbox"& or a relative folder name. It is
-then up to the transport configuration to generate an appropriate absolute path
-to the relevant file.
-
-.vitem &$address_pipe$&
-.vindex "&$address_pipe$&"
-When, as a result of aliasing or forwarding, a message is directed to a pipe,
-this variable holds the pipe command when the transport is running.
-
-.vitem "&$auth1$& &-- &$auth3$&"
-.vindex "&$auth1$&, &$auth2$&, etc"
-These variables are used in SMTP authenticators (see chapters
-&<<CHAPplaintext>>&&--&<<CHAPtlsauth>>&). Elsewhere, they are empty.
-
-.vitem &$authenticated_id$&
-.cindex "authentication" "id"
-.vindex "&$authenticated_id$&"
-When a server successfully authenticates a client it may be configured to
-preserve some of the authentication information in the variable
-&$authenticated_id$& (see chapter &<<CHAPSMTPAUTH>>&). For example, a
-user/password authenticator configuration might preserve the user name for use
-in the routers. Note that this is not the same information that is saved in
-&$sender_host_authenticated$&.
-
-When a message is submitted locally (that is, not over a TCP connection)
-the value of &$authenticated_id$& is normally the login name of the calling
-process. However, a trusted user can override this by means of the &%-oMai%&
-command line option.
-This second case also sets up information used by the
-&$authresults$& expansion item.
-
-.vitem &$authenticated_fail_id$&
-.cindex "authentication" "fail" "id"
-.vindex "&$authenticated_fail_id$&"
-When an authentication attempt fails, the variable &$authenticated_fail_id$&
-will contain the failed authentication id. If more than one authentication
-id is attempted, it will contain only the last one. The variable is
-available for processing in the ACL's, generally the quit or notquit ACL.
-A message to a local recipient could still be accepted without requiring
-authentication, which means this variable could also be visible in all of
-the ACL's as well.
-
-
-.vitem &$authenticated_sender$&
-.cindex "sender" "authenticated"
-.cindex "authentication" "sender"
-.cindex "AUTH" "on MAIL command"
-.vindex "&$authenticated_sender$&"
-When acting as a server, Exim takes note of the AUTH= parameter on an incoming
-SMTP MAIL command if it believes the sender is sufficiently trusted, as
-described in section &<<SECTauthparamail>>&. Unless the data is the string
-&"<>"&, it is set as the authenticated sender of the message, and the value is
-available during delivery in the &$authenticated_sender$& variable. If the
-sender is not trusted, Exim accepts the syntax of AUTH=, but ignores the data.
-
-.vindex "&$qualify_domain$&"
-When a message is submitted locally (that is, not over a TCP connection), the
-value of &$authenticated_sender$& is an address constructed from the login
-name of the calling process and &$qualify_domain$&, except that a trusted user
-can override this by means of the &%-oMas%& command line option.
-
-
-.vitem &$authentication_failed$&
-.cindex "authentication" "failure"
-.vindex "&$authentication_failed$&"
-This variable is set to &"1"& in an Exim server if a client issues an AUTH
-command that does not succeed. Otherwise it is set to &"0"&. This makes it
-possible to distinguish between &"did not try to authenticate"&
-(&$sender_host_authenticated$& is empty and &$authentication_failed$& is set to
-&"0"&) and &"tried to authenticate but failed"& (&$sender_host_authenticated$&
-is empty and &$authentication_failed$& is set to &"1"&). Failure includes any
-negative response to an AUTH command, including (for example) an attempt to use
-an undefined mechanism.
-
-.vitem &$av_failed$&
-.cindex "content scanning" "AV scanner failure"
-This variable is available when Exim is compiled with the content-scanning
-extension. It is set to &"0"& by default, but will be set to &"1"& if any
-problem occurs with the virus scanner (specified by &%av_scanner%&) during
-the ACL malware condition.
-
-.vitem &$body_linecount$&
-.cindex "message body" "line count"
-.cindex "body of message" "line count"
-.vindex "&$body_linecount$&"
-When a message is being received or delivered, this variable contains the
-number of lines in the message's body. See also &$message_linecount$&.
-
-.vitem &$body_zerocount$&
-.cindex "message body" "binary zero count"
-.cindex "body of message" "binary zero count"
-.cindex "binary zero" "in message body"
-.vindex "&$body_zerocount$&"
-When a message is being received or delivered, this variable contains the
-number of binary zero bytes (ASCII NULs) in the message's body.
-
-.vitem &$bounce_recipient$&
-.vindex "&$bounce_recipient$&"
-This is set to the recipient address of a bounce message while Exim is creating
-it. It is useful if a customized bounce message text file is in use (see
-chapter &<<CHAPemsgcust>>&).
-
-.vitem &$bounce_return_size_limit$&
-.vindex "&$bounce_return_size_limit$&"
-This contains the value set in the &%bounce_return_size_limit%& option, rounded
-up to a multiple of 1000. It is useful when a customized error message text
-file is in use (see chapter &<<CHAPemsgcust>>&).
-
-.vitem &$caller_gid$&
-.cindex "gid (group id)" "caller"
-.vindex "&$caller_gid$&"
-The real group id under which the process that called Exim was running. This is
-not the same as the group id of the originator of a message (see
-&$originator_gid$&). If Exim re-execs itself, this variable in the new
-incarnation normally contains the Exim gid.
-
-.vitem &$caller_uid$&
-.cindex "uid (user id)" "caller"
-.vindex "&$caller_uid$&"
-The real user id under which the process that called Exim was running. This is
-not the same as the user id of the originator of a message (see
-&$originator_uid$&). If Exim re-execs itself, this variable in the new
-incarnation normally contains the Exim uid.
-
-.vitem &$callout_address$&
-.vindex "&$callout_address$&"
-After a callout for verification, spamd or malware daemon service, the
-address that was connected to.
-
-.vitem &$compile_number$&
-.vindex "&$compile_number$&"
-The building process for Exim keeps a count of the number
-of times it has been compiled. This serves to distinguish different
-compilations of the same version of Exim.
-
-.vitem &$config_dir$&
-.vindex "&$config_dir$&"
-The directory name of the main configuration file. That is, the content of
-&$config_file$& with the last component stripped. The value does not
-contain the trailing slash. If &$config_file$& does not contain a slash,
-&$config_dir$& is ".".
-
-.vitem &$config_file$&
-.vindex "&$config_file$&"
-The name of the main configuration file Exim is using.
-
-.vitem &$dmarc_domain_policy$& &&&
-       &$dmarc_status$& &&&
-       &$dmarc_status_text$& &&&
-       &$dmarc_used_domains$&
-Results of DMARC verification.
-For details see section &<<SECDMARC>>&.
-
-.vitem &$dkim_verify_status$&
-Results of DKIM verification.
-For details see section &<<SECDKIMVFY>>&.
-
-.vitem &$dkim_cur_signer$& &&&
-       &$dkim_verify_reason$& &&&
-       &$dkim_domain$& &&&
-       &$dkim_identity$& &&&
-       &$dkim_selector$& &&&
-       &$dkim_algo$& &&&
-       &$dkim_canon_body$& &&&
-       &$dkim_canon_headers$& &&&
-       &$dkim_copiedheaders$& &&&
-       &$dkim_bodylength$& &&&
-       &$dkim_created$& &&&
-       &$dkim_expires$& &&&
-       &$dkim_headernames$& &&&
-       &$dkim_key_testing$& &&&
-       &$dkim_key_nosubdomains$& &&&
-       &$dkim_key_srvtype$& &&&
-       &$dkim_key_granularity$& &&&
-       &$dkim_key_notes$& &&&
-       &$dkim_key_length$&
-These variables are only available within the DKIM ACL.
-For details see section &<<SECDKIMVFY>>&.
-
-.vitem &$dkim_signers$&
-.vindex &$dkim_signers$&
-When a message has been received this variable contains
-a colon-separated list of signer domains and identities for the message.
-For details see section &<<SECDKIMVFY>>&.
-
-.vitem &$dnslist_domain$& &&&
-       &$dnslist_matched$& &&&
-       &$dnslist_text$& &&&
-       &$dnslist_value$&
-.vindex "&$dnslist_domain$&"
-.vindex "&$dnslist_matched$&"
-.vindex "&$dnslist_text$&"
-.vindex "&$dnslist_value$&"
-.cindex "black list (DNS)"
-When a DNS (black) list lookup succeeds, these variables are set to contain
-the following data from the lookup: the list's domain name, the key that was
-looked up, the contents of any associated TXT record, and the value from the
-main A record. See section &<<SECID204>>& for more details.
-
-.vitem &$domain$&
-.vindex "&$domain$&"
-When an address is being routed, or delivered on its own, this variable
-contains the domain. Uppercase letters in the domain are converted into lower
-case for &$domain$&.
-
-Global address rewriting happens when a message is received, so the value of
-&$domain$& during routing and delivery is the value after rewriting. &$domain$&
-is set during user filtering, but not during system filtering, because a
-message may have many recipients and the system filter is called just once.
-
-When more than one address is being delivered at once (for example, several
-RCPT commands in one SMTP delivery), &$domain$& is set only if they all
-have the same domain. Transports can be restricted to handling only one domain
-at a time if the value of &$domain$& is required at transport time &-- this is
-the default for local transports. For further details of the environment in
-which local transports are run, see chapter &<<CHAPenvironment>>&.
-
-.oindex "&%delay_warning_condition%&"
-At the end of a delivery, if all deferred addresses have the same domain, it is
-set in &$domain$& during the expansion of &%delay_warning_condition%&.
-
-The &$domain$& variable is also used in some other circumstances:
-
-.ilist
-When an ACL is running for a RCPT command, &$domain$& contains the domain of
-the recipient address. The domain of the &'sender'& address is in
-&$sender_address_domain$& at both MAIL time and at RCPT time. &$domain$& is not
-normally set during the running of the MAIL ACL. However, if the sender address
-is verified with a callout during the MAIL ACL, the sender domain is placed in
-&$domain$& during the expansions of &%hosts%&, &%interface%&, and &%port%& in
-the &(smtp)& transport.
-
-.next
-When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
-&$domain$& contains the domain portion of the address that is being rewritten;
-it can be used in the expansion of the replacement address, for example, to
-rewrite domains by file lookup.
-
-.next
-With one important exception, whenever a domain list is being scanned,
-&$domain$& contains the subject domain. &*Exception*&: When a domain list in
-a &%sender_domains%& condition in an ACL is being processed, the subject domain
-is in &$sender_address_domain$& and not in &$domain$&. It works this way so
-that, in a RCPT ACL, the sender domain list can be dependent on the
-recipient domain (which is what is in &$domain$& at this time).
-
-.next
-.cindex "ETRN" "value of &$domain$&"
-.oindex "&%smtp_etrn_command%&"
-When the &%smtp_etrn_command%& option is being expanded, &$domain$& contains
-the complete argument of the ETRN command (see section &<<SECTETRN>>&).
-.endlist
-
-.new
-.cindex "tainted data"
-If the origin of the data is an incoming message,
-the result of expanding this variable is tainted.
-See also &$domain_verified$&.
-.wen
-
-
-.vitem &$domain_data$&
-.vindex "&$domain_data$&"
-When the &%domains%& option on a router matches a domain by
-means of a lookup, the data read by the lookup is available during the running
-of the router as &$domain_data$&. In addition, if the driver routes the
-address to a transport, the value is available in that transport. If the
-transport is handling multiple addresses, the value from the first address is
-used.
-
-&$domain_data$& is also set when the &%domains%& condition in an ACL matches a
-domain by means of a lookup. The data read by the lookup is available during
-the rest of the ACL statement. In all other situations, this variable expands
-to nothing.
-
-.vitem &$exim_gid$&
-.vindex "&$exim_gid$&"
-This variable contains the numerical value of the Exim group id.
-
-.vitem &$exim_path$&
-.vindex "&$exim_path$&"
-This variable contains the path to the Exim binary.
-
-.vitem &$exim_uid$&
-.vindex "&$exim_uid$&"
-This variable contains the numerical value of the Exim user id.
-
-.vitem &$exim_version$&
-.vindex "&$exim_version$&"
-This variable contains the version string of the Exim build.
-The first character is a major version number, currently 4.
-Then after a dot, the next group of digits is a minor version number.
-There may be other characters following the minor version.
-This value may be overridden by the &%exim_version%& main config option.
-
-.vitem &$header_$&<&'name'&>
-This is not strictly an expansion variable. It is expansion syntax for
-inserting the message header line with the given name. Note that the name must
-be terminated by colon or white space, because it may contain a wide variety of
-characters. Note also that braces must &'not'& be used.
-See the full description in section &<<SECTexpansionitems>>& above.
-
-.vitem &$headers_added$&
-.vindex "&$headers_added$&"
-Within an ACL this variable contains the headers added so far by
-the ACL modifier add_header (section &<<SECTaddheadacl>>&).
-The headers are a newline-separated list.
-
-.vitem &$home$&
-.vindex "&$home$&"
-When the &%check_local_user%& option is set for a router, the user's home
-directory is placed in &$home$& when the check succeeds. In particular, this
-means it is set during the running of users' filter files. A router may also
-explicitly set a home directory for use by a transport; this can be overridden
-by a setting on the transport itself.
-
-When running a filter test via the &%-bf%& option, &$home$& is set to the value
-of the environment variable HOME, which is subject to the
-&%keep_environment%& and &%add_environment%& main config options.
-
-.vitem &$host$&
-.vindex "&$host$&"
-If a router assigns an address to a transport (any transport), and passes a
-list of hosts with the address, the value of &$host$& when the transport starts
-to run is the name of the first host on the list. Note that this applies both
-to local and remote transports.
-
-.cindex "transport" "filter"
-.cindex "filter" "transport filter"
-For the &(smtp)& transport, if there is more than one host, the value of
-&$host$& changes as the transport works its way through the list. In
-particular, when the &(smtp)& transport is expanding its options for encryption
-using TLS, or for specifying a transport filter (see chapter
-&<<CHAPtransportgeneric>>&), &$host$& contains the name of the host to which it
-is connected.
-
-When used in the client part of an authenticator configuration (see chapter
-&<<CHAPSMTPAUTH>>&), &$host$& contains the name of the server to which the
-client is connected.
-
-
-.vitem &$host_address$&
-.vindex "&$host_address$&"
-This variable is set to the remote host's IP address whenever &$host$& is set
-for a remote connection. It is also set to the IP address that is being checked
-when the &%ignore_target_hosts%& option is being processed.
-
-.vitem &$host_data$&
-.vindex "&$host_data$&"
-If a &%hosts%& condition in an ACL is satisfied by means of a lookup, the
-result of the lookup is made available in the &$host_data$& variable. This
-allows you, for example, to do things like this:
-.code
-deny  hosts = net-lsearch;/some/file
-message = $host_data
-.endd
-.vitem &$host_lookup_deferred$&
-.cindex "host name" "lookup, failure of"
-.vindex "&$host_lookup_deferred$&"
-This variable normally contains &"0"&, as does &$host_lookup_failed$&. When a
-message comes from a remote host and there is an attempt to look up the host's
-name from its IP address, and the attempt is not successful, one of these
-variables is set to &"1"&.
-
-.ilist
-If the lookup receives a definite negative response (for example, a DNS lookup
-succeeded, but no records were found), &$host_lookup_failed$& is set to &"1"&.
-
-.next
-If there is any kind of problem during the lookup, such that Exim cannot
-tell whether or not the host name is defined (for example, a timeout for a DNS
-lookup), &$host_lookup_deferred$& is set to &"1"&.
-.endlist ilist
-
-Looking up a host's name from its IP address consists of more than just a
-single reverse lookup. Exim checks that a forward lookup of at least one of the
-names it receives from a reverse lookup yields the original IP address. If this
-is not the case, Exim does not accept the looked up name(s), and
-&$host_lookup_failed$& is set to &"1"&. Thus, being able to find a name from an
-IP address (for example, the existence of a PTR record in the DNS) is not
-sufficient on its own for the success of a host name lookup. If the reverse
-lookup succeeds, but there is a lookup problem such as a timeout when checking
-the result, the name is not accepted, and &$host_lookup_deferred$& is set to
-&"1"&. See also &$sender_host_name$&.
-
-.cindex authentication "expansion item"
-Performing these checks sets up information used by the
-&%authresults%& expansion item.
-
-
-.vitem &$host_lookup_failed$&
-.vindex "&$host_lookup_failed$&"
-See &$host_lookup_deferred$&.
-
-.vitem &$host_port$&
-.vindex "&$host_port$&"
-This variable is set to the remote host's TCP port whenever &$host$& is set
-for an outbound connection.
-
-.vitem &$initial_cwd$&
-.vindex "&$initial_cwd$&
-This variable contains the full path name of the initial working
-directory of the current Exim process. This may differ from the current
-working directory, as Exim changes this to "/" during early startup, and
-to &$spool_directory$& later.
-
-.vitem &$inode$&
-.vindex "&$inode$&"
-The only time this variable is set is while expanding the &%directory_file%&
-option in the &(appendfile)& transport. The variable contains the inode number
-of the temporary file which is about to be renamed. It can be used to construct
-a unique name for the file.
-
-.vitem &$interface_address$&
-.vindex "&$interface_address$&"
-This is an obsolete name for &$received_ip_address$&.
-
-.vitem &$interface_port$&
-.vindex "&$interface_port$&"
-This is an obsolete name for &$received_port$&.
-
-.vitem &$item$&
-.vindex "&$item$&"
-This variable is used during the expansion of &*forall*& and &*forany*&
-conditions (see section &<<SECTexpcond>>&), and &*filter*&, &*map*&, and
-&*reduce*& items (see section &<<SECTexpcond>>&). In other circumstances, it is
-empty.
-
-.vitem &$ldap_dn$&
-.vindex "&$ldap_dn$&"
-This variable, which is available only when Exim is compiled with LDAP support,
-contains the DN from the last entry in the most recently successful LDAP
-lookup.
-
-.vitem &$load_average$&
-.vindex "&$load_average$&"
-This variable contains the system load average, multiplied by 1000 so that it
-is an integer. For example, if the load average is 0.21, the value of the
-variable is 210. The value is recomputed every time the variable is referenced.
-
-.vitem &$local_part$&
-.vindex "&$local_part$&"
-When an address is being routed, or delivered on its own, this
-variable contains the local part. When a number of addresses are being
-delivered together (for example, multiple RCPT commands in an SMTP
-session), &$local_part$& is not set.
-
-Global address rewriting happens when a message is received, so the value of
-&$local_part$& during routing and delivery is the value after rewriting.
-&$local_part$& is set during user filtering, but not during system filtering,
-because a message may have many recipients and the system filter is called just
-once.
-
-.new
-.cindex "tainted data"
-If the origin of the data is an incoming message,
-the result of expanding this variable is tainted.
-
-&*Warning*&: the content of this variable is usually provided by a potential
-attacker.
-Consider carefully the implications of using it unvalidated as a name
-for file access.
-This presents issues for users' &_.forward_& and filter files.
-For traditional full user accounts, use &%check_local_users%& and the
-&$local_part_verified$& variable rather than this one.
-For virtual users, store a suitable pathname component in the database
-which is used for account name validation, and use that retrieved value
-rather than this variable.
-If needed, use a router &%address_data%& or &%set%& option for
-the retrieved data.
-.wen
-
-.vindex "&$local_part_prefix$&"
-.vindex "&$local_part_prefix_v$&"
-.vindex "&$local_part_suffix$&"
-.vindex "&$local_part_suffix_v$&"
-.cindex affix variables
-If a local part prefix or suffix has been recognized, it is not included in the
-value of &$local_part$& during routing and subsequent delivery. The values of
-any prefix or suffix are in &$local_part_prefix$& and
-&$local_part_suffix$&, respectively.
-.new
-If the affix specification included a wildcard then the portion of
-the affix matched by the wildcard is in
-&$local_part_prefix_v$& or &$local_part_suffix_v$& as appropriate.
-.wen
-
-When a message is being delivered to a file, pipe, or autoreply transport as a
-result of aliasing or forwarding, &$local_part$& is set to the local part of
-the parent address, not to the filename or command (see &$address_file$& and
-&$address_pipe$&).
-
-When an ACL is running for a RCPT command, &$local_part$& contains the
-local part of the recipient address.
-
-When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
-&$local_part$& contains the local part of the address that is being rewritten;
-it can be used in the expansion of the replacement address, for example.
-
-In all cases, all quoting is removed from the local part. For example, for both
-the addresses
-.code
-"abc:xyz"@test.example
-abc\:xyz@test.example
-.endd
-the value of &$local_part$& is
-.code
-abc:xyz
-.endd
-If you use &$local_part$& to create another address, you should always wrap it
-inside a quoting operator. For example, in a &(redirect)& router you could
-have:
-.code
-data = ${quote_local_part:$local_part}@new.domain.example
-.endd
-&*Note*&: The value of &$local_part$& is normally lower cased. If you want
-to process local parts in a case-dependent manner in a router, you can set the
-&%caseful_local_part%& option (see chapter &<<CHAProutergeneric>>&).
-
-.vitem &$local_part_data$&
-.vindex "&$local_part_data$&"
-When the &%local_parts%& option on a router matches a local part by means of a
-lookup, the data read by the lookup is available during the running of the
-router as &$local_part_data$&. In addition, if the driver routes the address
-to a transport, the value is available in that transport. If the transport is
-handling multiple addresses, the value from the first address is used.
-
-&$local_part_data$& is also set when the &%local_parts%& condition in an ACL
-matches a local part by means of a lookup. The data read by the lookup is
-available during the rest of the ACL statement. In all other situations, this
-variable expands to nothing.
-
-.vitem &$local_part_prefix$&
-.vindex "&$local_part_prefix$&"
-.cindex affix variables
-When an address is being routed or delivered, and a
-specific prefix for the local part was recognized, it is available in this
-variable, having been removed from &$local_part$&.
-
-.new
-.vitem &$local_part_prefix_v$&
-.vindex "&$local_part_prefix_v$&"
-When &$local_part_prefix$& is valid and the prefix match used a wildcard,
-the portion matching the wildcard is available in this variable.
-.wen
-
-.vitem &$local_part_suffix$&
-.vindex "&$local_part_suffix$&"
-When an address is being routed or delivered, and a
-specific suffix for the local part was recognized, it is available in this
-variable, having been removed from &$local_part$&.
-
-.new
-.vitem &$local_part_suffix_v$&
-.vindex "&$local_part_suffix_v$&"
-When &$local_part_suffix$& is valid and the suffix match used a wildcard,
-the portion matching the wildcard is available in this variable.
-.wen
-
-.new
-.vitem &$local_part_verified$&
-.vindex "&$local_part_verified$&"
-If the router generic option &%check_local_part%& has run successfully,
-this variable has the user database version of &$local_part$&.
-Such values are not tainted and hence usable for building file names.
-.wen
-
-.vitem &$local_scan_data$&
-.vindex "&$local_scan_data$&"
-This variable contains the text returned by the &[local_scan()]& function when
-a message is received. See chapter &<<CHAPlocalscan>>& for more details.
-
-.vitem &$local_user_gid$&
-.vindex "&$local_user_gid$&"
-See &$local_user_uid$&.
-
-.vitem &$local_user_uid$&
-.vindex "&$local_user_uid$&"
-This variable and &$local_user_gid$& are set to the uid and gid after the
-&%check_local_user%& router precondition succeeds. This means that their values
-are available for the remaining preconditions (&%senders%&, &%require_files%&,
-and &%condition%&), for the &%address_data%& expansion, and for any
-router-specific expansions. At all other times, the values in these variables
-are &`(uid_t)(-1)`& and &`(gid_t)(-1)`&, respectively.
-
-.vitem &$localhost_number$&
-.vindex "&$localhost_number$&"
-This contains the expanded value of the
-&%localhost_number%& option. The expansion happens after the main options have
-been read.
-
-.vitem &$log_inodes$&
-.vindex "&$log_inodes$&"
-The number of free inodes in the disk partition where Exim's
-log files are being written. The value is recalculated whenever the variable is
-referenced. If the relevant file system does not have the concept of inodes,
-the value of is -1. See also the &%check_log_inodes%& option.
-
-.vitem &$log_space$&
-.vindex "&$log_space$&"
-The amount of free space (as a number of kilobytes) in the disk
-partition where Exim's log files are being written. The value is recalculated
-whenever the variable is referenced. If the operating system does not have the
-ability to find the amount of free space (only true for experimental systems),
-the space value is -1. See also the &%check_log_space%& option.
-
-
-.vitem &$lookup_dnssec_authenticated$&
-.vindex "&$lookup_dnssec_authenticated$&"
-This variable is set after a DNS lookup done by
-a dnsdb lookup expansion, dnslookup router or smtp transport.
-.cindex "DNS" "DNSSEC"
-It will be empty if &(DNSSEC)& was not requested,
-&"no"& if the result was not labelled as authenticated data
-and &"yes"& if it was.
-Results that are labelled as authoritative answer that match
-the &%dns_trust_aa%& configuration variable count also
-as authenticated data.
-
-.vitem &$mailstore_basename$&
-.vindex "&$mailstore_basename$&"
-This variable is set only when doing deliveries in &"mailstore"& format in the
-&(appendfile)& transport. During the expansion of the &%mailstore_prefix%&,
-&%mailstore_suffix%&, &%message_prefix%&, and &%message_suffix%& options, it
-contains the basename of the files that are being written, that is, the name
-without the &".tmp"&, &".env"&, or &".msg"& suffix. At all other times, this
-variable is empty.
-
-.vitem &$malware_name$&
-.vindex "&$malware_name$&"
-This variable is available when Exim is compiled with the
-content-scanning extension. It is set to the name of the virus that was found
-when the ACL &%malware%& condition is true (see section &<<SECTscanvirus>>&).
-
-.vitem &$max_received_linelength$&
-.vindex "&$max_received_linelength$&"
-.cindex "maximum" "line length"
-.cindex "line length" "maximum"
-This variable contains the number of bytes in the longest line that was
-received as part of the message, not counting the line termination
-character(s).
-It is not valid if the &%spool_files_wireformat%& option is used.
-
-.vitem &$message_age$&
-.cindex "message" "age of"
-.vindex "&$message_age$&"
-This variable is set at the start of a delivery attempt to contain the number
-of seconds since the message was received. It does not change during a single
-delivery attempt.
-
-.vitem &$message_body$&
-.cindex "body of message" "expansion variable"
-.cindex "message body" "in expansion"
-.cindex "binary zero" "in message body"
-.vindex "&$message_body$&"
-.oindex "&%message_body_visible%&"
-This variable contains the initial portion of a message's body while it is
-being delivered, and is intended mainly for use in filter files. The maximum
-number of characters of the body that are put into the variable is set by the
-&%message_body_visible%& configuration option; the default is 500.
-
-.oindex "&%message_body_newlines%&"
-By default, newlines are converted into spaces in &$message_body$&, to make it
-easier to search for phrases that might be split over a line break. However,
-this can be disabled by setting &%message_body_newlines%& to be true. Binary
-zeros are always converted into spaces.
-
-.vitem &$message_body_end$&
-.cindex "body of message" "expansion variable"
-.cindex "message body" "in expansion"
-.vindex "&$message_body_end$&"
-This variable contains the final portion of a message's
-body while it is being delivered. The format and maximum size are as for
-&$message_body$&.
-
-.vitem &$message_body_size$&
-.cindex "body of message" "size"
-.cindex "message body" "size"
-.vindex "&$message_body_size$&"
-When a message is being delivered, this variable contains the size of the body
-in bytes. The count starts from the character after the blank line that
-separates the body from the header. Newlines are included in the count. See
-also &$message_size$&, &$body_linecount$&, and &$body_zerocount$&.
-
-If the spool file is wireformat
-(see the &%spool_files_wireformat%& main option)
-the CRLF line-terminators are included in the count.
-
-.vitem &$message_exim_id$&
-.vindex "&$message_exim_id$&"
-When a message is being received or delivered, this variable contains the
-unique message id that is generated and used by Exim to identify the message.
-An id is not created for a message until after its header has been successfully
-received. &*Note*&: This is &'not'& the contents of the &'Message-ID:'& header
-line; it is the local id that Exim assigns to the message, for example:
-&`1BXTIK-0001yO-VA`&.
-
-.vitem &$message_headers$&
-.vindex &$message_headers$&
-This variable contains a concatenation of all the header lines when a message
-is being processed, except for lines added by routers or transports. The header
-lines are separated by newline characters. Their contents are decoded in the
-same way as a header line that is inserted by &%bheader%&.
-
-.vitem &$message_headers_raw$&
-.vindex &$message_headers_raw$&
-This variable is like &$message_headers$& except that no processing of the
-contents of header lines is done.
-
-.vitem &$message_id$&
-This is an old name for &$message_exim_id$&. It is now deprecated.
-
-.vitem &$message_linecount$&
-.vindex "&$message_linecount$&"
-This variable contains the total number of lines in the header and body of the
-message. Compare &$body_linecount$&, which is the count for the body only.
-During the DATA and content-scanning ACLs, &$message_linecount$& contains the
-number of lines received. Before delivery happens (that is, before filters,
-routers, and transports run) the count is increased to include the
-&'Received:'& header line that Exim standardly adds, and also any other header
-lines that are added by ACLs. The blank line that separates the message header
-from the body is not counted.
-
-As with the special case of &$message_size$&, during the expansion of the
-appendfile transport's maildir_tag option in maildir format, the value of
-&$message_linecount$& is the precise size of the number of newlines in the
-file that has been written (minus one for the blank line between the
-header and the body).
-
-Here is an example of the use of this variable in a DATA ACL:
-.code
-deny message   = Too many lines in message header
-     condition = \
-      ${if <{250}{${eval:$message_linecount - $body_linecount}}}
-.endd
-In the MAIL and RCPT ACLs, the value is zero because at that stage the
-message has not yet been received.
-
-This variable is not valid if the &%spool_files_wireformat%& option is used.
-
-.vitem &$message_size$&
-.cindex "size" "of message"
-.cindex "message" "size"
-.vindex "&$message_size$&"
-When a message is being processed, this variable contains its size in bytes. In
-most cases, the size includes those headers that were received with the
-message, but not those (such as &'Envelope-to:'&) that are added to individual
-deliveries as they are written. However, there is one special case: during the
-expansion of the &%maildir_tag%& option in the &(appendfile)& transport while
-doing a delivery in maildir format, the value of &$message_size$& is the
-precise size of the file that has been written. See also
-&$message_body_size$&, &$body_linecount$&, and &$body_zerocount$&.
-
-.cindex "RCPT" "value of &$message_size$&"
-While running a per message ACL (mail/rcpt/predata), &$message_size$&
-contains the size supplied on the MAIL command, or -1 if no size was given. The
-value may not, of course, be truthful.
-
-.vitem &$mime_$&&'xxx'&
-A number of variables whose names start with &$mime$& are
-available when Exim is compiled with the content-scanning extension. For
-details, see section &<<SECTscanmimepart>>&.
-
-.vitem "&$n0$& &-- &$n9$&"
-These variables are counters that can be incremented by means
-of the &%add%& command in filter files.
-
-.vitem &$original_domain$&
-.vindex "&$domain$&"
-.vindex "&$original_domain$&"
-When a top-level address is being processed for delivery, this contains the
-same value as &$domain$&. However, if a &"child"& address (for example,
-generated by an alias, forward, or filter file) is being processed, this
-variable contains the domain of the original address (lower cased). This
-differs from &$parent_domain$& only when there is more than one level of
-aliasing or forwarding. When more than one address is being delivered in a
-single transport run, &$original_domain$& is not set.
-
-If a new address is created by means of a &%deliver%& command in a system
-filter, it is set up with an artificial &"parent"& address. This has the local
-part &'system-filter'& and the default qualify domain.
-
-.vitem &$original_local_part$&
-.vindex "&$local_part$&"
-.vindex "&$original_local_part$&"
-When a top-level address is being processed for delivery, this contains the
-same value as &$local_part$&, unless a prefix or suffix was removed from the
-local part, because &$original_local_part$& always contains the full local
-part. When a &"child"& address (for example, generated by an alias, forward, or
-filter file) is being processed, this variable contains the full local part of
-the original address.
-
-If the router that did the redirection processed the local part
-case-insensitively, the value in &$original_local_part$& is in lower case.
-This variable differs from &$parent_local_part$& only when there is more than
-one level of aliasing or forwarding. When more than one address is being
-delivered in a single transport run, &$original_local_part$& is not set.
-
-If a new address is created by means of a &%deliver%& command in a system
-filter, it is set up with an artificial &"parent"& address. This has the local
-part &'system-filter'& and the default qualify domain.
-
-.vitem &$originator_gid$&
-.cindex "gid (group id)" "of originating user"
-.cindex "sender" "gid"
-.vindex "&$caller_gid$&"
-.vindex "&$originator_gid$&"
-This variable contains the value of &$caller_gid$& that was set when the
-message was received. For messages received via the command line, this is the
-gid of the sending user. For messages received by SMTP over TCP/IP, this is
-normally the gid of the Exim user.
-
-.vitem &$originator_uid$&
-.cindex "uid (user id)" "of originating user"
-.cindex "sender" "uid"
-.vindex "&$caller_uid$&"
-.vindex "&$originator_uid$&"
-The value of &$caller_uid$& that was set when the message was received. For
-messages received via the command line, this is the uid of the sending user.
-For messages received by SMTP over TCP/IP, this is normally the uid of the Exim
-user.
-
-.vitem &$parent_domain$&
-.vindex "&$parent_domain$&"
-This variable is similar to &$original_domain$& (see
-above), except that it refers to the immediately preceding parent address.
-
-.vitem &$parent_local_part$&
-.vindex "&$parent_local_part$&"
-This variable is similar to &$original_local_part$&
-(see above), except that it refers to the immediately preceding parent address.
-
-.vitem &$pid$&
-.cindex "pid (process id)" "of current process"
-.vindex "&$pid$&"
-This variable contains the current process id.
-
-.vitem &$pipe_addresses$&
-.cindex "filter" "transport filter"
-.cindex "transport" "filter"
-.vindex "&$pipe_addresses$&"
-This is not an expansion variable, but is mentioned here because the string
-&`$pipe_addresses`& is handled specially in the command specification for the
-&(pipe)& transport (chapter &<<CHAPpipetransport>>&) and in transport filters
-(described under &%transport_filter%& in chapter &<<CHAPtransportgeneric>>&).
-It cannot be used in general expansion strings, and provokes an &"unknown
-variable"& error if encountered.
-
-.vitem &$primary_hostname$&
-.vindex "&$primary_hostname$&"
-This variable contains the value set by &%primary_hostname%& in the
-configuration file, or read by the &[uname()]& function. If &[uname()]& returns
-a single-component name, Exim calls &[gethostbyname()]& (or
-&[getipnodebyname()]& where available) in an attempt to acquire a fully
-qualified host name. See also &$smtp_active_hostname$&.
-
-
-.vitem &$proxy_external_address$& &&&
-       &$proxy_external_port$& &&&
-       &$proxy_local_address$& &&&
-       &$proxy_local_port$& &&&
-       &$proxy_session$&
-These variables are only available when built with Proxy Protocol
-or SOCKS5 support.
-For details see chapter &<<SECTproxyInbound>>&.
-
-.vitem &$prdr_requested$&
-.cindex "PRDR" "variable for"
-This variable is set to &"yes"& if PRDR was requested by the client for the
-current message, otherwise &"no"&.
-
-.vitem &$prvscheck_address$&
-This variable is used in conjunction with the &%prvscheck%& expansion item,
-which is described in sections &<<SECTexpansionitems>>& and
-&<<SECTverifyPRVS>>&.
-
-.vitem &$prvscheck_keynum$&
-This variable is used in conjunction with the &%prvscheck%& expansion item,
-which is described in sections &<<SECTexpansionitems>>& and
-&<<SECTverifyPRVS>>&.
-
-.vitem &$prvscheck_result$&
-This variable is used in conjunction with the &%prvscheck%& expansion item,
-which is described in sections &<<SECTexpansionitems>>& and
-&<<SECTverifyPRVS>>&.
-
-.vitem &$qualify_domain$&
-.vindex "&$qualify_domain$&"
-The value set for the &%qualify_domain%& option in the configuration file.
-
-.vitem &$qualify_recipient$&
-.vindex "&$qualify_recipient$&"
-The value set for the &%qualify_recipient%& option in the configuration file,
-or if not set, the value of &$qualify_domain$&.
-
-.vitem &$queue_name$&
-.vindex &$queue_name$&
-.cindex "named queues" variable
-.cindex queues named
-The name of the spool queue in use; empty for the default queue.
-
-.vitem &$queue_size$&
-.vindex "&$queue_size$&"
-.cindex "queue" "size of"
-.cindex "spool" "number of messages"
-This variable contains the number of messages queued.
-It is evaluated on demand, but no more often than once every minute.
-
-.vitem &$r_...$&
-.vindex &$r_...$&
-.cindex router variables
-Values can be placed in these variables by the &%set%& option of a router.
-They can be given any name that starts with &$r_$&.
-The values persist for the address being handled through subsequent routers
-and the eventual transport.
-
-.vitem &$rcpt_count$&
-.vindex "&$rcpt_count$&"
-When a message is being received by SMTP, this variable contains the number of
-RCPT commands received for the current message. If this variable is used in a
-RCPT ACL, its value includes the current command.
-
-.vitem &$rcpt_defer_count$&
-.vindex "&$rcpt_defer_count$&"
-.cindex "4&'xx'& responses" "count of"
-When a message is being received by SMTP, this variable contains the number of
-RCPT commands in the current message that have previously been rejected with a
-temporary (4&'xx'&) response.
-
-.vitem &$rcpt_fail_count$&
-.vindex "&$rcpt_fail_count$&"
-When a message is being received by SMTP, this variable contains the number of
-RCPT commands in the current message that have previously been rejected with a
-permanent (5&'xx'&) response.
-
-.vitem &$received_count$&
-.vindex "&$received_count$&"
-This variable contains the number of &'Received:'& header lines in the message,
-including the one added by Exim (so its value is always greater than zero). It
-is available in the DATA ACL, the non-SMTP ACL, and while routing and
-delivering.
-
-.vitem &$received_for$&
-.vindex "&$received_for$&"
-If there is only a single recipient address in an incoming message, this
-variable contains that address when the &'Received:'& header line is being
-built. The value is copied after recipient rewriting has happened, but before
-the &[local_scan()]& function is run.
-
-.vitem &$received_ip_address$&
-.vindex "&$received_ip_address$&"
-As soon as an Exim server starts processing an incoming TCP/IP connection, this
-variable is set to the address of the local IP interface, and &$received_port$&
-is set to the local port number. (The remote IP address and port are in
-&$sender_host_address$& and &$sender_host_port$&.) When testing with &%-bh%&,
-the port value is -1 unless it has been set using the &%-oMi%& command line
-option.
-
-As well as being useful in ACLs (including the &"connect"& ACL), these variable
-could be used, for example, to make the filename for a TLS certificate depend
-on which interface and/or port is being used for the incoming connection. The
-values of &$received_ip_address$& and &$received_port$& are saved with any
-messages that are received, thus making these variables available at delivery
-time.
-For outbound connections see &$sending_ip_address$&.
-
-.vitem &$received_port$&
-.vindex "&$received_port$&"
-See &$received_ip_address$&.
-
-.vitem &$received_protocol$&
-.vindex "&$received_protocol$&"
-When a message is being processed, this variable contains the name of the
-protocol by which it was received. Most of the names used by Exim are defined
-by RFCs 821, 2821, and 3848. They start with &"smtp"& (the client used HELO) or
-&"esmtp"& (the client used EHLO). This can be followed by &"s"& for secure
-(encrypted) and/or &"a"& for authenticated. Thus, for example, if the protocol
-is set to &"esmtpsa"&, the message was received over an encrypted SMTP
-connection and the client was successfully authenticated.
-
-Exim uses the protocol name &"smtps"& for the case when encryption is
-automatically set up on connection without the use of STARTTLS (see
-&%tls_on_connect_ports%&), and the client uses HELO to initiate the
-encrypted SMTP session. The name &"smtps"& is also used for the rare situation
-where the client initially uses EHLO, sets up an encrypted connection using
-STARTTLS, and then uses HELO afterwards.
-
-The &%-oMr%& option provides a way of specifying a custom protocol name for
-messages that are injected locally by trusted callers. This is commonly used to
-identify messages that are being re-injected after some kind of scanning.
-
-.vitem &$received_time$&
-.vindex "&$received_time$&"
-This variable contains the date and time when the current message was received,
-as a number of seconds since the start of the Unix epoch.
-
-.vitem &$recipient_data$&
-.vindex "&$recipient_data$&"
-This variable is set after an indexing lookup success in an ACL &%recipients%&
-condition. It contains the data from the lookup, and the value remains set
-until the next &%recipients%& test. Thus, you can do things like this:
-.display
-&`require recipients  = cdb*@;/some/file`&
-&`deny    `&&'some further test involving'& &`$recipient_data`&
-.endd
-&*Warning*&: This variable is set only when a lookup is used as an indexing
-method in the address list, using the semicolon syntax as in the example above.
-The variable is not set for a lookup that is used as part of the string
-expansion that all such lists undergo before being interpreted.
-
-.vitem &$recipient_verify_failure$&
-.vindex "&$recipient_verify_failure$&"
-In an ACL, when a recipient verification fails, this variable contains
-information about the failure. It is set to one of the following words:
-
-.ilist
-&"qualify"&: The address was unqualified (no domain), and the message
-was neither local nor came from an exempted host.
-
-.next
-&"route"&: Routing failed.
-
-.next
-&"mail"&: Routing succeeded, and a callout was attempted; rejection occurred at
-or before the MAIL command (that is, on initial connection, HELO, or
-MAIL).
-
-.next
-&"recipient"&: The RCPT command in a callout was rejected.
-.next
-
-&"postmaster"&: The postmaster check in a callout was rejected.
-.endlist
-
-The main use of this variable is expected to be to distinguish between
-rejections of MAIL and rejections of RCPT.
-
-.vitem &$recipients$&
-.vindex "&$recipients$&"
-This variable contains a list of envelope recipients for a message. A comma and
-a space separate the addresses in the replacement text. However, the variable
-is not generally available, to prevent exposure of Bcc recipients in
-unprivileged users' filter files. You can use &$recipients$& only in these
-cases:
-
-.olist
-In a system filter file.
-.next
-In the ACLs associated with the DATA command and with non-SMTP messages, that
-is, the ACLs defined by &%acl_smtp_predata%&, &%acl_smtp_data%&,
-&%acl_smtp_mime%&, &%acl_not_smtp_start%&, &%acl_not_smtp%&, and
-&%acl_not_smtp_mime%&.
-.next
-From within a &[local_scan()]& function.
-.endlist
-
-
-.vitem &$recipients_count$&
-.vindex "&$recipients_count$&"
-When a message is being processed, this variable contains the number of
-envelope recipients that came with the message. Duplicates are not excluded
-from the count. While a message is being received over SMTP, the number
-increases for each accepted recipient. It can be referenced in an ACL.
-
-
-.vitem &$regex_match_string$&
-.vindex "&$regex_match_string$&"
-This variable is set to contain the matching regular expression after a
-&%regex%& ACL condition has matched (see section &<<SECTscanregex>>&).
-
-.vitem "&$regex1$&, &$regex2$&, etc"
-.cindex "regex submatch variables (&$1regex$& &$2regex$& etc)"
-When a &%regex%& or &%mime_regex%& ACL condition succeeds,
-these variables contain the
-captured substrings identified by the regular expression.
-
-
-.vitem &$reply_address$&
-.vindex "&$reply_address$&"
-When a message is being processed, this variable contains the contents of the
-&'Reply-To:'& header line if one exists and it is not empty, or otherwise the
-contents of the &'From:'& header line. Apart from the removal of leading
-white space, the value is not processed in any way. In particular, no RFC 2047
-decoding or character code translation takes place.
-
-.vitem &$return_path$&
-.vindex "&$return_path$&"
-When a message is being delivered, this variable contains the return path &--
-the sender field that will be sent as part of the envelope. It is not enclosed
-in <> characters. At the start of routing an address, &$return_path$& has the
-same value as &$sender_address$&, but if, for example, an incoming message to a
-mailing list has been expanded by a router which specifies a different address
-for bounce messages, &$return_path$& subsequently contains the new bounce
-address, whereas &$sender_address$& always contains the original sender address
-that was received with the message. In other words, &$sender_address$& contains
-the incoming envelope sender, and &$return_path$& contains the outgoing
-envelope sender.
-
-.vitem &$return_size_limit$&
-.vindex "&$return_size_limit$&"
-This is an obsolete name for &$bounce_return_size_limit$&.
-
-.vitem &$router_name$&
-.cindex "router" "name"
-.cindex "name" "of router"
-.vindex "&$router_name$&"
-During the running of a router this variable contains its name.
-
-.vitem &$runrc$&
-.cindex "return code" "from &%run%& expansion"
-.vindex "&$runrc$&"
-This variable contains the return code from a command that is run by the
-&%${run...}%& expansion item. &*Warning*&: In a router or transport, you cannot
-assume the order in which option values are expanded, except for those
-preconditions whose order of testing is documented. Therefore, you cannot
-reliably expect to set &$runrc$& by the expansion of one option, and use it in
-another.
-
-.vitem &$self_hostname$&
-.oindex "&%self%&" "value of host name"
-.vindex "&$self_hostname$&"
-When an address is routed to a supposedly remote host that turns out to be the
-local host, what happens is controlled by the &%self%& generic router option.
-One of its values causes the address to be passed to another router. When this
-happens, &$self_hostname$& is set to the name of the local host that the
-original router encountered. In other circumstances its contents are null.
-
-.vitem &$sender_address$&
-.vindex "&$sender_address$&"
-When a message is being processed, this variable contains the sender's address
-that was received in the message's envelope. The case of letters in the address
-is retained, in both the local part and the domain. For bounce messages, the
-value of this variable is the empty string. See also &$return_path$&.
-
-.vitem &$sender_address_data$&
-.vindex "&$address_data$&"
-.vindex "&$sender_address_data$&"
-If &$address_data$& is set when the routers are called from an ACL to verify a
-sender address, the final value is preserved in &$sender_address_data$&, to
-distinguish it from data from a recipient address. The value does not persist
-after the end of the current ACL statement. If you want to preserve it for
-longer, you can save it in an ACL variable.
-
-.vitem &$sender_address_domain$&
-.vindex "&$sender_address_domain$&"
-The domain portion of &$sender_address$&.
-
-.vitem &$sender_address_local_part$&
-.vindex "&$sender_address_local_part$&"
-The local part portion of &$sender_address$&.
-
-.vitem &$sender_data$&
-.vindex "&$sender_data$&"
-This variable is set after a lookup success in an ACL &%senders%& condition or
-in a router &%senders%& option. It contains the data from the lookup, and the
-value remains set until the next &%senders%& test. Thus, you can do things like
-this:
-.display
-&`require senders      = cdb*@;/some/file`&
-&`deny    `&&'some further test involving'& &`$sender_data`&
-.endd
-&*Warning*&: This variable is set only when a lookup is used as an indexing
-method in the address list, using the semicolon syntax as in the example above.
-The variable is not set for a lookup that is used as part of the string
-expansion that all such lists undergo before being interpreted.
-
-.vitem &$sender_fullhost$&
-.vindex "&$sender_fullhost$&"
-When a message is received from a remote host, this variable contains the host
-name and IP address in a single string. It ends with the IP address in square
-brackets, followed by a colon and a port number if the logging of ports is
-enabled. The format of the rest of the string depends on whether the host
-issued a HELO or EHLO SMTP command, and whether the host name was verified by
-looking up its IP address. (Looking up the IP address can be forced by the
-&%host_lookup%& option, independent of verification.) A plain host name at the
-start of the string is a verified host name; if this is not present,
-verification either failed or was not requested. A host name in parentheses is
-the argument of a HELO or EHLO command. This is omitted if it is identical to
-the verified host name or to the host's IP address in square brackets.
-
-.vitem &$sender_helo_dnssec$&
-.vindex "&$sender_helo_dnssec$&"
-This boolean variable is true if a successful HELO verification was
-.cindex "DNS" "DNSSEC"
-done using DNS information the resolver library stated was authenticated data.
-
-.vitem &$sender_helo_name$&
-.vindex "&$sender_helo_name$&"
-When a message is received from a remote host that has issued a HELO or EHLO
-command, the argument of that command is placed in this variable. It is also
-set if HELO or EHLO is used when a message is received using SMTP locally via
-the &%-bs%& or &%-bS%& options.
-
-.vitem &$sender_host_address$&
-.vindex "&$sender_host_address$&"
-When a message is received from a remote host using SMTP,
-this variable contains that
-host's IP address. For locally non-SMTP submitted messages, it is empty.
-
-.vitem &$sender_host_authenticated$&
-.vindex "&$sender_host_authenticated$&"
-This variable contains the name (not the public name) of the authenticator
-driver that successfully authenticated the client from which the message was
-received. It is empty if there was no successful authentication. See also
-&$authenticated_id$&.
-
-.vitem &$sender_host_dnssec$&
-.vindex "&$sender_host_dnssec$&"
-If an attempt to populate &$sender_host_name$& has been made
-(by reference, &%hosts_lookup%& or
-otherwise) then this boolean will have been set true if, and only if, the
-resolver library states that both
-the reverse and forward DNS were authenticated data.  At all
-other times, this variable is false.
-
-.cindex "DNS" "DNSSEC"
-It is likely that you will need to coerce DNSSEC support on in the resolver
-library, by setting:
-.code
-dns_dnssec_ok = 1
-.endd
-
-Exim does not perform DNSSEC validation itself, instead leaving that to a
-validating resolver (e.g. unbound, or bind with suitable configuration).
-
-If you have changed &%host_lookup_order%& so that &`bydns`& is not the first
-mechanism in the list, then this variable will be false.
-
-This requires that your system resolver library support EDNS0 (and that
-DNSSEC flags exist in the system headers).  If the resolver silently drops
-all EDNS0 options, then this will have no effect.  OpenBSD's asr resolver
-is known to currently ignore EDNS0, documented in CAVEATS of asr_run(3).
-
-
-.vitem &$sender_host_name$&
-.vindex "&$sender_host_name$&"
-When a message is received from a remote host, this variable contains the
-host's name as obtained by looking up its IP address. For messages received by
-other means, this variable is empty.
-
-.vindex "&$host_lookup_failed$&"
-If the host name has not previously been looked up, a reference to
-&$sender_host_name$& triggers a lookup (for messages from remote hosts).
-A looked up name is accepted only if it leads back to the original IP address
-via a forward lookup. If either the reverse or the forward lookup fails to find
-any data, or if the forward lookup does not yield the original IP address,
-&$sender_host_name$& remains empty, and &$host_lookup_failed$& is set to &"1"&.
-
-.vindex "&$host_lookup_deferred$&"
-However, if either of the lookups cannot be completed (for example, there is a
-DNS timeout), &$host_lookup_deferred$& is set to &"1"&, and
-&$host_lookup_failed$& remains set to &"0"&.
-
-Once &$host_lookup_failed$& is set to &"1"&, Exim does not try to look up the
-host name again if there is a subsequent reference to &$sender_host_name$&
-in the same Exim process, but it does try again if &$host_lookup_deferred$&
-is set to &"1"&.
-
-Exim does not automatically look up every calling host's name. If you want
-maximum efficiency, you should arrange your configuration so that it avoids
-these lookups altogether. The lookup happens only if one or more of the
-following are true:
-
-.ilist
-A string containing &$sender_host_name$& is expanded.
-.next
-The calling host matches the list in &%host_lookup%&. In the default
-configuration, this option is set to *, so it must be changed if lookups are
-to be avoided. (In the code, the default for &%host_lookup%& is unset.)
-.next
-Exim needs the host name in order to test an item in a host list. The items
-that require this are described in sections &<<SECThoslispatnam>>& and
-&<<SECThoslispatnamsk>>&.
-.next
-The calling host matches &%helo_try_verify_hosts%& or &%helo_verify_hosts%&.
-In this case, the host name is required to compare with the name quoted in any
-EHLO or HELO commands that the client issues.
-.next
-The remote host issues a EHLO or HELO command that quotes one of the
-domains in &%helo_lookup_domains%&. The default value of this option is
-. ==== As this is a nested list, any displays it contains must be indented
-. ==== as otherwise they are too far to the left.
-.code
-  helo_lookup_domains = @ : @[]
-.endd
-which causes a lookup if a remote host (incorrectly) gives the server's name or
-IP address in an EHLO or HELO command.
-.endlist
-
-
-.vitem &$sender_host_port$&
-.vindex "&$sender_host_port$&"
-When a message is received from a remote host, this variable contains the port
-number that was used on the remote host.
-
-.vitem &$sender_ident$&
-.vindex "&$sender_ident$&"
-When a message is received from a remote host, this variable contains the
-identification received in response to an RFC 1413 request. When a message has
-been received locally, this variable contains the login name of the user that
-called Exim.
-
-.vitem &$sender_rate_$&&'xxx'&
-A number of variables whose names begin &$sender_rate_$& are set as part of the
-&%ratelimit%& ACL condition. Details are given in section
-&<<SECTratelimiting>>&.
-
-.vitem &$sender_rcvhost$&
-.cindex "DNS" "reverse lookup"
-.cindex "reverse DNS lookup"
-.vindex "&$sender_rcvhost$&"
-This is provided specifically for use in &'Received:'& headers. It starts with
-either the verified host name (as obtained from a reverse DNS lookup) or, if
-there is no verified host name, the IP address in square brackets. After that
-there may be text in parentheses. When the first item is a verified host name,
-the first thing in the parentheses is the IP address in square brackets,
-followed by a colon and a port number if port logging is enabled. When the
-first item is an IP address, the port is recorded as &"port=&'xxxx'&"& inside
-the parentheses.
-
-There may also be items of the form &"helo=&'xxxx'&"& if HELO or EHLO
-was used and its argument was not identical to the real host name or IP
-address, and &"ident=&'xxxx'&"& if an RFC 1413 ident string is available. If
-all three items are present in the parentheses, a newline and tab are inserted
-into the string, to improve the formatting of the &'Received:'& header.
-
-.vitem &$sender_verify_failure$&
-.vindex "&$sender_verify_failure$&"
-In an ACL, when a sender verification fails, this variable contains information
-about the failure. The details are the same as for
-&$recipient_verify_failure$&.
-
-.vitem &$sending_ip_address$&
-.vindex "&$sending_ip_address$&"
-This variable is set whenever an outgoing SMTP connection to another host has
-been set up. It contains the IP address of the local interface that is being
-used. This is useful if a host that has more than one IP address wants to take
-on different personalities depending on which one is being used. For incoming
-connections, see &$received_ip_address$&.
-
-.vitem &$sending_port$&
-.vindex "&$sending_port$&"
-This variable is set whenever an outgoing SMTP connection to another host has
-been set up. It contains the local port that is being used. For incoming
-connections, see &$received_port$&.
-
-.vitem &$smtp_active_hostname$&
-.vindex "&$smtp_active_hostname$&"
-During an incoming SMTP session, this variable contains the value of the active
-host name, as specified by the &%smtp_active_hostname%& option. The value of
-&$smtp_active_hostname$& is saved with any message that is received, so its
-value can be consulted during routing and delivery.
-
-.vitem &$smtp_command$&
-.vindex "&$smtp_command$&"
-During the processing of an incoming SMTP command, this variable contains the
-entire command. This makes it possible to distinguish between HELO and EHLO in
-the HELO ACL, and also to distinguish between commands such as these:
-.code
-MAIL FROM:<>
-MAIL FROM: <>
-.endd
-For a MAIL command, extra parameters such as SIZE can be inspected. For a RCPT
-command, the address in &$smtp_command$& is the original address before any
-rewriting, whereas the values in &$local_part$& and &$domain$& are taken from
-the address after SMTP-time rewriting.
-
-.vitem &$smtp_command_argument$&
-.cindex "SMTP" "command, argument for"
-.vindex "&$smtp_command_argument$&"
-While an ACL is running to check an SMTP command, this variable contains the
-argument, that is, the text that follows the command name, with leading white
-space removed. Following the introduction of &$smtp_command$&, this variable is
-somewhat redundant, but is retained for backwards compatibility.
-
-.vitem &$smtp_command_history$&
-.cindex SMTP "command history"
-.vindex "&$smtp_command_history$&"
-A comma-separated list (with no whitespace) of the most-recent SMTP commands
-received, in time-order left to right.  Only a limited number of commands
-are remembered.
-
-.vitem &$smtp_count_at_connection_start$&
-.vindex "&$smtp_count_at_connection_start$&"
-This variable is set greater than zero only in processes spawned by the Exim
-daemon for handling incoming SMTP connections. The name is deliberately long,
-in order to emphasize what the contents are. When the daemon accepts a new
-connection, it increments this variable. A copy of the variable is passed to
-the child process that handles the connection, but its value is fixed, and
-never changes. It is only an approximation of how many incoming connections
-there actually are, because many other connections may come and go while a
-single connection is being processed. When a child process terminates, the
-daemon decrements its copy of the variable.
-
-.vitem "&$sn0$& &-- &$sn9$&"
-These variables are copies of the values of the &$n0$& &-- &$n9$& accumulators
-that were current at the end of the system filter file. This allows a system
-filter file to set values that can be tested in users' filter files. For
-example, a system filter could set a value indicating how likely it is that a
-message is junk mail.
-
-.vitem &$spam_$&&'xxx'&
-A number of variables whose names start with &$spam$& are available when Exim
-is compiled with the content-scanning extension. For details, see section
-&<<SECTscanspamass>>&.
-
-.vitem &$spf_header_comment$& &&&
-       &$spf_received$& &&&
-       &$spf_result$& &&&
-       &$spf_result_guessed$& &&&
-       &$spf_smtp_comment$&
-These variables are only available if Exim is built with SPF support.
-For details see section &<<SECSPF>>&.
-
-.vitem &$spool_directory$&
-.vindex "&$spool_directory$&"
-The name of Exim's spool directory.
-
-.vitem &$spool_inodes$&
-.vindex "&$spool_inodes$&"
-The number of free inodes in the disk partition where Exim's spool files are
-being written. The value is recalculated whenever the variable is referenced.
-If the relevant file system does not have the concept of inodes, the value of
-is -1. See also the &%check_spool_inodes%& option.
-
-.vitem &$spool_space$&
-.vindex "&$spool_space$&"
-The amount of free space (as a number of kilobytes) in the disk partition where
-Exim's spool files are being written. The value is recalculated whenever the
-variable is referenced. If the operating system does not have the ability to
-find the amount of free space (only true for experimental systems), the space
-value is -1. For example, to check in an ACL that there is at least 50
-megabytes free on the spool, you could write:
-.code
-condition = ${if > {$spool_space}{50000}}
-.endd
-See also the &%check_spool_space%& option.
-
-
-.vitem &$thisaddress$&
-.vindex "&$thisaddress$&"
-This variable is set only during the processing of the &%foranyaddress%&
-command in a filter file. Its use is explained in the description of that
-command, which can be found in the separate document entitled &'Exim's
-interfaces to mail filtering'&.
-
-.vitem &$tls_in_bits$&
-.vindex "&$tls_in_bits$&"
-Contains an approximation of the TLS cipher's bit-strength
-on the inbound connection; the meaning of
-this depends upon the TLS implementation used.
-If TLS has not been negotiated, the value will be 0.
-The value of this is automatically fed into the Cyrus SASL authenticator
-when acting as a server, to specify the "external SSF" (a SASL term).
-
-The deprecated &$tls_bits$& variable refers to the inbound side
-except when used in the context of an outbound SMTP delivery, when it refers to
-the outbound.
-
-.vitem &$tls_out_bits$&
-.vindex "&$tls_out_bits$&"
-Contains an approximation of the TLS cipher's bit-strength
-on an outbound SMTP connection; the meaning of
-this depends upon the TLS implementation used.
-If TLS has not been negotiated, the value will be 0.
-
-.vitem &$tls_in_ourcert$&
-.vindex "&$tls_in_ourcert$&"
-.cindex certificate variables
-This variable refers to the certificate presented to the peer of an
-inbound connection when the message was received.
-It is only useful as the argument of a
-&%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
-or a &%def%& condition.
-
-&*Note*&: Under versions of OpenSSL preceding 1.1.1,
-when a list of more than one
-file is used for &%tls_certificate%&, this variable is not reliable.
-The macro "_TLS_BAD_MULTICERT_IN_OURCERT" will be defined for those versions.
-
-.vitem &$tls_in_peercert$&
-.vindex "&$tls_in_peercert$&"
-This variable refers to the certificate presented by the peer of an
-inbound connection when the message was received.
-It is only useful as the argument of a
-&%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
-or a &%def%& condition.
-If certificate verification fails it may refer to a failing chain element
-which is not the leaf.
-
-.vitem &$tls_out_ourcert$&
-.vindex "&$tls_out_ourcert$&"
-This variable refers to the certificate presented to the peer of an
-outbound connection.  It is only useful as the argument of a
-&%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
-or a &%def%& condition.
-
-.vitem &$tls_out_peercert$&
-.vindex "&$tls_out_peercert$&"
-This variable refers to the certificate presented by the peer of an
-outbound connection.  It is only useful as the argument of a
-&%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
-or a &%def%& condition.
-If certificate verification fails it may refer to a failing chain element
-which is not the leaf.
-
-.vitem &$tls_in_certificate_verified$&
-.vindex "&$tls_in_certificate_verified$&"
-This variable is set to &"1"& if a TLS certificate was verified when the
-message was received, and &"0"& otherwise.
-
-The deprecated &$tls_certificate_verified$& variable refers to the inbound side
-except when used in the context of an outbound SMTP delivery, when it refers to
-the outbound.
-
-.vitem &$tls_out_certificate_verified$&
-.vindex "&$tls_out_certificate_verified$&"
-This variable is set to &"1"& if a TLS certificate was verified when an
-outbound SMTP connection was made,
-and &"0"& otherwise.
-
-.vitem &$tls_in_cipher$&
-.vindex "&$tls_in_cipher$&"
-.vindex "&$tls_cipher$&"
-When a message is received from a remote host over an encrypted SMTP
-connection, this variable is set to the cipher suite that was negotiated, for
-example DES-CBC3-SHA. In other circumstances, in particular, for message
-received over unencrypted connections, the variable is empty. Testing
-&$tls_in_cipher$& for emptiness is one way of distinguishing between encrypted and
-non-encrypted connections during ACL processing.
-
-The deprecated &$tls_cipher$& variable is the same as &$tls_in_cipher$& during message reception,
-but in the context of an outward SMTP delivery taking place via the &(smtp)& transport
-becomes the same as &$tls_out_cipher$&.
-
-.vitem &$tls_in_cipher_std$&
-.vindex "&$tls_in_cipher_std$&"
-As above, but returning the RFC standard name for the cipher suite.
-
-.vitem &$tls_out_cipher$&
-.vindex "&$tls_out_cipher$&"
-This variable is
-cleared before any outgoing SMTP connection is made,
-and then set to the outgoing cipher suite if one is negotiated. See chapter
-&<<CHAPTLS>>& for details of TLS support and chapter &<<CHAPsmtptrans>>& for
-details of the &(smtp)& transport.
-
-.vitem &$tls_out_cipher_std$&
-.vindex "&$tls_out_cipher_std$&"
-As above, but returning the RFC standard name for the cipher suite.
-
-.vitem &$tls_out_dane$&
-.vindex &$tls_out_dane$&
-DANE active status.  See section &<<SECDANE>>&.
-
-.vitem &$tls_in_ocsp$&
-.vindex "&$tls_in_ocsp$&"
-When a message is received from a remote client connection
-the result of any OCSP request from the client is encoded in this variable:
-.code
-0 OCSP proof was not requested (default value)
-1 No response to request
-2 Response not verified
-3 Verification failed
-4 Verification succeeded
-.endd
-
-.vitem &$tls_out_ocsp$&
-.vindex "&$tls_out_ocsp$&"
-When a message is sent to a remote host connection
-the result of any OCSP request made is encoded in this variable.
-See &$tls_in_ocsp$& for values.
-
-.vitem &$tls_in_peerdn$&
-.vindex "&$tls_in_peerdn$&"
-.vindex "&$tls_peerdn$&"
-.cindex certificate "extracting fields"
-When a message is received from a remote host over an encrypted SMTP
-connection, and Exim is configured to request a certificate from the client,
-the value of the Distinguished Name of the certificate is made available in the
-&$tls_in_peerdn$& during subsequent processing.
-If certificate verification fails it may refer to a failing chain element
-which is not the leaf.
-
-The deprecated &$tls_peerdn$& variable refers to the inbound side
-except when used in the context of an outbound SMTP delivery, when it refers to
-the outbound.
-
-.vitem &$tls_out_peerdn$&
-.vindex "&$tls_out_peerdn$&"
-When a message is being delivered to a remote host over an encrypted SMTP
-connection, and Exim is configured to request a certificate from the server,
-the value of the Distinguished Name of the certificate is made available in the
-&$tls_out_peerdn$& during subsequent processing.
-If certificate verification fails it may refer to a failing chain element
-which is not the leaf.
-
-.vitem &$tls_in_sni$&
-.vindex "&$tls_in_sni$&"
-.vindex "&$tls_sni$&"
-.cindex "TLS" "Server Name Indication"
-When a TLS session is being established, if the client sends the Server
-Name Indication extension, the value will be placed in this variable.
-If the variable appears in &%tls_certificate%& then this option and
-some others, described in &<<SECTtlssni>>&,
-will be re-expanded early in the TLS session, to permit
-a different certificate to be presented (and optionally a different key to be
-used) to the client, based upon the value of the SNI extension.
-
-The deprecated &$tls_sni$& variable refers to the inbound side
-except when used in the context of an outbound SMTP delivery, when it refers to
-the outbound.
-
-.vitem &$tls_out_sni$&
-.vindex "&$tls_out_sni$&"
-.cindex "TLS" "Server Name Indication"
-During outbound
-SMTP deliveries, this variable reflects the value of the &%tls_sni%& option on
-the transport.
-
-.vitem &$tls_out_tlsa_usage$&
-.vindex &$tls_out_tlsa_usage$&
-Bitfield of TLSA record types found.  See section &<<SECDANE>>&.
-
-.vitem &$tls_in_ver$&
-.vindex "&$tls_in_ver$&"
-When a message is received from a remote host over an encrypted SMTP connection
-this variable is set to the protocol version, eg &'TLS1.2'&.
-
-.vitem &$tls_out_ver$&
-.vindex "&$tls_out_ver$&"
-When a message is being delivered to a remote host over an encrypted SMTP connection
-this variable is set to the protocol version.
-
-
-.vitem &$tod_bsdinbox$&
-.vindex "&$tod_bsdinbox$&"
-The time of day and the date, in the format required for BSD-style mailbox
-files, for example: Thu Oct 17 17:14:09 1995.
-
-.vitem &$tod_epoch$&
-.vindex "&$tod_epoch$&"
-The time and date as a number of seconds since the start of the Unix epoch.
-
-.vitem &$tod_epoch_l$&
-.vindex "&$tod_epoch_l$&"
-The time and date as a number of microseconds since the start of the Unix epoch.
-
-.vitem &$tod_full$&
-.vindex "&$tod_full$&"
-A full version of the time and date, for example: Wed, 16 Oct 1995 09:51:40
-+0100. The timezone is always given as a numerical offset from UTC, with
-positive values used for timezones that are ahead (east) of UTC, and negative
-values for those that are behind (west).
-
-.vitem &$tod_log$&
-.vindex "&$tod_log$&"
-The time and date in the format used for writing Exim's log files, for example:
-1995-10-12 15:32:29, but without a timezone.
-
-.vitem &$tod_logfile$&
-.vindex "&$tod_logfile$&"
-This variable contains the date in the format yyyymmdd. This is the format that
-is used for datestamping log files when &%log_file_path%& contains the &`%D`&
-flag.
-
-.vitem &$tod_zone$&
-.vindex "&$tod_zone$&"
-This variable contains the numerical value of the local timezone, for example:
--0500.
-
-.vitem &$tod_zulu$&
-.vindex "&$tod_zulu$&"
-This variable contains the UTC date and time in &"Zulu"& format, as specified
-by ISO 8601, for example: 20030221154023Z.
-
-.vitem &$transport_name$&
-.cindex "transport" "name"
-.cindex "name" "of transport"
-.vindex "&$transport_name$&"
-During the running of a transport, this variable contains its name.
-
-.vitem &$value$&
-.vindex "&$value$&"
-This variable contains the result of an expansion lookup, extraction operation,
-or external command, as described above. It is also used during a
-&*reduce*& expansion.
-
-.vitem &$verify_mode$&
-.vindex "&$verify_mode$&"
-While a router or transport is being run in verify mode or for cutthrough delivery,
-contains "S" for sender-verification or "R" for recipient-verification.
-Otherwise, empty.
-
-.vitem &$version_number$&
-.vindex "&$version_number$&"
-The version number of Exim. Same as &$exim_version$&, may be overridden
-by the &%exim_version%& main config option.
-
-.vitem &$warn_message_delay$&
-.vindex "&$warn_message_delay$&"
-This variable is set only during the creation of a message warning about a
-delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
-
-.vitem &$warn_message_recipients$&
-.vindex "&$warn_message_recipients$&"
-This variable is set only during the creation of a message warning about a
-delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
-.endlist
-.ecindex IIDstrexp
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "Embedded Perl" "CHAPperl"
-.scindex IIDperl "Perl" "calling from Exim"
-Exim can be built to include an embedded Perl interpreter. When this is done,
-Perl subroutines can be called as part of the string expansion process. To make
-use of the Perl support, you need version 5.004 or later of Perl installed on
-your system. To include the embedded interpreter in the Exim binary, include
-the line
-.code
-EXIM_PERL = perl.o
-.endd
-in your &_Local/Makefile_& and then build Exim in the normal way.
-
-
-.section "Setting up so Perl can be used" "SECID85"
-.oindex "&%perl_startup%&"
-Access to Perl subroutines is via a global configuration option called
-&%perl_startup%& and an expansion string operator &%${perl ...}%&. If there is
-no &%perl_startup%& option in the Exim configuration file then no Perl
-interpreter is started and there is almost no overhead for Exim (since none of
-the Perl library will be paged in unless used). If there is a &%perl_startup%&
-option then the associated value is taken to be Perl code which is executed in
-a newly created Perl interpreter.
-
-The value of &%perl_startup%& is not expanded in the Exim sense, so you do not
-need backslashes before any characters to escape special meanings. The option
-should usually be something like
-.code
-perl_startup = do '/etc/exim.pl'
-.endd
-where &_/etc/exim.pl_& is Perl code which defines any subroutines you want to
-use from Exim. Exim can be configured either to start up a Perl interpreter as
-soon as it is entered, or to wait until the first time it is needed. Starting
-the interpreter at the beginning ensures that it is done while Exim still has
-its setuid privilege, but can impose an unnecessary overhead if Perl is not in
-fact used in a particular run. Also, note that this does not mean that Exim is
-necessarily running as root when Perl is called at a later time. By default,
-the interpreter is started only when it is needed, but this can be changed in
-two ways:
-
-.ilist
-.oindex "&%perl_at_start%&"
-Setting &%perl_at_start%& (a boolean option) in the configuration requests
-a startup when Exim is entered.
-.next
-The command line option &%-ps%& also requests a startup when Exim is entered,
-overriding the setting of &%perl_at_start%&.
-.endlist
-
-There is also a command line option &%-pd%& (for delay) which suppresses the
-initial startup, even if &%perl_at_start%& is set.
-
-.ilist
-.oindex "&%perl_taintmode%&"
-.cindex "Perl" "taintmode"
-To provide more security executing Perl code via the embedded Perl
-interpreter, the &%perl_taintmode%& option can be set. This enables the
-taint mode of the Perl interpreter. You are encouraged to set this
-option to a true value. To avoid breaking existing installations, it
-defaults to false.
-
-
-.section "Calling Perl subroutines" "SECID86"
-When the configuration file includes a &%perl_startup%& option you can make use
-of the string expansion item to call the Perl subroutines that are defined
-by the &%perl_startup%& code. The operator is used in any of the following
-forms:
-.code
-${perl{foo}}
-${perl{foo}{argument}}
-${perl{foo}{argument1}{argument2} ... }
-.endd
-which calls the subroutine &%foo%& with the given arguments. A maximum of eight
-arguments may be passed. Passing more than this results in an expansion failure
-with an error message of the form
-.code
-Too many arguments passed to Perl subroutine "foo" (max is 8)
-.endd
-The return value of the Perl subroutine is evaluated in a scalar context before
-it is passed back to Exim to be inserted into the expanded string. If the
-return value is &'undef'&, the expansion is forced to fail in the same way as
-an explicit &"fail"& on an &%if%& or &%lookup%& item. If the subroutine aborts
-by obeying Perl's &%die%& function, the expansion fails with the error message
-that was passed to &%die%&.
-
-
-.section "Calling Exim functions from Perl" "SECID87"
-Within any Perl code called from Exim, the function &'Exim::expand_string()'&
-is available to call back into Exim's string expansion function. For example,
-the Perl code
-.code
-my $lp = Exim::expand_string('$local_part');
-.endd
-makes the current Exim &$local_part$& available in the Perl variable &$lp$&.
-Note those are single quotes and not double quotes to protect against
-&$local_part$& being interpolated as a Perl variable.
-
-If the string expansion is forced to fail by a &"fail"& item, the result of
-&'Exim::expand_string()'& is &%undef%&. If there is a syntax error in the
-expansion string, the Perl call from the original expansion string fails with
-an appropriate error message, in the same way as if &%die%& were used.
-
-.cindex "debugging" "from embedded Perl"
-.cindex "log" "writing from embedded Perl"
-Two other Exim functions are available for use from within Perl code.
-&'Exim::debug_write()'& writes a string to the standard error stream if Exim's
-debugging is enabled. If you want a newline at the end, you must supply it.
-&'Exim::log_write()'& writes a string to Exim's main log, adding a leading
-timestamp. In this case, you should not supply a terminating newline.
-
-
-.section "Use of standard output and error by Perl" "SECID88"
-.cindex "Perl" "standard output and error"
-You should not write to the standard error or output streams from within your
-Perl code, as it is not defined how these are set up. In versions of Exim
-before 4.50, it is possible for the standard output or error to refer to the
-SMTP connection during message reception via the daemon. Writing to this stream
-is certain to cause chaos. From Exim 4.50 onwards, the standard output and
-error streams are connected to &_/dev/null_& in the daemon. The chaos is
-avoided, but the output is lost.
-
-.cindex "Perl" "use of &%warn%&"
-The Perl &%warn%& statement writes to the standard error stream by default.
-Calls to &%warn%& may be embedded in Perl modules that you use, but over which
-you have no control. When Exim starts up the Perl interpreter, it arranges for
-output from the &%warn%& statement to be written to the Exim main log. You can
-change this by including appropriate Perl magic somewhere in your Perl code.
-For example, to discard &%warn%& output completely, you need this:
-.code
-$SIG{__WARN__} = sub { };
-.endd
-Whenever a &%warn%& is obeyed, the anonymous subroutine is called. In this
-example, the code for the subroutine is empty, so it does nothing, but you can
-include any Perl code that you like. The text of the &%warn%& message is passed
-as the first subroutine argument.
-.ecindex IIDperl
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "Starting the daemon and the use of network interfaces" &&&
-         "CHAPinterfaces" &&&
-         "Starting the daemon"
-.cindex "daemon" "starting"
-.cindex "interface" "listening"
-.cindex "network interface"
-.cindex "interface" "network"
-.cindex "IP address" "for listening"
-.cindex "daemon" "listening IP addresses"
-.cindex "TCP/IP" "setting listening interfaces"
-.cindex "TCP/IP" "setting listening ports"
-A host that is connected to a TCP/IP network may have one or more physical
-hardware network interfaces. Each of these interfaces may be configured as one
-or more &"logical"& interfaces, which are the entities that a program actually
-works with. Each of these logical interfaces is associated with an IP address.
-In addition, TCP/IP software supports &"loopback"& interfaces (127.0.0.1 in
-IPv4 and ::1 in IPv6), which do not use any physical hardware. Exim requires
-knowledge about the host's interfaces for use in three different circumstances:
-
-.olist
-When a listening daemon is started, Exim needs to know which interfaces
-and ports to listen on.
-.next
-When Exim is routing an address, it needs to know which IP addresses
-are associated with local interfaces. This is required for the correct
-processing of MX lists by removing the local host and others with the
-same or higher priority values. Also, Exim needs to detect cases
-when an address is routed to an IP address that in fact belongs to the
-local host. Unless the &%self%& router option or the &%allow_localhost%&
-option of the smtp transport is set (as appropriate), this is treated
-as an error situation.
-.next
-When Exim connects to a remote host, it may need to know which interface to use
-for the outgoing connection.
-.endlist
-
-
-Exim's default behaviour is likely to be appropriate in the vast majority
-of cases. If your host has only one interface, and you want all its IP
-addresses to be treated in the same way, and you are using only the
-standard SMTP port, you should not need to take any special action. The
-rest of this chapter does not apply to you.
-
-In a more complicated situation you may want to listen only on certain
-interfaces, or on different ports, and for this reason there are a number of
-options that can be used to influence Exim's behaviour. The rest of this
-chapter describes how they operate.
-
-When a message is received over TCP/IP, the interface and port that were
-actually used are set in &$received_ip_address$& and &$received_port$&.
-
-
-
-.section "Starting a listening daemon" "SECID89"
-When a listening daemon is started (by means of the &%-bd%& command line
-option), the interfaces and ports on which it listens are controlled by the
-following options:
-
-.ilist
-&%daemon_smtp_ports%& contains a list of default ports
-or service names.
-(For backward compatibility, this option can also be specified in the singular.)
-.next
-&%local_interfaces%& contains list of interface IP addresses on which to
-listen. Each item may optionally also specify a port.
-.endlist
-
-The default list separator in both cases is a colon, but this can be changed as
-described in section &<<SECTlistsepchange>>&. When IPv6 addresses are involved,
-it is usually best to change the separator to avoid having to double all the
-colons. For example:
-.code
-local_interfaces = <; 127.0.0.1 ; \
-                      192.168.23.65 ; \
-                      ::1 ; \
-                      3ffe:ffff:836f::fe86:a061
-.endd
-There are two different formats for specifying a port along with an IP address
-in &%local_interfaces%&:
-
-.olist
-The port is added onto the address with a dot separator. For example, to listen
-on port 1234 on two different IP addresses:
-.code
-local_interfaces = <; 192.168.23.65.1234 ; \
-                      3ffe:ffff:836f::fe86:a061.1234
-.endd
-.next
-The IP address is enclosed in square brackets, and the port is added
-with a colon separator, for example:
-.code
-local_interfaces = <; [192.168.23.65]:1234 ; \
-                      [3ffe:ffff:836f::fe86:a061]:1234
-.endd
-.endlist
-
-When a port is not specified, the value of &%daemon_smtp_ports%& is used. The
-default setting contains just one port:
-.code
-daemon_smtp_ports = smtp
-.endd
-If more than one port is listed, each interface that does not have its own port
-specified listens on all of them. Ports that are listed in
-&%daemon_smtp_ports%& can be identified either by name (defined in
-&_/etc/services_&) or by number. However, when ports are given with individual
-IP addresses in &%local_interfaces%&, only numbers (not names) can be used.
-
-
-
-.section "Special IP listening addresses" "SECID90"
-The addresses 0.0.0.0 and ::0 are treated specially. They are interpreted
-as &"all IPv4 interfaces"& and &"all IPv6 interfaces"&, respectively. In each
-case, Exim tells the TCP/IP stack to &"listen on all IPv&'x'& interfaces"&
-instead of setting up separate listening sockets for each interface. The
-default value of &%local_interfaces%& is
-.code
-local_interfaces = 0.0.0.0
-.endd
-when Exim is built without IPv6 support; otherwise it is:
-.code
-local_interfaces = <; ::0 ; 0.0.0.0
-.endd
-Thus, by default, Exim listens on all available interfaces, on the SMTP port.
-
-
-
-.section "Overriding local_interfaces and daemon_smtp_ports" "SECID91"
-The &%-oX%& command line option can be used to override the values of
-&%daemon_smtp_ports%& and/or &%local_interfaces%& for a particular daemon
-instance. Another way of doing this would be to use macros and the &%-D%&
-option. However, &%-oX%& can be used by any admin user, whereas modification of
-the runtime configuration by &%-D%& is allowed only when the caller is root or
-exim.
-
-The value of &%-oX%& is a list of items. The default colon separator can be
-changed in the usual way (&<<SECTlistsepchange>>&) if required.
-If there are any items that do not
-contain dots or colons (that is, are not IP addresses), the value of
-&%daemon_smtp_ports%& is replaced by the list of those items. If there are any
-items that do contain dots or colons, the value of &%local_interfaces%& is
-replaced by those items. Thus, for example,
-.code
--oX 1225
-.endd
-overrides &%daemon_smtp_ports%&, but leaves &%local_interfaces%& unchanged,
-whereas
-.code
--oX 192.168.34.5.1125
-.endd
-overrides &%local_interfaces%&, leaving &%daemon_smtp_ports%& unchanged.
-(However, since &%local_interfaces%& now contains no items without ports, the
-value of &%daemon_smtp_ports%& is no longer relevant in this example.)
-
-
-
-.section "Support for the submissions (aka SSMTP or SMTPS) protocol" "SECTsupobssmt"
-.cindex "submissions protocol"
-.cindex "ssmtp protocol"
-.cindex "smtps protocol"
-.cindex "SMTP" "ssmtp protocol"
-.cindex "SMTP" "smtps protocol"
-Exim supports the use of TLS-on-connect, used by mail clients in the
-&"submissions"& protocol, historically also known as SMTPS or SSMTP.
-For some years, IETF Standards Track documents only blessed the
-STARTTLS-based Submission service (port 587) while common practice was to support
-the same feature set on port 465, but using TLS-on-connect.
-If your installation needs to provide service to mail clients
-(Mail User Agents, MUAs) then you should provide service on both the 587 and
-the 465 TCP ports.
-
-If the &%tls_on_connect_ports%& option is set to a list of port numbers or
-service names, connections to those ports must first establish TLS, before
-proceeding to the application layer use of the SMTP protocol.
-
-The common use of this option is expected to be
-.code
-tls_on_connect_ports = 465
-.endd
-per RFC 8314.
-There is also a command line option &%-tls-on-connect%&, which forces all ports
-to behave in this way when a daemon is started.
-
-&*Warning*&: Setting &%tls_on_connect_ports%& does not of itself cause the
-daemon to listen on those ports. You must still specify them in
-&%daemon_smtp_ports%&, &%local_interfaces%&, or the &%-oX%& option. (This is
-because &%tls_on_connect_ports%& applies to &%inetd%& connections as well as to
-connections via the daemon.)
-
-
-
-
-.section "IPv6 address scopes" "SECID92"
-.cindex "IPv6" "address scopes"
-IPv6 addresses have &"scopes"&, and a host with multiple hardware interfaces
-can, in principle, have the same link-local IPv6 address on different
-interfaces. Thus, additional information is needed, over and above the IP
-address, to distinguish individual interfaces. A convention of using a
-percent sign followed by something (often the interface name) has been
-adopted in some cases, leading to addresses like this:
-.code
-fe80::202:b3ff:fe03:45c1%eth0
-.endd
-To accommodate this usage, a percent sign followed by an arbitrary string is
-allowed at the end of an IPv6 address. By default, Exim calls &[getaddrinfo()]&
-to convert a textual IPv6 address for actual use. This function recognizes the
-percent convention in operating systems that support it, and it processes the
-address appropriately. Unfortunately, some older libraries have problems with
-&[getaddrinfo()]&. If
-.code
-IPV6_USE_INET_PTON=yes
-.endd
-is set in &_Local/Makefile_& (or an OS-dependent Makefile) when Exim is built,
-Exim uses &'inet_pton()'& to convert a textual IPv6 address for actual use,
-instead of &[getaddrinfo()]&. (Before version 4.14, it always used this
-function.) Of course, this means that the additional functionality of
-&[getaddrinfo()]& &-- recognizing scoped addresses &-- is lost.
-
-.section "Disabling IPv6" "SECID93"
-.cindex "IPv6" "disabling"
-Sometimes it happens that an Exim binary that was compiled with IPv6 support is
-run on a host whose kernel does not support IPv6. The binary will fall back to
-using IPv4, but it may waste resources looking up AAAA records, and trying to
-connect to IPv6 addresses, causing delays to mail delivery. If you set the
-.oindex "&%disable_ipv6%&"
-&%disable_ipv6%& option true, even if the Exim binary has IPv6 support, no IPv6
-activities take place. AAAA records are never looked up, and any IPv6 addresses
-that are listed in &%local_interfaces%&, data for the &(manualroute)& router,
-etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
-to handle IPv6 literal addresses.
-
-On the other hand, when IPv6 is in use, there may be times when you want to
-disable it for certain hosts or domains. You can use the &%dns_ipv4_lookup%&
-option to globally suppress the lookup of AAAA records for specified domains,
-and you can use the &%ignore_target_hosts%& generic router option to ignore
-IPv6 addresses in an individual router.
-
-
-
-.section "Examples of starting a listening daemon" "SECID94"
-The default case in an IPv6 environment is
-.code
-daemon_smtp_ports = smtp
-local_interfaces = <; ::0 ; 0.0.0.0
-.endd
-This specifies listening on the smtp port on all IPv6 and IPv4 interfaces.
-Either one or two sockets may be used, depending on the characteristics of
-the TCP/IP stack. (This is complicated and messy; for more information,
-read the comments in the &_daemon.c_& source file.)
-
-To specify listening on ports 25 and 26 on all interfaces:
-.code
-daemon_smtp_ports = 25 : 26
-.endd
-(leaving &%local_interfaces%& at the default setting) or, more explicitly:
-.code
-local_interfaces = <; ::0.25     ; ::0.26 \
-                      0.0.0.0.25 ; 0.0.0.0.26
-.endd
-To listen on the default port on all IPv4 interfaces, and on port 26 on the
-IPv4 loopback address only:
-.code
-local_interfaces = 0.0.0.0 : 127.0.0.1.26
-.endd
-To specify listening on the default port on specific interfaces only:
-.code
-local_interfaces = 10.0.0.67 : 192.168.34.67
-.endd
-&*Warning*&: Such a setting excludes listening on the loopback interfaces.
-
-
-
-.section "Recognizing the local host" "SECTreclocipadd"
-The &%local_interfaces%& option is also used when Exim needs to determine
-whether or not an IP address refers to the local host. That is, the IP
-addresses of all the interfaces on which a daemon is listening are always
-treated as local.
-
-For this usage, port numbers in &%local_interfaces%& are ignored. If either of
-the items 0.0.0.0 or ::0 are encountered, Exim gets a complete list of
-available interfaces from the operating system, and extracts the relevant
-(that is, IPv4 or IPv6) addresses to use for checking.
-
-Some systems set up large numbers of virtual interfaces in order to provide
-many virtual web servers. In this situation, you may want to listen for
-email on only a few of the available interfaces, but nevertheless treat all
-interfaces as local when routing. You can do this by setting
-&%extra_local_interfaces%& to a list of IP addresses, possibly including the
-&"all"& wildcard values. These addresses are recognized as local, but are not
-used for listening. Consider this example:
-.code
-local_interfaces = <; 127.0.0.1 ; ::1 ; \
-                      192.168.53.235 ; \
-                      3ffe:2101:12:1:a00:20ff:fe86:a061
-
-extra_local_interfaces = <; ::0 ; 0.0.0.0
-.endd
-The daemon listens on the loopback interfaces and just one IPv4 and one IPv6
-address, but all available interface addresses are treated as local when
-Exim is routing.
-
-In some environments the local host name may be in an MX list, but with an IP
-address that is not assigned to any local interface. In other cases it may be
-desirable to treat other host names as if they referred to the local host. Both
-these cases can be handled by setting the &%hosts_treat_as_local%& option.
-This contains host names rather than IP addresses. When a host is referenced
-during routing, either via an MX record or directly, it is treated as the local
-host if its name matches &%hosts_treat_as_local%&, or if any of its IP
-addresses match &%local_interfaces%& or &%extra_local_interfaces%&.
-
-
-
-.section "Delivering to a remote host" "SECID95"
-Delivery to a remote host is handled by the smtp transport. By default, it
-allows the system's TCP/IP functions to choose which interface to use (if
-there is more than one) when connecting to a remote host. However, the
-&%interface%& option can be set to specify which interface is used. See the
-description of the smtp transport in chapter &<<CHAPsmtptrans>>& for more
-details.
-
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "Main configuration" "CHAPmainconfig"
-.scindex IIDconfima "configuration file" "main section"
-.scindex IIDmaiconf "main configuration"
-The first part of the runtime configuration file contains three types of item:
-
-.ilist
-Macro definitions: These lines start with an upper case letter. See section
-&<<SECTmacrodefs>>& for details of macro processing.
-.next
-Named list definitions: These lines start with one of the words &"domainlist"&,
-&"hostlist"&, &"addresslist"&, or &"localpartlist"&. Their use is described in
-section &<<SECTnamedlists>>&.
-.next
-Main configuration settings: Each setting occupies one line of the file
-(with possible continuations). If any setting is preceded by the word
-&"hide"&, the &%-bP%& command line option displays its value to admin users
-only. See section &<<SECTcos>>& for a description of the syntax of these option
-settings.
-.endlist
-
-This chapter specifies all the main configuration options, along with their
-types and default values. For ease of finding a particular option, they appear
-in alphabetical order in section &<<SECTalomo>>& below. However, because there
-are now so many options, they are first listed briefly in functional groups, as
-an aid to finding the name of the option you are looking for. Some options are
-listed in more than one group.
-
-.section "Miscellaneous" "SECID96"
-.table2
-.row &%bi_command%&                  "to run for &%-bi%& command line option"
-.row &%debug_store%&                 "do extra internal checks"
-.row &%disable_ipv6%&                "do no IPv6 processing"
-.row &%keep_malformed%&              "for broken files &-- should not happen"
-.row &%localhost_number%&            "for unique message ids in clusters"
-.row &%message_body_newlines%&       "retain newlines in &$message_body$&"
-.row &%message_body_visible%&        "how much to show in &$message_body$&"
-.row &%mua_wrapper%&                 "run in &""MUA wrapper""& mode"
-.row &%print_topbitchars%&           "top-bit characters are printing"
-.row &%spool_wireformat%&            "use wire-format spool data files when possible"
-.row &%timezone%&                    "force time zone"
-.endtable
-
-
-.section "Exim parameters" "SECID97"
-.table2
-.row &%exim_group%&                  "override compiled-in value"
-.row &%exim_path%&                   "override compiled-in value"
-.row &%exim_user%&                   "override compiled-in value"
-.row &%primary_hostname%&            "default from &[uname()]&"
-.row &%split_spool_directory%&       "use multiple directories"
-.row &%spool_directory%&             "override compiled-in value"
-.endtable
-
-
-
-.section "Privilege controls" "SECID98"
-.table2
-.row &%admin_groups%&                "groups that are Exim admin users"
-.row &%commandline_checks_require_admin%& "require admin for various checks"
-.row &%deliver_drop_privilege%&      "drop root for delivery processes"
-.row &%local_from_check%&            "insert &'Sender:'& if necessary"
-.row &%local_from_prefix%&           "for testing &'From:'& for local sender"
-.row &%local_from_suffix%&           "for testing &'From:'& for local sender"
-.row &%local_sender_retain%&         "keep &'Sender:'& from untrusted user"
-.row &%never_users%&                 "do not run deliveries as these"
-.row &%prod_requires_admin%&         "forced delivery requires admin user"
-.row &%queue_list_requires_admin%&   "queue listing requires admin user"
-.row &%trusted_groups%&              "groups that are trusted"
-.row &%trusted_users%&               "users that are trusted"
-.endtable
-
-
-
-.section "Logging" "SECID99"
-.table2
-.row &%event_action%&                "custom logging"
-.row &%hosts_connection_nolog%&      "exemption from connect logging"
-.row &%log_file_path%&               "override compiled-in value"
-.row &%log_selector%&                "set/unset optional logging"
-.row &%log_timezone%&                "add timezone to log lines"
-.row &%message_logs%&                "create per-message logs"
-.row &%preserve_message_logs%&       "after message completion"
-.row &%process_log_path%&            "for SIGUSR1 and &'exiwhat'&"
-.row &%slow_lookup_log%&             "control logging of slow DNS lookups"
-.row &%syslog_duplication%&          "controls duplicate log lines on syslog"
-.row &%syslog_facility%&             "set syslog &""facility""& field"
-.row &%syslog_pid%&                  "pid in syslog lines"
-.row &%syslog_processname%&          "set syslog &""ident""& field"
-.row &%syslog_timestamp%&            "timestamp syslog lines"
-.row &%write_rejectlog%&             "control use of message log"
-.endtable
-
-
-
-.section "Frozen messages" "SECID100"
-.table2
-.row &%auto_thaw%&                   "sets time for retrying frozen messages"
-.row &%freeze_tell%&                 "send message when freezing"
-.row &%move_frozen_messages%&        "to another directory"
-.row &%timeout_frozen_after%&        "keep frozen messages only so long"
-.endtable
-
-
-
-.section "Data lookups" "SECID101"
-.table2
-.row &%ibase_servers%&               "InterBase servers"
-.row &%ldap_ca_cert_dir%&            "dir of CA certs to verify LDAP server's"
-.row &%ldap_ca_cert_file%&           "file of CA certs to verify LDAP server's"
-.row &%ldap_cert_file%&              "client cert file for LDAP"
-.row &%ldap_cert_key%&               "client key file for LDAP"
-.row &%ldap_cipher_suite%&           "TLS negotiation preference control"
-.row &%ldap_default_servers%&        "used if no server in query"
-.row &%ldap_require_cert%&           "action to take without LDAP server cert"
-.row &%ldap_start_tls%&              "require TLS within LDAP"
-.row &%ldap_version%&                "set protocol version"
-.row &%lookup_open_max%&             "lookup files held open"
-.row &%mysql_servers%&               "default MySQL servers"
-.row &%oracle_servers%&              "Oracle servers"
-.row &%pgsql_servers%&               "default PostgreSQL servers"
-.row &%sqlite_lock_timeout%&         "as it says"
-.endtable
-
-
-
-.section "Message ids" "SECID102"
-.table2
-.row &%message_id_header_domain%&    "used to build &'Message-ID:'& header"
-.row &%message_id_header_text%&      "ditto"
-.endtable
-
-
-
-.section "Embedded Perl Startup" "SECID103"
-.table2
-.row &%perl_at_start%&               "always start the interpreter"
-.row &%perl_startup%&                "code to obey when starting Perl"
-.row &%perl_taintmode%&		     "enable taint mode in Perl"
-.endtable
-
-
-
-.section "Daemon" "SECID104"
-.table2
-.row &%daemon_smtp_ports%&           "default ports"
-.row &%daemon_startup_retries%&      "number of times to retry"
-.row &%daemon_startup_sleep%&        "time to sleep between tries"
-.row &%extra_local_interfaces%&      "not necessarily listened on"
-.row &%local_interfaces%&            "on which to listen, with optional ports"
-.row &%notifier_socket%&             "override compiled-in value"
-.row &%pid_file_path%&               "override compiled-in value"
-.row &%queue_run_max%&               "maximum simultaneous queue runners"
-.endtable
-
-
-
-.section "Resource control" "SECID105"
-.table2
-.row &%check_log_inodes%&            "before accepting a message"
-.row &%check_log_space%&             "before accepting a message"
-.row &%check_spool_inodes%&          "before accepting a message"
-.row &%check_spool_space%&           "before accepting a message"
-.row &%deliver_queue_load_max%&      "no queue deliveries if load high"
-.row &%queue_only_load%&             "queue incoming if load high"
-.row &%queue_only_load_latch%&       "don't re-evaluate load for each message"
-.row &%queue_run_max%&               "maximum simultaneous queue runners"
-.row &%remote_max_parallel%&         "parallel SMTP delivery per message"
-.row &%smtp_accept_max%&             "simultaneous incoming connections"
-.row &%smtp_accept_max_nonmail%&     "non-mail commands"
-.row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
-.row &%smtp_accept_max_per_connection%& "messages per connection"
-.row &%smtp_accept_max_per_host%&    "connections from one host"
-.row &%smtp_accept_queue%&           "queue mail if more connections"
-.row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
-                                           connection"
-.row &%smtp_accept_reserve%&         "only reserve hosts if more connections"
-.row &%smtp_check_spool_space%&      "from SIZE on MAIL command"
-.row &%smtp_connect_backlog%&        "passed to TCP/IP stack"
-.row &%smtp_load_reserve%&           "SMTP from reserved hosts if load high"
-.row &%smtp_reserve_hosts%&          "these are the reserve hosts"
-.endtable
-
-
-
-.section "Policy controls" "SECID106"
-.table2
-.row &%acl_not_smtp%&                "ACL for non-SMTP messages"
-.row &%acl_not_smtp_mime%&           "ACL for non-SMTP MIME parts"
-.row &%acl_not_smtp_start%&          "ACL for start of non-SMTP message"
-.row &%acl_smtp_auth%&               "ACL for AUTH"
-.row &%acl_smtp_connect%&            "ACL for connection"
-.row &%acl_smtp_data%&               "ACL for DATA"
-.row &%acl_smtp_data_prdr%&          "ACL for DATA, per-recipient"
-.row &%acl_smtp_dkim%&               "ACL for DKIM verification"
-.row &%acl_smtp_etrn%&               "ACL for ETRN"
-.row &%acl_smtp_expn%&               "ACL for EXPN"
-.row &%acl_smtp_helo%&               "ACL for EHLO or HELO"
-.row &%acl_smtp_mail%&               "ACL for MAIL"
-.row &%acl_smtp_mailauth%&           "ACL for AUTH on MAIL command"
-.row &%acl_smtp_mime%&               "ACL for MIME parts"
-.row &%acl_smtp_notquit%&            "ACL for non-QUIT terminations"
-.row &%acl_smtp_predata%&            "ACL for start of data"
-.row &%acl_smtp_quit%&               "ACL for QUIT"
-.row &%acl_smtp_rcpt%&               "ACL for RCPT"
-.row &%acl_smtp_starttls%&           "ACL for STARTTLS"
-.row &%acl_smtp_vrfy%&               "ACL for VRFY"
-.row &%av_scanner%&                  "specify virus scanner"
-.row &%check_rfc2047_length%&        "check length of RFC 2047 &""encoded &&&
-                                      words""&"
-.row &%dns_cname_loops%&             "follow CNAMEs returned by resolver"
-.row &%dns_csa_search_limit%&        "control CSA parent search depth"
-.row &%dns_csa_use_reverse%&         "en/disable CSA IP reverse search"
-.row &%header_maxsize%&              "total size of message header"
-.row &%header_line_maxsize%&         "individual header line limit"
-.row &%helo_accept_junk_hosts%&      "allow syntactic junk from these hosts"
-.row &%helo_allow_chars%&            "allow illegal chars in HELO names"
-.row &%helo_lookup_domains%&         "lookup hostname for these HELO names"
-.row &%helo_try_verify_hosts%&       "HELO soft-checked for these hosts"
-.row &%helo_verify_hosts%&           "HELO hard-checked for these hosts"
-.row &%host_lookup%&                 "host name looked up for these hosts"
-.row &%host_lookup_order%&           "order of DNS and local name lookups"
-.row &%hosts_proxy%&                 "use proxy protocol for these hosts"
-.row &%host_reject_connection%&      "reject connection from these hosts"
-.row &%hosts_treat_as_local%&        "useful in some cluster configurations"
-.row &%local_scan_timeout%&          "timeout for &[local_scan()]&"
-.row &%message_size_limit%&          "for all messages"
-.row &%percent_hack_domains%&        "recognize %-hack for these domains"
-.row &%spamd_address%&               "set interface to SpamAssassin"
-.row &%strict_acl_vars%&             "object to unset ACL variables"
-.endtable
-
-
-
-.section "Callout cache" "SECID107"
-.table2
-.row &%callout_domain_negative_expire%& "timeout for negative domain cache &&&
-                                         item"
-.row &%callout_domain_positive_expire%& "timeout for positive domain cache &&&
-                                         item"
-.row &%callout_negative_expire%&     "timeout for negative address cache item"
-.row &%callout_positive_expire%&     "timeout for positive address cache item"
-.row &%callout_random_local_part%&   "string to use for &""random""& testing"
-.endtable
-
-
-
-.section "TLS" "SECID108"
-.table2
-.row &%gnutls_compat_mode%&          "use GnuTLS compatibility mode"
-.row &%gnutls_allow_auto_pkcs11%&    "allow GnuTLS to autoload PKCS11 modules"
-.row &%openssl_options%&             "adjust OpenSSL compatibility options"
-.row &%tls_advertise_hosts%&         "advertise TLS to these hosts"
-.row &%tls_certificate%&             "location of server certificate"
-.row &%tls_crl%&                     "certificate revocation list"
-.row &%tls_dh_max_bits%&             "clamp D-H bit count suggestion"
-.row &%tls_dhparam%&                 "DH parameters for server"
-.row &%tls_eccurve%&                 "EC curve selection for server"
-.row &%tls_ocsp_file%&               "location of server certificate status proof"
-.row &%tls_on_connect_ports%&        "specify SSMTP (SMTPS) ports"
-.row &%tls_privatekey%&              "location of server private key"
-.row &%tls_remember_esmtp%&          "don't reset after starting TLS"
-.row &%tls_require_ciphers%&         "specify acceptable ciphers"
-.row &%tls_try_verify_hosts%&        "try to verify client certificate"
-.row &%tls_verify_certificates%&     "expected client certificates"
-.row &%tls_verify_hosts%&            "insist on client certificate verify"
-.endtable
-
-
-
-.section "Local user handling" "SECID109"
-.table2
-.row &%finduser_retries%&            "useful in NIS environments"
-.row &%gecos_name%&                  "used when creating &'Sender:'&"
-.row &%gecos_pattern%&               "ditto"
-.row &%max_username_length%&         "for systems that truncate"
-.row &%unknown_login%&               "used when no login name found"
-.row &%unknown_username%&            "ditto"
-.row &%uucp_from_pattern%&           "for recognizing &""From ""& lines"
-.row &%uucp_from_sender%&            "ditto"
-.endtable
-
-
-
-.section "All incoming messages (SMTP and non-SMTP)" "SECID110"
-.table2
-.row &%header_maxsize%&              "total size of message header"
-.row &%header_line_maxsize%&         "individual header line limit"
-.row &%message_size_limit%&          "applies to all messages"
-.row &%percent_hack_domains%&        "recognize %-hack for these domains"
-.row &%received_header_text%&        "expanded to make &'Received:'&"
-.row &%received_headers_max%&        "for mail loop detection"
-.row &%recipients_max%&              "limit per message"
-.row &%recipients_max_reject%&       "permanently reject excess recipients"
-.endtable
-
-
-
-
-.section "Non-SMTP incoming messages" "SECID111"
-.table2
-.row &%receive_timeout%&             "for non-SMTP messages"
-.endtable
-
-
-
-
-
-.section "Incoming SMTP messages" "SECID112"
-See also the &'Policy controls'& section above.
-
-.table2
-.row &%dkim_verify_hashes%&          "DKIM hash methods accepted for signatures"
-.row &%dkim_verify_keytypes%&        "DKIM key types accepted for signatures"
-.row &%dkim_verify_signers%&         "DKIM domains for which DKIM ACL is run"
-.row &%host_lookup%&                 "host name looked up for these hosts"
-.row &%host_lookup_order%&           "order of DNS and local name lookups"
-.row &%recipient_unqualified_hosts%& "may send unqualified recipients"
-.row &%rfc1413_hosts%&               "make ident calls to these hosts"
-.row &%rfc1413_query_timeout%&       "zero disables ident calls"
-.row &%sender_unqualified_hosts%&    "may send unqualified senders"
-.row &%smtp_accept_keepalive%&       "some TCP/IP magic"
-.row &%smtp_accept_max%&             "simultaneous incoming connections"
-.row &%smtp_accept_max_nonmail%&     "non-mail commands"
-.row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
-.row &%smtp_accept_max_per_connection%& "messages per connection"
-.row &%smtp_accept_max_per_host%&    "connections from one host"
-.row &%smtp_accept_queue%&           "queue mail if more connections"
-.row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
-                                           connection"
-.row &%smtp_accept_reserve%&         "only reserve hosts if more connections"
-.row &%smtp_active_hostname%&        "host name to use in messages"
-.row &%smtp_banner%&                 "text for welcome banner"
-.row &%smtp_check_spool_space%&      "from SIZE on MAIL command"
-.row &%smtp_connect_backlog%&        "passed to TCP/IP stack"
-.row &%smtp_enforce_sync%&           "of SMTP command/responses"
-.row &%smtp_etrn_command%&           "what to run for ETRN"
-.row &%smtp_etrn_serialize%&         "only one at once"
-.row &%smtp_load_reserve%&           "only reserve hosts if this load"
-.row &%smtp_max_unknown_commands%&   "before dropping connection"
-.row &%smtp_ratelimit_hosts%&        "apply ratelimiting to these hosts"
-.row &%smtp_ratelimit_mail%&         "ratelimit for MAIL commands"
-.row &%smtp_ratelimit_rcpt%&         "ratelimit for RCPT commands"
-.row &%smtp_receive_timeout%&        "per command or data line"
-.row &%smtp_reserve_hosts%&          "these are the reserve hosts"
-.row &%smtp_return_error_details%&   "give detail on rejections"
-.endtable
-
-
-
-.section "SMTP extensions" "SECID113"
-.table2
-.row &%accept_8bitmime%&             "advertise 8BITMIME"
-.row &%auth_advertise_hosts%&        "advertise AUTH to these hosts"
-.row &%chunking_advertise_hosts%&    "advertise CHUNKING to these hosts"
-.row &%dsn_advertise_hosts%&         "advertise DSN extensions to these hosts"
-.row &%ignore_fromline_hosts%&       "allow &""From ""& from these hosts"
-.row &%ignore_fromline_local%&       "allow &""From ""& from local SMTP"
-.row &%pipelining_advertise_hosts%&  "advertise pipelining to these hosts"
-.row &%pipelining_connect_advertise_hosts%& "advertise pipelining to these hosts"
-.row &%prdr_enable%&                 "advertise PRDR to all hosts"
-.row &%smtputf8_advertise_hosts%&    "advertise SMTPUTF8 to these hosts"
-.row &%tls_advertise_hosts%&         "advertise TLS to these hosts"
-.endtable
-
-
-
-.section "Processing messages" "SECID114"
-.table2
-.row &%allow_domain_literals%&       "recognize domain literal syntax"
-.row &%allow_mx_to_ip%&              "allow MX to point to IP address"
-.row &%allow_utf8_domains%&          "in addresses"
-.row &%check_rfc2047_length%&        "check length of RFC 2047 &""encoded &&&
-                                      words""&"
-.row &%delivery_date_remove%&        "from incoming messages"
-.row &%envelope_to_remove%&          "from incoming messages"
-.row &%extract_addresses_remove_arguments%& "affects &%-t%& processing"
-.row &%headers_charset%&             "default for translations"
-.row &%qualify_domain%&              "default for senders"
-.row &%qualify_recipient%&           "default for recipients"
-.row &%return_path_remove%&          "from incoming messages"
-.row &%strip_excess_angle_brackets%& "in addresses"
-.row &%strip_trailing_dot%&          "at end of addresses"
-.row &%untrusted_set_sender%&        "untrusted can set envelope sender"
-.endtable
-
-
-
-.section "System filter" "SECID115"
-.table2
-.row &%system_filter%&               "locate system filter"
-.row &%system_filter_directory_transport%& "transport for delivery to a &&&
-                                            directory"
-.row &%system_filter_file_transport%& "transport for delivery to a file"
-.row &%system_filter_group%&         "group for filter running"
-.row &%system_filter_pipe_transport%& "transport for delivery to a pipe"
-.row &%system_filter_reply_transport%& "transport for autoreply delivery"
-.row &%system_filter_user%&          "user for filter running"
-.endtable
-
-
-
-.section "Routing and delivery" "SECID116"
-.table2
-.row &%disable_ipv6%&                "do no IPv6 processing"
-.row &%dns_again_means_nonexist%&    "for broken domains"
-.row &%dns_check_names_pattern%&     "pre-DNS syntax check"
-.row &%dns_dnssec_ok%&               "parameter for resolver"
-.row &%dns_ipv4_lookup%&             "only v4 lookup for these domains"
-.row &%dns_retrans%&                 "parameter for resolver"
-.row &%dns_retry%&                   "parameter for resolver"
-.row &%dns_trust_aa%&                "DNS zones trusted as authentic"
-.row &%dns_use_edns0%&               "parameter for resolver"
-.row &%hold_domains%&                "hold delivery for these domains"
-.row &%local_interfaces%&            "for routing checks"
-.row &%queue_domains%&               "no immediate delivery for these"
-.row &%queue_only%&                  "no immediate delivery at all"
-.row &%queue_only_file%&             "no immediate delivery if file exists"
-.row &%queue_only_load%&             "no immediate delivery if load is high"
-.row &%queue_only_load_latch%&       "don't re-evaluate load for each message"
-.row &%queue_only_override%&         "allow command line to override"
-.row &%queue_run_in_order%&          "order of arrival"
-.row &%queue_run_max%&               "of simultaneous queue runners"
-.row &%queue_smtp_domains%&          "no immediate SMTP delivery for these"
-.row &%remote_max_parallel%&         "parallel SMTP delivery per message"
-.row &%remote_sort_domains%&         "order of remote deliveries"
-.row &%retry_data_expire%&           "timeout for retry data"
-.row &%retry_interval_max%&          "safety net for retry rules"
-.endtable
-
-
-
-.section "Bounce and warning messages" "SECID117"
-.table2
-.row &%bounce_message_file%&         "content of bounce"
-.row &%bounce_message_text%&         "content of bounce"
-.row &%bounce_return_body%&          "include body if returning message"
-.row &%bounce_return_linesize_limit%& "limit on returned message line length"
-.row &%bounce_return_message%&       "include original message in bounce"
-.row &%bounce_return_size_limit%&    "limit on returned message"
-.row &%bounce_sender_authentication%& "send authenticated sender with bounce"
-.row &%dsn_from%&                    "set &'From:'& contents in bounces"
-.row &%errors_copy%&                 "copy bounce messages"
-.row &%errors_reply_to%&             "&'Reply-to:'& in bounces"
-.row &%delay_warning%&               "time schedule"
-.row &%delay_warning_condition%&     "condition for warning messages"
-.row &%ignore_bounce_errors_after%&  "discard undeliverable bounces"
-.row &%smtp_return_error_details%&   "give detail on rejections"
-.row &%warn_message_file%&           "content of warning message"
-.endtable
-
-
-
-.section "Alphabetical list of main options" "SECTalomo"
-Those options that undergo string expansion before use are marked with
-&dagger;.
-
-.option accept_8bitmime main boolean true
-.cindex "8BITMIME"
-.cindex "8-bit characters"
-.cindex "log" "selectors"
-.cindex "log" "8BITMIME"
-This option causes Exim to send 8BITMIME in its response to an SMTP
-EHLO command, and to accept the BODY= parameter on MAIL commands.
-However, though Exim is 8-bit clean, it is not a protocol converter, and it
-takes no steps to do anything special with messages received by this route.
-
-Historically Exim kept this option off by default, but the maintainers
-feel that in today's Internet, this causes more problems than it solves.
-It now defaults to true.
-A more detailed analysis of the issues is provided by Dan Bernstein:
-.display
-&url(https://cr.yp.to/smtp/8bitmime.html)
-.endd
-
-To log received 8BITMIME status use
-.code
-log_selector = +8bitmime
-.endd
-
-.option acl_not_smtp main string&!! unset
-.cindex "&ACL;" "for non-SMTP messages"
-.cindex "non-SMTP messages" "ACLs for"
-This option defines the ACL that is run when a non-SMTP message has been
-read and is on the point of being accepted. See chapter &<<CHAPACL>>& for
-further details.
-
-.option acl_not_smtp_mime main string&!! unset
-This option defines the ACL that is run for individual MIME parts of non-SMTP
-messages. It operates in exactly the same way as &%acl_smtp_mime%& operates for
-SMTP messages.
-
-.option acl_not_smtp_start main string&!! unset
-.cindex "&ACL;" "at start of non-SMTP message"
-.cindex "non-SMTP messages" "ACLs for"
-This option defines the ACL that is run before Exim starts reading a
-non-SMTP message. See chapter &<<CHAPACL>>& for further details.
-
-.option acl_smtp_auth main string&!! unset
-.cindex "&ACL;" "setting up for SMTP commands"
-.cindex "AUTH" "ACL for"
-This option defines the ACL that is run when an SMTP AUTH command is
-received. See chapter &<<CHAPACL>>& for further details.
-
-.option acl_smtp_connect main string&!! unset
-.cindex "&ACL;" "on SMTP connection"
-This option defines the ACL that is run when an SMTP connection is received.
-See chapter &<<CHAPACL>>& for further details.
-
-.option acl_smtp_data main string&!! unset
-.cindex "DATA" "ACL for"
-This option defines the ACL that is run after an SMTP DATA command has been
-processed and the message itself has been received, but before the final
-acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
-
-.option acl_smtp_data_prdr main string&!! accept
-.cindex "PRDR" "ACL for"
-.cindex "DATA" "PRDR ACL for"
-.cindex "&ACL;" "PRDR-related"
-.cindex "&ACL;" "per-user data processing"
-This option defines the ACL that,
-if the PRDR feature has been negotiated,
-is run for each recipient after an SMTP DATA command has been
-processed and the message itself has been received, but before the
-acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
-
-.option acl_smtp_dkim main string&!! unset
-.cindex DKIM "ACL for"
-This option defines the ACL that is run for each DKIM signature
-(by default, or as specified in the dkim_verify_signers option)
-of a received message.
-See section &<<SECDKIMVFY>>& for further details.
-
-.option acl_smtp_etrn main string&!! unset
-.cindex "ETRN" "ACL for"
-This option defines the ACL that is run when an SMTP ETRN command is
-received. See chapter &<<CHAPACL>>& for further details.
-
-.option acl_smtp_expn main string&!! unset
-.cindex "EXPN" "ACL for"
-This option defines the ACL that is run when an SMTP EXPN command is
-received. See chapter &<<CHAPACL>>& for further details.
-
-.option acl_smtp_helo main string&!! unset
-.cindex "EHLO" "ACL for"
-.cindex "HELO" "ACL for"
-This option defines the ACL that is run when an SMTP EHLO or HELO
-command is received. See chapter &<<CHAPACL>>& for further details.
-
-
-.option acl_smtp_mail main string&!! unset
-.cindex "MAIL" "ACL for"
-This option defines the ACL that is run when an SMTP MAIL command is
-received. See chapter &<<CHAPACL>>& for further details.
-
-.option acl_smtp_mailauth main string&!! unset
-.cindex "AUTH" "on MAIL command"
-This option defines the ACL that is run when there is an AUTH parameter on
-a MAIL command. See chapter &<<CHAPACL>>& for details of ACLs, and chapter
-&<<CHAPSMTPAUTH>>& for details of authentication.
-
-.option acl_smtp_mime main string&!! unset
-.cindex "MIME content scanning" "ACL for"
-This option is available when Exim is built with the content-scanning
-extension. It defines the ACL that is run for each MIME part in a message. See
-section &<<SECTscanmimepart>>& for details.
-
-.option acl_smtp_notquit main string&!! unset
-.cindex "not-QUIT, ACL for"
-This option defines the ACL that is run when an SMTP session
-ends without a QUIT command being received.
-See chapter &<<CHAPACL>>& for further details.
-
-.option acl_smtp_predata main string&!! unset
-This option defines the ACL that is run when an SMTP DATA command is
-received, before the message itself is received. See chapter &<<CHAPACL>>& for
-further details.
-
-.option acl_smtp_quit main string&!! unset
-.cindex "QUIT, ACL for"
-This option defines the ACL that is run when an SMTP QUIT command is
-received. See chapter &<<CHAPACL>>& for further details.
-
-.option acl_smtp_rcpt main string&!! unset
-.cindex "RCPT" "ACL for"
-This option defines the ACL that is run when an SMTP RCPT command is
-received. See chapter &<<CHAPACL>>& for further details.
-
-.option acl_smtp_starttls main string&!! unset
-.cindex "STARTTLS, ACL for"
-This option defines the ACL that is run when an SMTP STARTTLS command is
-received. See chapter &<<CHAPACL>>& for further details.
-
-.option acl_smtp_vrfy main string&!! unset
-.cindex "VRFY" "ACL for"
-This option defines the ACL that is run when an SMTP VRFY command is
-received. See chapter &<<CHAPACL>>& for further details.
-
-.option add_environment main "string list" empty
-.cindex "environment" "set values"
-This option adds individual environment variables that the
-currently linked libraries and programs in child processes may use.
-Each list element should be of the form &"name=value"&.
-
-See &<<SECTpipeenv>>& for the environment of &(pipe)& transports.
-
-.option admin_groups main "string list&!!" unset
-.cindex "admin user"
-This option is expanded just once, at the start of Exim's processing. If the
-current group or any of the supplementary groups of an Exim caller is in this
-colon-separated list, the caller has admin privileges. If all your system
-programmers are in a specific group, for example, you can give them all Exim
-admin privileges by putting that group in &%admin_groups%&. However, this does
-not permit them to read Exim's spool files (whose group owner is the Exim gid).
-To permit this, you have to add individuals to the Exim group.
-
-.option allow_domain_literals main boolean false
-.cindex "domain literal"
-If this option is set, the RFC 2822 domain literal format is permitted in
-email addresses. The option is not set by default, because the domain literal
-format is not normally required these days, and few people know about it. It
-has, however, been exploited by mail abusers.
-
-Unfortunately, it seems that some DNS black list maintainers are using this
-format to report black listing to postmasters. If you want to accept messages
-addressed to your hosts by IP address, you need to set
-&%allow_domain_literals%& true, and also to add &`@[]`& to the list of local
-domains (defined in the named domain list &%local_domains%& in the default
-configuration). This &"magic string"& matches the domain literal form of all
-the local host's IP addresses.
-
-
-.option allow_mx_to_ip main boolean false
-.cindex "MX record" "pointing to IP address"
-It appears that more and more DNS zone administrators are breaking the rules
-and putting domain names that look like IP addresses on the right hand side of
-MX records. Exim follows the rules and rejects this, giving an error message
-that explains the misconfiguration. However, some other MTAs support this
-practice, so to avoid &"Why can't Exim do this?"& complaints,
-&%allow_mx_to_ip%& exists, in order to enable this heinous activity. It is not
-recommended, except when you have no other choice.
-
-.option allow_utf8_domains main boolean false
-.cindex "domain" "UTF-8 characters in"
-.cindex "UTF-8" "in domain name"
-Lots of discussion is going on about internationalized domain names. One
-camp is strongly in favour of just using UTF-8 characters, and it seems
-that at least two other MTAs permit this.
-This option allows Exim users to experiment if they wish.
-
-If it is set true, Exim's domain parsing function allows valid
-UTF-8 multicharacters to appear in domain name components, in addition to
-letters, digits, and hyphens.
-
-If Exim is built with internationalization support
-and the SMTPUTF8 ESMTP option is in use (see chapter &<<CHAPi18n>>&)
-this option can be left as default.
-Without that,
-if you want to look up such domain names in the DNS, you must also
-adjust the value of &%dns_check_names_pattern%& to match the extended form. A
-suitable setting is:
-.code
-dns_check_names_pattern = (?i)^(?>(?(1)\.|())[a-z0-9\xc0-\xff]\
-  (?>[-a-z0-9\x80-\xff]*[a-z0-9\x80-\xbf])?)+$
-.endd
-Alternatively, you can just disable this feature by setting
-.code
-dns_check_names_pattern =
-.endd
-That is, set the option to an empty string so that no check is done.
-
-
-.option auth_advertise_hosts main "host list&!!" *
-.cindex "authentication" "advertising"
-.cindex "AUTH" "advertising"
-If any server authentication mechanisms are configured, Exim advertises them in
-response to an EHLO command only if the calling host matches this list.
-Otherwise, Exim does not advertise AUTH.
-Exim does not accept AUTH commands from clients to which it has not
-advertised the availability of AUTH. The advertising of individual
-authentication mechanisms can be controlled by the use of the
-&%server_advertise_condition%& generic authenticator option on the individual
-authenticators. See chapter &<<CHAPSMTPAUTH>>& for further details.
-
-Certain mail clients (for example, Netscape) require the user to provide a name
-and password for authentication if AUTH is advertised, even though it may
-not be needed (the host may accept messages from hosts on its local LAN without
-authentication, for example). The &%auth_advertise_hosts%& option can be used
-to make these clients more friendly by excluding them from the set of hosts to
-which Exim advertises AUTH.
-
-.cindex "AUTH" "advertising when encrypted"
-If you want to advertise the availability of AUTH only when the connection
-is encrypted using TLS, you can make use of the fact that the value of this
-option is expanded, with a setting like this:
-.code
-auth_advertise_hosts = ${if eq{$tls_in_cipher}{}{}{*}}
-.endd
-.vindex "&$tls_in_cipher$&"
-If &$tls_in_cipher$& is empty, the session is not encrypted, and the result of
-the expansion is empty, thus matching no hosts. Otherwise, the result of the
-expansion is *, which matches all hosts.
-
-
-.option auto_thaw main time 0s
-.cindex "thawing messages"
-.cindex "unfreezing messages"
-If this option is set to a time greater than zero, a queue runner will try a
-new delivery attempt on any frozen message, other than a bounce message, if
-this much time has passed since it was frozen. This may result in the message
-being re-frozen if nothing has changed since the last attempt. It is a way of
-saying &"keep on trying, even though there are big problems"&.
-
-&*Note*&: This is an old option, which predates &%timeout_frozen_after%& and
-&%ignore_bounce_errors_after%&. It is retained for compatibility, but it is not
-thought to be very useful any more, and its use should probably be avoided.
-
-
-.option av_scanner main string "see below"
-This option is available if Exim is built with the content-scanning extension.
-It specifies which anti-virus scanner to use. The default value is:
-.code
-sophie:/var/run/sophie
-.endd
-If the value of &%av_scanner%& starts with a dollar character, it is expanded
-before use. See section &<<SECTscanvirus>>& for further details.
-
-
-.option bi_command main string unset
-.oindex "&%-bi%&"
-This option supplies the name of a command that is run when Exim is called with
-the &%-bi%& option (see chapter &<<CHAPcommandline>>&). The string value is
-just the command name, it is not a complete command line. If an argument is
-required, it must come from the &%-oA%& command line option.
-
-
-.option bounce_message_file main string unset
-.cindex "bounce message" "customizing"
-.cindex "customizing" "bounce message"
-This option defines a template file containing paragraphs of text to be used
-for constructing bounce messages.  Details of the file's contents are given in
-chapter &<<CHAPemsgcust>>&. See also &%warn_message_file%&.
-
-
-.option bounce_message_text main string unset
-When this option is set, its contents are included in the default bounce
-message immediately after &"This message was created automatically by mail
-delivery software."& It is not used if &%bounce_message_file%& is set.
-
-.option bounce_return_body main boolean true
-.cindex "bounce message" "including body"
-This option controls whether the body of an incoming message is included in a
-bounce message when &%bounce_return_message%& is true. The default setting
-causes the entire message, both header and body, to be returned (subject to the
-value of &%bounce_return_size_limit%&). If this option is false, only the
-message header is included. In the case of a non-SMTP message containing an
-error that is detected during reception, only those header lines preceding the
-point at which the error was detected are returned.
-.cindex "bounce message" "including original"
-
-.option bounce_return_linesize_limit main integer 998
-.cindex "size" "of bounce lines, limit"
-.cindex "bounce message" "line length limit"
-.cindex "limit" "bounce message line length"
-This option sets a limit in bytes on the line length of messages
-that are returned to senders due to delivery problems,
-when &%bounce_return_message%& is true.
-The default value corresponds to RFC limits.
-If the message being returned has lines longer than this value it is
-treated as if the &%bounce_return_size_limit%& (below) restriction was exceeded.
-
-The option also applies to bounces returned when an error is detected
-during reception of a message.
-In this case lines from the original are truncated.
-
-The option does not apply to messages generated by an &(autoreply)& transport.
-
-
-.option bounce_return_message main boolean true
-If this option is set false, none of the original message is included in
-bounce messages generated by Exim. See also &%bounce_return_size_limit%& and
-&%bounce_return_body%&.
-
-
-.option bounce_return_size_limit main integer 100K
-.cindex "size" "of bounce, limit"
-.cindex "bounce message" "size limit"
-.cindex "limit" "bounce message size"
-This option sets a limit in bytes on the size of messages that are returned to
-senders as part of bounce messages when &%bounce_return_message%& is true. The
-limit should be less than the value of the global &%message_size_limit%& and of
-any &%message_size_limit%& settings on transports, to allow for the bounce text
-that Exim generates. If this option is set to zero there is no limit.
-
-When the body of any message that is to be included in a bounce message is
-greater than the limit, it is truncated, and a comment pointing this out is
-added at the top. The actual cutoff may be greater than the value given, owing
-to the use of buffering for transferring the message in chunks (typically 8K in
-size). The idea is to save bandwidth on those undeliverable 15-megabyte
-messages.
-
-.option bounce_sender_authentication main string unset
-.cindex "bounce message" "sender authentication"
-.cindex "authentication" "bounce message"
-.cindex "AUTH" "on bounce message"
-This option provides an authenticated sender address that is sent with any
-bounce messages generated by Exim that are sent over an authenticated SMTP
-connection. A typical setting might be:
-.code
-bounce_sender_authentication = mailer-daemon@my.domain.example
-.endd
-which would cause bounce messages to be sent using the SMTP command:
-.code
-MAIL FROM:<> AUTH=mailer-daemon@my.domain.example
-.endd
-The value of &%bounce_sender_authentication%& must always be a complete email
-address.
-
-.option callout_domain_negative_expire main time 3h
-.cindex "caching" "callout timeouts"
-.cindex "callout" "caching timeouts"
-This option specifies the expiry time for negative callout cache data for a
-domain. See section &<<SECTcallver>>& for details of callout verification, and
-section &<<SECTcallvercache>>& for details of the caching.
-
-
-.option callout_domain_positive_expire main time 7d
-This option specifies the expiry time for positive callout cache data for a
-domain. See section &<<SECTcallver>>& for details of callout verification, and
-section &<<SECTcallvercache>>& for details of the caching.
-
-
-.option callout_negative_expire main time 2h
-This option specifies the expiry time for negative callout cache data for an
-address. See section &<<SECTcallver>>& for details of callout verification, and
-section &<<SECTcallvercache>>& for details of the caching.
-
-
-.option callout_positive_expire main time 24h
-This option specifies the expiry time for positive callout cache data for an
-address. See section &<<SECTcallver>>& for details of callout verification, and
-section &<<SECTcallvercache>>& for details of the caching.
-
-
-.option callout_random_local_part main string&!! "see below"
-This option defines the &"random"& local part that can be used as part of
-callout verification. The default value is
-.code
-$primary_hostname-$tod_epoch-testing
-.endd
-See section &<<CALLaddparcall>>& for details of how this value is used.
-
-
-.option check_log_inodes main integer 100
-See &%check_spool_space%& below.
-
-
-.option check_log_space main integer 10M
-See &%check_spool_space%& below.
-
-.oindex "&%check_rfc2047_length%&"
-.cindex "RFC 2047" "disabling length check"
-.option check_rfc2047_length main boolean true
-RFC 2047 defines a way of encoding non-ASCII characters in headers using a
-system of &"encoded words"&. The RFC specifies a maximum length for an encoded
-word; strings to be encoded that exceed this length are supposed to use
-multiple encoded words. By default, Exim does not recognize encoded words that
-exceed the maximum length. However, it seems that some software, in violation
-of the RFC, generates overlong encoded words. If &%check_rfc2047_length%& is
-set false, Exim recognizes encoded words of any length.
-
-
-.option check_spool_inodes main integer 100
-See &%check_spool_space%& below.
-
-
-.option check_spool_space main integer 10M
-.cindex "checking disk space"
-.cindex "disk space, checking"
-.cindex "spool directory" "checking space"
-The four &%check_...%& options allow for checking of disk resources before a
-message is accepted.
-
-.vindex "&$log_inodes$&"
-.vindex "&$log_space$&"
-.vindex "&$spool_inodes$&"
-.vindex "&$spool_space$&"
-When any of these options are nonzero, they apply to all incoming messages. If you
-want to apply different checks to different kinds of message, you can do so by
-testing the variables &$log_inodes$&, &$log_space$&, &$spool_inodes$&, and
-&$spool_space$& in an ACL with appropriate additional conditions.
-
-
-&%check_spool_space%& and &%check_spool_inodes%& check the spool partition if
-either value is greater than zero, for example:
-.code
-check_spool_space = 100M
-check_spool_inodes = 100
-.endd
-The spool partition is the one that contains the directory defined by
-SPOOL_DIRECTORY in &_Local/Makefile_&. It is used for holding messages in
-transit.
-
-&%check_log_space%& and &%check_log_inodes%&  check the partition in which log
-files are written if either is greater than zero. These should be set only if
-&%log_file_path%& and &%spool_directory%& refer to different partitions.
-
-If there is less space or fewer inodes than requested, Exim refuses to accept
-incoming mail. In the case of SMTP input this is done by giving a 452 temporary
-error response to the MAIL command. If ESMTP is in use and there was a
-SIZE parameter on the MAIL command, its value is added to the
-&%check_spool_space%& value, and the check is performed even if
-&%check_spool_space%& is zero, unless &%no_smtp_check_spool_space%& is set.
-
-The values for &%check_spool_space%& and &%check_log_space%& are held as a
-number of kilobytes (though specified in bytes).
-If a non-multiple of 1024 is specified, it is rounded up.
-
-For non-SMTP input and for batched SMTP input, the test is done at start-up; on
-failure a message is written to stderr and Exim exits with a non-zero code, as
-it obviously cannot send an error message of any kind.
-
-There is a slight performance penalty for these checks.
-Versions of Exim preceding 4.88 had these disabled by default;
-high-rate installations confident they will never run out of resources
-may wish to deliberately disable them.
-
-.option chunking_advertise_hosts main "host list&!!" *
-.cindex CHUNKING advertisement
-.cindex "RFC 3030" "CHUNKING"
-The CHUNKING extension (RFC3030) will be advertised in the EHLO message to
-these hosts.
-Hosts may use the BDAT command as an alternate to DATA.
-
-.option commandline_checks_require_admin main boolean &`false`&
-.cindex "restricting access to features"
-This option restricts various basic checking features to require an
-administrative user.
-This affects most of the &%-b*%& options, such as &%-be%&.
-
-.option debug_store main boolean &`false`&
-.cindex debugging "memory corruption"
-.cindex memory debugging
-This option, when true, enables extra checking in Exim's internal memory
-management.  For use when a memory corruption issue is being investigated,
-it should normally be left as default.
-
-.option daemon_smtp_ports main string &`smtp`&
-.cindex "port" "for daemon"
-.cindex "TCP/IP" "setting listening ports"
-This option specifies one or more default SMTP ports on which the Exim daemon
-listens. See chapter &<<CHAPinterfaces>>& for details of how it is used. For
-backward compatibility, &%daemon_smtp_port%& (singular) is a synonym.
-
-.option daemon_startup_retries main integer 9
-.cindex "daemon startup, retrying"
-This option, along with &%daemon_startup_sleep%&, controls the retrying done by
-the daemon at startup when it cannot immediately bind a listening socket
-(typically because the socket is already in use): &%daemon_startup_retries%&
-defines the number of retries after the first failure, and
-&%daemon_startup_sleep%& defines the length of time to wait between retries.
-
-.option daemon_startup_sleep main time 30s
-See &%daemon_startup_retries%&.
-
-.option delay_warning main "time list" 24h
-.cindex "warning of delay"
-.cindex "delay warning, specifying"
-.cindex "queue" "delay warning"
-When a message is delayed, Exim sends a warning message to the sender at
-intervals specified by this option. The data is a colon-separated list of times
-after which to send warning messages. If the value of the option is an empty
-string or a zero time, no warnings are sent. Up to 10 times may be given. If a
-message has been in the queue for longer than the last time, the last interval
-between the times is used to compute subsequent warning times. For example,
-with
-.code
-delay_warning = 4h:8h:24h
-.endd
-the first message is sent after 4 hours, the second after 8 hours, and
-the third one after 24 hours. After that, messages are sent every 16 hours,
-because that is the interval between the last two times on the list. If you set
-just one time, it specifies the repeat interval. For example, with:
-.code
-delay_warning = 6h
-.endd
-messages are repeated every six hours. To stop warnings after a given time, set
-a very large time at the end of the list. For example:
-.code
-delay_warning = 2h:12h:99d
-.endd
-Note that the option is only evaluated at the time a delivery attempt fails,
-which depends on retry and queue-runner configuration.
-Typically retries will be configured more frequently than warning messages.
-
-.option delay_warning_condition main string&!! "see below"
-.vindex "&$domain$&"
-The string is expanded at the time a warning message might be sent. If all the
-deferred addresses have the same domain, it is set in &$domain$& during the
-expansion. Otherwise &$domain$& is empty. If the result of the expansion is a
-forced failure, an empty string, or a string matching any of &"0"&, &"no"& or
-&"false"& (the comparison being done caselessly) then the warning message is
-not sent. The default is:
-.code
-delay_warning_condition = ${if or {\
-  { !eq{$h_list-id:$h_list-post:$h_list-subscribe:}{} }\
-  { match{$h_precedence:}{(?i)bulk|list|junk} }\
-  { match{$h_auto-submitted:}{(?i)auto-generated|auto-replied} }\
-  } {no}{yes}}
-.endd
-This suppresses the sending of warnings for messages that contain &'List-ID:'&,
-&'List-Post:'&, or &'List-Subscribe:'& headers, or have &"bulk"&, &"list"& or
-&"junk"& in a &'Precedence:'& header, or have &"auto-generated"& or
-&"auto-replied"& in an &'Auto-Submitted:'& header.
-
-.option deliver_drop_privilege main boolean false
-.cindex "unprivileged delivery"
-.cindex "delivery" "unprivileged"
-If this option is set true, Exim drops its root privilege at the start of a
-delivery process, and runs as the Exim user throughout. This severely restricts
-the kinds of local delivery that are possible, but is viable in certain types
-of configuration. There is a discussion about the use of root privilege in
-chapter &<<CHAPsecurity>>&.
-
-.option deliver_queue_load_max main fixed-point unset
-.cindex "load average"
-.cindex "queue runner" "abandoning"
-When this option is set, a queue run is abandoned if the system load average
-becomes greater than the value of the option. The option has no effect on
-ancient operating systems on which Exim cannot determine the load average.
-See also &%queue_only_load%& and &%smtp_load_reserve%&.
-
-
-.option delivery_date_remove main boolean true
-.cindex "&'Delivery-date:'& header line"
-Exim's transports have an option for adding a &'Delivery-date:'& header to a
-message when it is delivered, in exactly the same way as &'Return-path:'& is
-handled. &'Delivery-date:'& records the actual time of delivery. Such headers
-should not be present in incoming messages, and this option causes them to be
-removed at the time the message is received, to avoid any problems that might
-occur when a delivered message is subsequently sent on to some other recipient.
-
-.option disable_fsync main boolean false
-.cindex "&[fsync()]&, disabling"
-This option is available only if Exim was built with the compile-time option
-ENABLE_DISABLE_FSYNC. When this is not set, a reference to &%disable_fsync%& in
-a runtime configuration generates an &"unknown option"& error. You should not
-build Exim with ENABLE_DISABLE_FSYNC or set &%disable_fsync%& unless you
-really, really, really understand what you are doing. &'No pre-compiled
-distributions of Exim should ever make this option available.'&
-
-When &%disable_fsync%& is set true, Exim no longer calls &[fsync()]& to force
-updated files' data to be written to disc before continuing. Unexpected events
-such as crashes and power outages may cause data to be lost or scrambled.
-Here be Dragons. &*Beware.*&
-
-
-.option disable_ipv6 main boolean false
-.cindex "IPv6" "disabling"
-If this option is set true, even if the Exim binary has IPv6 support, no IPv6
-activities take place. AAAA records are never looked up, and any IPv6 addresses
-that are listed in &%local_interfaces%&, data for the &%manualroute%& router,
-etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
-to handle IPv6 literal addresses.
-
-
-.new
-.option dkim_verify_hashes main "string list" "sha256 : sha512"
-.cindex DKIM "selecting signature algorithms"
-This option gives a list of hash types which are acceptable in signatures,
-.wen
-and an order of processing.
-Signatures with algorithms not in the list will be ignored.
-
-Acceptable values include:
-.code
-sha1
-sha256
-sha512
-.endd
-
-Note that the acceptance of sha1 violates RFC 8301.
-
-.option dkim_verify_keytypes main "string list" "ed25519 : rsa"
-This option gives a list of key types which are acceptable in signatures,
-and an order of processing.
-Signatures with algorithms not in the list will be ignored.
-
-.option dkim_verify_minimal main boolean false
-If set to true, verification of signatures will terminate after the
-first success.
-
-.option dkim_verify_signers main "domain list&!!" $dkim_signers
-.cindex DKIM "controlling calls to the ACL"
-This option gives a list of DKIM domains for which the DKIM ACL is run.
-It is expanded after the message is received; by default it runs
-the ACL once for each signature in the message.
-See section &<<SECDKIMVFY>>&.
-
-
-.option dns_again_means_nonexist main "domain list&!!" unset
-.cindex "DNS" "&""try again""& response; overriding"
-DNS lookups give a &"try again"& response for the DNS errors
-&"non-authoritative host not found"& and &"SERVERFAIL"&. This can cause Exim to
-keep trying to deliver a message, or to give repeated temporary errors to
-incoming mail. Sometimes the effect is caused by a badly set up name server and
-may persist for a long time. If a domain which exhibits this problem matches
-anything in &%dns_again_means_nonexist%&, it is treated as if it did not exist.
-This option should be used with care. You can make it apply to reverse lookups
-by a setting such as this:
-.code
-dns_again_means_nonexist = *.in-addr.arpa
-.endd
-This option applies to all DNS lookups that Exim does. It also applies when the
-&[gethostbyname()]& or &[getipnodebyname()]& functions give temporary errors,
-since these are most likely to be caused by DNS lookup problems. The
-&(dnslookup)& router has some options of its own for controlling what happens
-when lookups for MX or SRV records give temporary errors. These more specific
-options are applied after this global option.
-
-.option dns_check_names_pattern main string "see below"
-.cindex "DNS" "pre-check of name syntax"
-When this option is set to a non-empty string, it causes Exim to check domain
-names for characters that are not allowed in host names before handing them to
-the DNS resolver, because some resolvers give temporary errors for names that
-contain unusual characters. If a domain name contains any unwanted characters,
-a &"not found"& result is forced, and the resolver is not called. The check is
-done by matching the domain name against a regular expression, which is the
-value of this option. The default pattern is
-.code
-dns_check_names_pattern = \
-  (?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9/-]*[^\W_])?)+$
-.endd
-which permits only letters, digits, slashes, and hyphens in components, but
-they must start and end with a letter or digit. Slashes are not, in fact,
-permitted in host names, but they are found in certain NS records (which can be
-accessed in Exim by using a &%dnsdb%& lookup). If you set
-&%allow_utf8_domains%&, you must modify this pattern, or set the option to an
-empty string.
-
-.option dns_csa_search_limit main integer 5
-This option controls the depth of parental searching for CSA SRV records in the
-DNS, as described in more detail in section &<<SECTverifyCSA>>&.
-
-.option dns_csa_use_reverse main boolean true
-This option controls whether or not an IP address, given as a CSA domain, is
-reversed and looked up in the reverse DNS, as described in more detail in
-section &<<SECTverifyCSA>>&.
-
-.option dns_cname_loops main integer 1
-.cindex DNS "CNAME following"
-This option controls the following of CNAME chains, needed if the resolver does
-not do it internally.
-As of 2018 most should, and the default can be left.
-If you have an ancient one, a value of 10 is likely needed.
-
-The default value of one CNAME-follow is needed
-thanks to the observed return for an MX request,
-given no MX presence but a CNAME to an A, of the CNAME.
-
-
-.option dns_dnssec_ok main integer -1
-.cindex "DNS" "resolver options"
-.cindex "DNS" "DNSSEC"
-If this option is set to a non-negative number then Exim will initialise the
-DNS resolver library to either use or not use DNSSEC, overriding the system
-default. A value of 0 coerces DNSSEC off, a value of 1 coerces DNSSEC on.
-
-If the resolver library does not support DNSSEC then this option has no effect.
-
-
-.option dns_ipv4_lookup main "domain list&!!" unset
-.cindex "IPv6" "DNS lookup for AAAA records"
-.cindex "DNS" "IPv6 lookup for AAAA records"
-.cindex DNS "IPv6 disabling"
-When Exim is compiled with IPv6 support and &%disable_ipv6%& is not set, it
-looks for IPv6 address records (AAAA records) as well as IPv4 address records
-(A records) when trying to find IP addresses for hosts, unless the host's
-domain matches this list.
-
-This is a fudge to help with name servers that give big delays or otherwise do
-not work for the AAAA record type. In due course, when the world's name
-servers have all been upgraded, there should be no need for this option.
-Note that all lookups, including those done for verification, are affected;
-this will result in verify failure for IPv6 connections or ones using names
-only valid for IPv6 addresses.
-
-
-.option dns_retrans main time 0s
-.cindex "DNS" "resolver options"
-.cindex timeout "dns lookup"
-.cindex "DNS" timeout
-The options &%dns_retrans%& and &%dns_retry%& can be used to set the
-retransmission and retry parameters for DNS lookups. Values of zero (the
-defaults) leave the system default settings unchanged. The first value is the
-time between retries, and the second is the number of retries. It isn't
-totally clear exactly how these settings affect the total time a DNS lookup may
-take. I haven't found any documentation about timeouts on DNS lookups; these
-parameter values are available in the external resolver interface structure,
-but nowhere does it seem to describe how they are used or what you might want
-to set in them.
-See also the &%slow_lookup_log%& option.
-
-
-.option dns_retry main integer 0
-See &%dns_retrans%& above.
-
-
-.option dns_trust_aa main "domain list&!!" unset
-.cindex "DNS" "resolver options"
-.cindex "DNS" "DNSSEC"
-If this option is set then lookup results marked with the AA bit
-(Authoritative Answer) are trusted the same way as if they were
-DNSSEC-verified. The authority section's name of the answer must
-match with this expanded domain list.
-
-Use this option only if you talk directly to a resolver that is
-authoritative for some zones and does not set the AD (Authentic Data)
-bit in the answer. Some DNS servers may have an configuration option to
-mark the answers from their own zones as verified (they set the AD bit).
-Others do not have this option. It is considered as poor practice using
-a resolver that is an authoritative server for some zones.
-
-Use this option only if you really have to (e.g. if you want
-to use DANE for remote delivery to a server that is listed in the DNS
-zones that your resolver is authoritative for).
-
-If the DNS answer packet has the AA bit set and contains resource record
-in the answer section, the name of the first NS record appearing in the
-authority section is compared against the list. If the answer packet is
-authoritative but the answer section is empty, the name of the first SOA
-record in the authoritative section is used instead.
-
-.cindex "DNS" "resolver options"
-.option dns_use_edns0 main integer -1
-.cindex "DNS" "resolver options"
-.cindex "DNS" "EDNS0"
-.cindex "DNS" "OpenBSD
-If this option is set to a non-negative number then Exim will initialise the
-DNS resolver library to either use or not use EDNS0 extensions, overriding
-the system default. A value of 0 coerces EDNS0 off, a value of 1 coerces EDNS0
-on.
-
-If the resolver library does not support EDNS0 then this option has no effect.
-
-OpenBSD's asr resolver routines are known to ignore the EDNS0 option; this
-means that DNSSEC will not work with Exim on that platform either, unless Exim
-is linked against an alternative DNS client library.
-
-
-.option drop_cr main boolean false
-This is an obsolete option that is now a no-op. It used to affect the way Exim
-handled CR and LF characters in incoming messages. What happens now is
-described in section &<<SECTlineendings>>&.
-
-.option dsn_advertise_hosts main "host list&!!" unset
-.cindex "bounce messages" "success"
-.cindex "DSN" "success"
-.cindex "Delivery Status Notification" "success"
-DSN extensions (RFC3461) will be advertised in the EHLO message to,
-and accepted from, these hosts.
-Hosts may use the NOTIFY and ENVID options on RCPT TO commands,
-and RET and ORCPT options on MAIL FROM commands.
-A NOTIFY=SUCCESS option requests success-DSN messages.
-A NOTIFY= option with no argument requests that no delay or failure DSNs
-are sent.
-
-.option dsn_from main "string&!!" "see below"
-.cindex "&'From:'& header line" "in bounces"
-.cindex "bounce messages" "&'From:'& line, specifying"
-This option can be used to vary the contents of &'From:'& header lines in
-bounces and other automatically generated messages (&"Delivery Status
-Notifications"& &-- hence the name of the option). The default setting is:
-.code
-dsn_from = Mail Delivery System <Mailer-Daemon@$qualify_domain>
-.endd
-The value is expanded every time it is needed. If the expansion fails, a
-panic is logged, and the default value is used.
-
-.option envelope_to_remove main boolean true
-.cindex "&'Envelope-to:'& header line"
-Exim's transports have an option for adding an &'Envelope-to:'& header to a
-message when it is delivered, in exactly the same way as &'Return-path:'& is
-handled. &'Envelope-to:'& records the original recipient address from the
-message's envelope that caused the delivery to happen. Such headers should not
-be present in incoming messages, and this option causes them to be removed at
-the time the message is received, to avoid any problems that might occur when a
-delivered message is subsequently sent on to some other recipient.
-
-
-.option errors_copy main "string list&!!" unset
-.cindex "bounce message" "copy to other address"
-.cindex "copy of bounce message"
-Setting this option causes Exim to send bcc copies of bounce messages that it
-generates to other addresses. &*Note*&: This does not apply to bounce messages
-coming from elsewhere. The value of the option is a colon-separated list of
-items. Each item consists of a pattern, terminated by white space, followed by
-a comma-separated list of email addresses. If a pattern contains spaces, it
-must be enclosed in double quotes.
-
-Each pattern is processed in the same way as a single item in an address list
-(see section &<<SECTaddresslist>>&). When a pattern matches the recipient of
-the bounce message, the message is copied to the addresses on the list. The
-items are scanned in order, and once a matching one is found, no further items
-are examined. For example:
-.code
-errors_copy = spqr@mydomain   postmaster@mydomain.example :\
-              rqps@mydomain   hostmaster@mydomain.example,\
-                              postmaster@mydomain.example
-.endd
-.vindex "&$domain$&"
-.vindex "&$local_part$&"
-The address list is expanded before use. The expansion variables &$local_part$&
-and &$domain$& are set from the original recipient of the error message, and if
-there was any wildcard matching in the pattern, the expansion
-.cindex "numerical variables (&$1$& &$2$& etc)" "in &%errors_copy%&"
-variables &$0$&, &$1$&, etc. are set in the normal way.
-
-
-.option errors_reply_to main string unset
-.cindex "bounce message" "&'Reply-to:'& in"
-By default, Exim's bounce and delivery warning messages contain the header line
-.display
-&`From: Mail Delivery System <Mailer-Daemon@`&&'qualify-domain'&&`>`&
-.endd
-.oindex &%quota_warn_message%&
-where &'qualify-domain'& is the value of the &%qualify_domain%& option.
-A warning message that is generated by the &%quota_warn_message%& option in an
-&(appendfile)& transport may contain its own &'From:'& header line that
-overrides the default.
-
-Experience shows that people reply to bounce messages. If the
-&%errors_reply_to%& option is set, a &'Reply-To:'& header is added to bounce
-and warning messages. For example:
-.code
-errors_reply_to = postmaster@my.domain.example
-.endd
-The value of the option is not expanded. It must specify a valid RFC 2822
-address. However, if a warning message that is generated by the
-&%quota_warn_message%& option in an &(appendfile)& transport contain its
-own &'Reply-To:'& header line, the value of the &%errors_reply_to%& option is
-not used.
-
-
-.option event_action main string&!! unset
-.cindex events
-This option declares a string to be expanded for Exim's events mechanism.
-For details see chapter &<<CHAPevents>>&.
-
-
-.option exim_group main string "compile-time configured"
-.cindex "gid (group id)" "Exim's own"
-.cindex "Exim group"
-This option changes the gid under which Exim runs when it gives up root
-privilege. The default value is compiled into the binary. The value of this
-option is used only when &%exim_user%& is also set. Unless it consists entirely
-of digits, the string is looked up using &[getgrnam()]&, and failure causes a
-configuration error. See chapter &<<CHAPsecurity>>& for a discussion of
-security issues.
-
-
-.option exim_path main string "see below"
-.cindex "Exim binary, path name"
-This option specifies the path name of the Exim binary, which is used when Exim
-needs to re-exec itself. The default is set up to point to the file &'exim'& in
-the directory configured at compile time by the BIN_DIRECTORY setting. It
-is necessary to change &%exim_path%& if, exceptionally, Exim is run from some
-other place.
-&*Warning*&: Do not use a macro to define the value of this option, because
-you will break those Exim utilities that scan the configuration file to find
-where the binary is. (They then use the &%-bP%& option to extract option
-settings such as the value of &%spool_directory%&.)
-
-
-.option exim_user main string "compile-time configured"
-.cindex "uid (user id)" "Exim's own"
-.cindex "Exim user"
-This option changes the uid under which Exim runs when it gives up root
-privilege. The default value is compiled into the binary. Ownership of the run
-time configuration file and the use of the &%-C%& and &%-D%& command line
-options is checked against the values in the binary, not what is set here.
-
-Unless it consists entirely of digits, the string is looked up using
-&[getpwnam()]&, and failure causes a configuration error. If &%exim_group%& is
-not also supplied, the gid is taken from the result of &[getpwnam()]& if it is
-used. See chapter &<<CHAPsecurity>>& for a discussion of security issues.
-
-
-.option exim_version main string "current version"
-.cindex "Exim version"
-.cindex customizing "version number"
-.cindex "version number of Exim" override
-This option overrides the &$version_number$&/&$exim_version$& that Exim reports in
-various places.  Use with care; this may fool stupid security scanners.
-
-
-.option extra_local_interfaces main "string list" unset
-This option defines network interfaces that are to be considered local when
-routing, but which are not used for listening by the daemon. See section
-&<<SECTreclocipadd>>& for details.
-
-
-. Allow this long option name to split; give it unsplit as a fifth argument
-. for the automatic .oindex that is generated by .option.
-
-.option "extract_addresses_remove_arguments" main boolean true &&&
-         extract_addresses_remove_arguments
-.oindex "&%-t%&"
-.cindex "command line" "addresses with &%-t%&"
-.cindex "Sendmail compatibility" "&%-t%& option"
-According to some Sendmail documentation (Sun, IRIX, HP-UX), if any addresses
-are present on the command line when the &%-t%& option is used to build an
-envelope from a message's &'To:'&, &'Cc:'& and &'Bcc:'& headers, the command
-line addresses are removed from the recipients list. This is also how Smail
-behaves. However, other Sendmail documentation (the O'Reilly book) states that
-command line addresses are added to those obtained from the header lines. When
-&%extract_addresses_remove_arguments%& is true (the default), Exim subtracts
-argument headers. If it is set false, Exim adds rather than removes argument
-addresses.
-
-
-.option finduser_retries main integer 0
-.cindex "NIS, retrying user lookups"
-On systems running NIS or other schemes in which user and group information is
-distributed from a remote system, there can be times when &[getpwnam()]& and
-related functions fail, even when given valid data, because things time out.
-Unfortunately these failures cannot be distinguished from genuine &"not found"&
-errors. If &%finduser_retries%& is set greater than zero, Exim will try that
-many extra times to find a user or a group, waiting for one second between
-retries.
-
-.cindex "&_/etc/passwd_&" "multiple reading of"
-You should not set this option greater than zero if your user information is in
-a traditional &_/etc/passwd_& file, because it will cause Exim needlessly to
-search the file multiple times for non-existent users, and also cause delay.
-
-
-
-.option freeze_tell main "string list, comma separated" unset
-.cindex "freezing messages" "sending a message when freezing"
-On encountering certain errors, or when configured to do so in a system filter,
-ACL, or special router, Exim freezes a message. This means that no further
-delivery attempts take place until an administrator thaws the message, or the
-&%auto_thaw%&, &%ignore_bounce_errors_after%&, or &%timeout_frozen_after%&
-feature cause it to be processed. If &%freeze_tell%& is set, Exim generates a
-warning message whenever it freezes something, unless the message it is
-freezing is a locally-generated bounce message. (Without this exception there
-is the possibility of looping.) The warning message is sent to the addresses
-supplied as the comma-separated value of this option. If several of the
-message's addresses cause freezing, only a single message is sent. If the
-freezing was automatic, the reason(s) for freezing can be found in the message
-log. If you configure freezing in a filter or ACL, you must arrange for any
-logging that you require.
-
-
-.option gecos_name main string&!! unset
-.cindex "HP-UX"
-.cindex "&""gecos""& field, parsing"
-Some operating systems, notably HP-UX, use the &"gecos"& field in the system
-password file to hold other information in addition to users' real names. Exim
-looks up this field for use when it is creating &'Sender:'& or &'From:'&
-headers. If either &%gecos_pattern%& or &%gecos_name%& are unset, the contents
-of the field are used unchanged, except that, if an ampersand is encountered,
-it is replaced by the user's login name with the first character forced to
-upper case, since this is a convention that is observed on many systems.
-
-When these options are set, &%gecos_pattern%& is treated as a regular
-expression that is to be applied to the field (again with && replaced by the
-login name), and if it matches, &%gecos_name%& is expanded and used as the
-user's name.
-
-.cindex "numerical variables (&$1$& &$2$& etc)" "in &%gecos_name%&"
-Numeric variables such as &$1$&, &$2$&, etc. can be used in the expansion to
-pick up sub-fields that were matched by the pattern. In HP-UX, where the user's
-name terminates at the first comma, the following can be used:
-.code
-gecos_pattern = ([^,]*)
-gecos_name = $1
-.endd
-
-.option gecos_pattern main string unset
-See &%gecos_name%& above.
-
-
-.option gnutls_compat_mode main boolean unset
-This option controls whether GnuTLS is used in compatibility mode in an Exim
-server. This reduces security slightly, but improves interworking with older
-implementations of TLS.
-
-
-.option gnutls_allow_auto_pkcs11 main boolean unset
-This option will let GnuTLS (2.12.0 or later) autoload PKCS11 modules with
-the p11-kit configuration files in &_/etc/pkcs11/modules/_&.
-
-See
-&url(https://www.gnutls.org/manual/gnutls.html#Smart-cards-and-HSMs)
-for documentation.
-
-
-
-.option headers_charset main string "see below"
-This option sets a default character set for translating from encoded MIME
-&"words"& in header lines, when referenced by an &$h_xxx$& expansion item. The
-default is the value of HEADERS_CHARSET in &_Local/Makefile_&. The
-ultimate default is ISO-8859-1. For more details see the description of header
-insertions in section &<<SECTexpansionitems>>&.
-
-
-
-.option header_maxsize main integer "see below"
-.cindex "header section" "maximum size of"
-.cindex "limit" "size of message header section"
-This option controls the overall maximum size of a message's header
-section. The default is the value of HEADER_MAXSIZE in
-&_Local/Makefile_&; the default for that is 1M. Messages with larger header
-sections are rejected.
-
-
-.option header_line_maxsize main integer 0
-.cindex "header lines" "maximum size of"
-.cindex "limit" "size of one header line"
-This option limits the length of any individual header line in a message, after
-all the continuations have been joined together. Messages with individual
-header lines that are longer than the limit are rejected. The default value of
-zero means &"no limit"&.
-
-
-
-
-.option helo_accept_junk_hosts main "host list&!!" unset
-.cindex "HELO" "accepting junk data"
-.cindex "EHLO" "accepting junk data"
-Exim checks the syntax of HELO and EHLO commands for incoming SMTP
-mail, and gives an error response for invalid data. Unfortunately, there are
-some SMTP clients that send syntactic junk. They can be accommodated by setting
-this option. Note that this is a syntax check only. See &%helo_verify_hosts%&
-if you want to do semantic checking.
-See also &%helo_allow_chars%& for a way of extending the permitted character
-set.
-
-
-.option helo_allow_chars main string unset
-.cindex "HELO" "underscores in"
-.cindex "EHLO" "underscores in"
-.cindex "underscore in EHLO/HELO"
-This option can be set to a string of rogue characters that are permitted in
-all EHLO and HELO names in addition to the standard letters, digits,
-hyphens, and dots. If you really must allow underscores, you can set
-.code
-helo_allow_chars = _
-.endd
-Note that the value is one string, not a list.
-
-
-.option helo_lookup_domains main "domain list&!!" &`@:@[]`&
-.cindex "HELO" "forcing reverse lookup"
-.cindex "EHLO" "forcing reverse lookup"
-If the domain given by a client in a HELO or EHLO command matches this
-list, a reverse lookup is done in order to establish the host's true name. The
-default forces a lookup if the client host gives the server's name or any of
-its IP addresses (in brackets), something that broken clients have been seen to
-do.
-
-
-.option helo_try_verify_hosts main "host list&!!" unset
-.cindex "HELO verifying" "optional"
-.cindex "EHLO" "verifying, optional"
-By default, Exim just checks the syntax of HELO and EHLO commands (see
-&%helo_accept_junk_hosts%& and &%helo_allow_chars%&). However, some sites like
-to do more extensive checking of the data supplied by these commands. The ACL
-condition &`verify = helo`& is provided to make this possible.
-Formerly, it was necessary also to set this option (&%helo_try_verify_hosts%&)
-to force the check to occur. From release 4.53 onwards, this is no longer
-necessary. If the check has not been done before &`verify = helo`& is
-encountered, it is done at that time. Consequently, this option is obsolete.
-Its specification is retained here for backwards compatibility.
-
-When an EHLO or HELO command is received, if the calling host matches
-&%helo_try_verify_hosts%&, Exim checks that the host name given in the HELO or
-EHLO command either:
-
-.ilist
-is an IP literal matching the calling address of the host, or
-.next
-.cindex "DNS" "reverse lookup"
-.cindex "reverse DNS lookup"
-matches the host name that Exim obtains by doing a reverse lookup of the
-calling host address, or
-.next
-when looked up in DNS yields the calling host address.
-.endlist
-
-However, the EHLO or HELO command is not rejected if any of the checks
-fail. Processing continues, but the result of the check is remembered, and can
-be detected later in an ACL by the &`verify = helo`& condition.
-
-If DNS was used for successful verification, the variable
-.cindex "DNS" "DNSSEC"
-&$helo_verify_dnssec$& records the DNSSEC status of the lookups.
-
-.option helo_verify_hosts main "host list&!!" unset
-.cindex "HELO verifying" "mandatory"
-.cindex "EHLO" "verifying, mandatory"
-Like &%helo_try_verify_hosts%&, this option is obsolete, and retained only for
-backwards compatibility. For hosts that match this option, Exim checks the host
-name given in the HELO or EHLO in the same way as for
-&%helo_try_verify_hosts%&. If the check fails, the HELO or EHLO command is
-rejected with a 550 error, and entries are written to the main and reject logs.
-If a MAIL command is received before EHLO or HELO, it is rejected with a 503
-error.
-
-.option hold_domains main "domain list&!!" unset
-.cindex "domain" "delaying delivery"
-.cindex "delivery" "delaying certain domains"
-This option allows mail for particular domains to be held in the queue
-manually. The option is overridden if a message delivery is forced with the
-&%-M%&, &%-qf%&, &%-Rf%& or &%-Sf%& options, and also while testing or
-verifying addresses using &%-bt%& or &%-bv%&. Otherwise, if a domain matches an
-item in &%hold_domains%&, no routing or delivery for that address is done, and
-it is deferred every time the message is looked at.
-
-This option is intended as a temporary operational measure for delaying the
-delivery of mail while some problem is being sorted out, or some new
-configuration tested. If you just want to delay the processing of some
-domains until a queue run occurs, you should use &%queue_domains%& or
-&%queue_smtp_domains%&, not &%hold_domains%&.
-
-A setting of &%hold_domains%& does not override Exim's code for removing
-messages from the queue if they have been there longer than the longest retry
-time in any retry rule. If you want to hold messages for longer than the normal
-retry times, insert a dummy retry rule with a long retry time.
-
-
-.option host_lookup main "host list&!!" unset
-.cindex "host name" "lookup, forcing"
-Exim does not look up the name of a calling host from its IP address unless it
-is required to compare against some host list, or the host matches
-&%helo_try_verify_hosts%& or &%helo_verify_hosts%&, or the host matches this
-option (which normally contains IP addresses rather than host names). The
-default configuration file contains
-.code
-host_lookup = *
-.endd
-which causes a lookup to happen for all hosts. If the expense of these lookups
-is felt to be too great, the setting can be changed or removed.
-
-After a successful reverse lookup, Exim does a forward lookup on the name it
-has obtained, to verify that it yields the IP address that it started with. If
-this check fails, Exim behaves as if the name lookup failed.
-
-.vindex "&$host_lookup_failed$&"
-.vindex "&$sender_host_name$&"
-After any kind of failure, the host name (in &$sender_host_name$&) remains
-unset, and &$host_lookup_failed$& is set to the string &"1"&. See also
-&%dns_again_means_nonexist%&, &%helo_lookup_domains%&, and
-&`verify = reverse_host_lookup`& in ACLs.
-
-
-.option host_lookup_order main "string list" &`bydns:byaddr`&
-This option specifies the order of different lookup methods when Exim is trying
-to find a host name from an IP address. The default is to do a DNS lookup
-first, and then to try a local lookup (using &[gethostbyaddr()]& or equivalent)
-if that fails. You can change the order of these lookups, or omit one entirely,
-if you want.
-
-&*Warning*&: The &"byaddr"& method does not always yield aliases when there are
-multiple PTR records in the DNS and the IP address is not listed in
-&_/etc/hosts_&. Different operating systems give different results in this
-case. That is why the default tries a DNS lookup first.
-
-
-
-.option host_reject_connection main "host list&!!" unset
-.cindex "host" "rejecting connections from"
-If this option is set, incoming SMTP calls from the hosts listed are rejected
-as soon as the connection is made.
-This option is obsolete, and retained only for backward compatibility, because
-nowadays the ACL specified by &%acl_smtp_connect%& can also reject incoming
-connections immediately.
-
-The ability to give an immediate rejection (either by this option or using an
-ACL) is provided for use in unusual cases. Many hosts will just try again,
-sometimes without much delay. Normally, it is better to use an ACL to reject
-incoming messages at a later stage, such as after RCPT commands. See
-chapter &<<CHAPACL>>&.
-
-
-.option hosts_connection_nolog main "host list&!!" unset
-.cindex "host" "not logging connections from"
-This option defines a list of hosts for which connection logging does not
-happen, even though the &%smtp_connection%& log selector is set. For example,
-you might want not to log SMTP connections from local processes, or from
-127.0.0.1, or from your local LAN. This option is consulted in the main loop of
-the daemon; you should therefore strive to restrict its value to a short inline
-list of IP addresses and networks. To disable logging SMTP connections from
-local processes, you must create a host list with an empty item. For example:
-.code
-hosts_connection_nolog = :
-.endd
-If the &%smtp_connection%& log selector is not set, this option has no effect.
-
-
-
-.option hosts_proxy main "host list&!!" unset
-.cindex proxy "proxy protocol"
-This option enables use of Proxy Protocol proxies for incoming
-connections.  For details see section &<<SECTproxyInbound>>&.
-
-
-.option hosts_treat_as_local main "domain list&!!" unset
-.cindex "local host" "domains treated as"
-.cindex "host" "treated as local"
-If this option is set, any host names that match the domain list are treated as
-if they were the local host when Exim is scanning host lists obtained from MX
-records
-or other sources. Note that the value of this option is a domain list, not a
-host list, because it is always used to check host names, not IP addresses.
-
-This option also applies when Exim is matching the special items
-&`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`& in a domain list (see
-section &<<SECTdomainlist>>&), and when checking the &%hosts%& option in the
-&(smtp)& transport for the local host (see the &%allow_localhost%& option in
-that transport). See also &%local_interfaces%&, &%extra_local_interfaces%&, and
-chapter &<<CHAPinterfaces>>&, which contains a discussion about local network
-interfaces and recognizing the local host.
-
-
-.option ibase_servers main "string list" unset
-.cindex "InterBase" "server list"
-This option provides a list of InterBase servers and associated connection data,
-to be used in conjunction with &(ibase)& lookups (see section &<<SECID72>>&).
-The option is available only if Exim has been built with InterBase support.
-
-
-
-.option ignore_bounce_errors_after main time 10w
-.cindex "bounce message" "discarding"
-.cindex "discarding bounce message"
-This option affects the processing of bounce messages that cannot be delivered,
-that is, those that suffer a permanent delivery failure. (Bounce messages that
-suffer temporary delivery failures are of course retried in the usual way.)
-
-After a permanent delivery failure, bounce messages are frozen,
-because there is no sender to whom they can be returned. When a frozen bounce
-message has been in the queue for more than the given time, it is unfrozen at
-the next queue run, and a further delivery is attempted. If delivery fails
-again, the bounce message is discarded. This makes it possible to keep failed
-bounce messages around for a shorter time than the normal maximum retry time
-for frozen messages. For example,
-.code
-ignore_bounce_errors_after = 12h
-.endd
-retries failed bounce message deliveries after 12 hours, discarding any further
-failures. If the value of this option is set to a zero time period, bounce
-failures are discarded immediately. Setting a very long time (as in the default
-value) has the effect of disabling this option. For ways of automatically
-dealing with other kinds of frozen message, see &%auto_thaw%& and
-&%timeout_frozen_after%&.
-
-
-.option ignore_fromline_hosts main "host list&!!" unset
-.cindex "&""From""& line"
-.cindex "UUCP" "&""From""& line"
-Some broken SMTP clients insist on sending a UUCP-like &"From&~"& line before
-the headers of a message. By default this is treated as the start of the
-message's body, which means that any following headers are not recognized as
-such. Exim can be made to ignore it by setting &%ignore_fromline_hosts%& to
-match those hosts that insist on sending it. If the sender is actually a local
-process rather than a remote host, and is using &%-bs%& to inject the messages,
-&%ignore_fromline_local%& must be set to achieve this effect.
-
-
-.option ignore_fromline_local main boolean false
-See &%ignore_fromline_hosts%& above.
-
-.option keep_environment main "string list" unset
-.cindex "environment" "values from"
-This option contains a string list of environment variables to keep.
-You have to trust these variables or you have to be sure that
-these variables do not impose any security risk. Keep in mind that
-during the startup phase Exim is running with an effective UID 0 in most
-installations. As the default value is an empty list, the default
-environment for using libraries, running embedded Perl code, or running
-external binaries is empty, and does not not even contain PATH or HOME.
-
-Actually the list is interpreted as a list of patterns
-(&<<SECTlistexpand>>&), except that it is not expanded first.
-
-WARNING: Macro substitution is still done first, so having a macro
-FOO and having FOO_HOME in your &%keep_environment%& option may have
-unexpected results. You may work around this using a regular expression
-that does not match the macro name: ^[F]OO_HOME$.
-
-Current versions of Exim issue a warning during startup if you do not mention
-&%keep_environment%& in your runtime configuration file and if your
-current environment is not empty. Future versions may not issue that warning
-anymore.
-
-See the &%add_environment%& main config option for a way to set
-environment variables to a fixed value.  The environment for &(pipe)&
-transports is handled separately, see section &<<SECTpipeenv>>& for
-details.
-
-
-.option keep_malformed main time 4d
-This option specifies the length of time to keep messages whose spool files
-have been corrupted in some way. This should, of course, never happen. At the
-next attempt to deliver such a message, it gets removed. The incident is
-logged.
-
-
-.option ldap_ca_cert_dir main string unset
-.cindex "LDAP", "TLS CA certificate directory"
-.cindex certificate "directory for LDAP"
-This option indicates which directory contains CA certificates for verifying
-a TLS certificate presented by an LDAP server.
-While Exim does not provide a default value, your SSL library may.
-Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
-and constrained to be a directory.
-
-
-.option ldap_ca_cert_file main string unset
-.cindex "LDAP", "TLS CA certificate file"
-.cindex certificate "file for LDAP"
-This option indicates which file contains CA certificates for verifying
-a TLS certificate presented by an LDAP server.
-While Exim does not provide a default value, your SSL library may.
-Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
-and constrained to be a file.
-
-
-.option ldap_cert_file main string unset
-.cindex "LDAP" "TLS client certificate file"
-.cindex certificate "file for LDAP"
-This option indicates which file contains an TLS client certificate which
-Exim should present to the LDAP server during TLS negotiation.
-Should be used together with &%ldap_cert_key%&.
-
-
-.option ldap_cert_key main string unset
-.cindex "LDAP" "TLS client key file"
-.cindex certificate "key for LDAP"
-This option indicates which file contains the secret/private key to use
-to prove identity to the LDAP server during TLS negotiation.
-Should be used together with &%ldap_cert_file%&, which contains the
-identity to be proven.
-
-
-.option ldap_cipher_suite main string unset
-.cindex "LDAP" "TLS cipher suite"
-This controls the TLS cipher-suite negotiation during TLS negotiation with
-the LDAP server.  See &<<SECTreqciphssl>>& for more details of the format of
-cipher-suite options with OpenSSL (as used by LDAP client libraries).
-
-
-.option ldap_default_servers main "string list" unset
-.cindex "LDAP" "default servers"
-This option provides a list of LDAP servers which are tried in turn when an
-LDAP query does not contain a server. See section &<<SECTforldaque>>& for
-details of LDAP queries. This option is available only when Exim has been built
-with LDAP support.
-
-
-.option ldap_require_cert main string unset.
-.cindex "LDAP" "policy for LDAP server TLS cert presentation"
-This should be one of the values "hard", "demand", "allow", "try" or "never".
-A value other than one of these is interpreted as "never".
-See the entry "TLS_REQCERT" in your system man page for ldap.conf(5).
-Although Exim does not set a default, the LDAP library probably defaults
-to hard/demand.
-
-
-.option ldap_start_tls main boolean false
-.cindex "LDAP" "whether or not to negotiate TLS"
-If set, Exim will attempt to negotiate TLS with the LDAP server when
-connecting on a regular LDAP port.  This is the LDAP equivalent of SMTP's
-"STARTTLS".  This is distinct from using "ldaps", which is the LDAP form
-of SSL-on-connect.
-In the event of failure to negotiate TLS, the action taken is controlled
-by &%ldap_require_cert%&.
-This option is ignored for &`ldapi`& connections.
-
-
-.option ldap_version main integer unset
-.cindex "LDAP" "protocol version, forcing"
-This option can be used to force Exim to set a specific protocol version for
-LDAP. If it option is unset, it is shown by the &%-bP%& command line option as
--1. When this is the case, the default is 3 if LDAP_VERSION3 is defined in
-the LDAP headers; otherwise it is 2. This option is available only when Exim
-has been built with LDAP support.
-
-
-
-.option local_from_check main boolean true
-.cindex "&'Sender:'& header line" "disabling addition of"
-.cindex "&'From:'& header line" "disabling checking of"
-When a message is submitted locally (that is, not over a TCP/IP connection) by
-an untrusted user, Exim removes any existing &'Sender:'& header line, and
-checks that the &'From:'& header line matches the login of the calling user and
-the domain specified by &%qualify_domain%&.
-
-&*Note*&: An unqualified address (no domain) in the &'From:'& header in a
-locally submitted message is automatically qualified by Exim, unless the
-&%-bnq%& command line option is used.
-
-You can use &%local_from_prefix%& and &%local_from_suffix%& to permit affixes
-on the local part. If the &'From:'& header line does not match, Exim adds a
-&'Sender:'& header with an address constructed from the calling user's login
-and the default qualify domain.
-
-If &%local_from_check%& is set false, the &'From:'& header check is disabled,
-and no &'Sender:'& header is ever added. If, in addition, you want to retain
-&'Sender:'& header lines supplied by untrusted users, you must also set
-&%local_sender_retain%& to be true.
-
-.cindex "envelope from"
-.cindex "envelope sender"
-These options affect only the header lines in the message. The envelope sender
-is still forced to be the login id at the qualify domain unless
-&%untrusted_set_sender%& permits the user to supply an envelope sender.
-
-For messages received over TCP/IP, an ACL can specify &"submission mode"& to
-request similar header line checking. See section &<<SECTthesenhea>>&, which
-has more details about &'Sender:'& processing.
-
-
-
-
-.option local_from_prefix main string unset
-When Exim checks the &'From:'& header line of locally submitted messages for
-matching the login id (see &%local_from_check%& above), it can be configured to
-ignore certain prefixes and suffixes in the local part of the address. This is
-done by setting &%local_from_prefix%& and/or &%local_from_suffix%& to
-appropriate lists, in the same form as the &%local_part_prefix%& and
-&%local_part_suffix%& router options (see chapter &<<CHAProutergeneric>>&). For
-example, if
-.code
-local_from_prefix = *-
-.endd
-is set, a &'From:'& line containing
-.code
-From: anything-user@your.domain.example
-.endd
-will not cause a &'Sender:'& header to be added if &'user@your.domain.example'&
-matches the actual sender address that is constructed from the login name and
-qualify domain.
-
-
-.option local_from_suffix main string unset
-See &%local_from_prefix%& above.
-
-
-.option local_interfaces main "string list" "see below"
-This option controls which network interfaces are used by the daemon for
-listening; they are also used to identify the local host when routing. Chapter
-&<<CHAPinterfaces>>& contains a full description of this option and the related
-options &%daemon_smtp_ports%&, &%extra_local_interfaces%&,
-&%hosts_treat_as_local%&, and &%tls_on_connect_ports%&. The default value for
-&%local_interfaces%& is
-.code
-local_interfaces = 0.0.0.0
-.endd
-when Exim is built without IPv6 support; otherwise it is
-.code
-local_interfaces = <; ::0 ; 0.0.0.0
-.endd
-
-.option local_scan_timeout main time 5m
-.cindex "timeout" "for &[local_scan()]& function"
-.cindex "&[local_scan()]& function" "timeout"
-This timeout applies to the &[local_scan()]& function (see chapter
-&<<CHAPlocalscan>>&). Zero means &"no timeout"&. If the timeout is exceeded,
-the incoming message is rejected with a temporary error if it is an SMTP
-message. For a non-SMTP message, the message is dropped and Exim ends with a
-non-zero code. The incident is logged on the main and reject logs.
-
-
-
-.option local_sender_retain main boolean false
-.cindex "&'Sender:'& header line" "retaining from local submission"
-When a message is submitted locally (that is, not over a TCP/IP connection) by
-an untrusted user, Exim removes any existing &'Sender:'& header line. If you
-do not want this to happen, you must set &%local_sender_retain%&, and you must
-also set &%local_from_check%& to be false (Exim will complain if you do not).
-See also the ACL modifier &`control = suppress_local_fixups`&. Section
-&<<SECTthesenhea>>& has more details about &'Sender:'& processing.
-
-
-
-
-.option localhost_number main string&!! unset
-.cindex "host" "locally unique number for"
-.cindex "message ids" "with multiple hosts"
-.vindex "&$localhost_number$&"
-Exim's message ids are normally unique only within the local host. If
-uniqueness among a set of hosts is required, each host must set a different
-value for the &%localhost_number%& option. The string is expanded immediately
-after reading the configuration file (so that a number can be computed from the
-host name, for example) and the result of the expansion must be a number in the
-range 0&--16 (or 0&--10 on operating systems with case-insensitive file
-systems). This is available in subsequent string expansions via the variable
-&$localhost_number$&. When &%localhost_number is set%&, the final two
-characters of the message id, instead of just being a fractional part of the
-time, are computed from the time and the local host number as described in
-section &<<SECTmessiden>>&.
-
-
-
-.option log_file_path main "string list&!!" "set at compile time"
-.cindex "log" "file path for"
-This option sets the path which is used to determine the names of Exim's log
-files, or indicates that logging is to be to syslog, or both. It is expanded
-when Exim is entered, so it can, for example, contain a reference to the host
-name. If no specific path is set for the log files at compile or runtime,
-or if the option is unset at runtime (i.e.  &`log_file_path = `&)
-they are written in a sub-directory called &_log_& in Exim's spool directory.
-A path must start with a slash.
-To send to syslog, use the word &"syslog"&.
-Chapter &<<CHAPlog>>& contains further details about Exim's logging, and
-section &<<SECTwhelogwri>>& describes how the contents of &%log_file_path%& are
-used. If this string is fixed at your installation (contains no expansion
-variables) it is recommended that you do not set this option in the
-configuration file, but instead supply the path using LOG_FILE_PATH in
-&_Local/Makefile_& so that it is available to Exim for logging errors detected
-early on &-- in particular, failure to read the configuration file.
-
-
-.option log_selector main string unset
-.cindex "log" "selectors"
-This option can be used to reduce or increase the number of things that Exim
-writes to its log files. Its argument is made up of names preceded by plus or
-minus characters. For example:
-.code
-log_selector = +arguments -retry_defer
-.endd
-A list of possible names and what they control is given in the chapter on
-logging, in section &<<SECTlogselector>>&.
-
-
-.option log_timezone main boolean false
-.cindex "log" "timezone for entries"
-.vindex "&$tod_log$&"
-.vindex "&$tod_zone$&"
-By default, the timestamps on log lines are in local time without the
-timezone. This means that if your timezone changes twice a year, the timestamps
-in log lines are ambiguous for an hour when the clocks go back. One way of
-avoiding this problem is to set the timezone to UTC. An alternative is to set
-&%log_timezone%& true. This turns on the addition of the timezone offset to
-timestamps in log lines. Turning on this option can add quite a lot to the size
-of log files because each line is extended by 6 characters. Note that the
-&$tod_log$& variable contains the log timestamp without the zone, but there is
-another variable called &$tod_zone$& that contains just the timezone offset.
-
-
-.option lookup_open_max main integer 25
-.cindex "too many open files"
-.cindex "open files, too many"
-.cindex "file" "too many open"
-.cindex "lookup" "maximum open files"
-.cindex "limit" "open files for lookups"
-This option limits the number of simultaneously open files for single-key
-lookups that use regular files (that is, &(lsearch)&, &(dbm)&, and &(cdb)&).
-Exim normally keeps these files open during routing, because often the same
-file is required several times. If the limit is reached, Exim closes the least
-recently used file. Note that if you are using the &'ndbm'& library, it
-actually opens two files for each logical DBM database, though it still counts
-as one for the purposes of &%lookup_open_max%&. If you are getting &"too many
-open files"& errors with NDBM, you need to reduce the value of
-&%lookup_open_max%&.
-
-
-.option max_username_length main integer 0
-.cindex "length of login name"
-.cindex "user name" "maximum length"
-.cindex "limit" "user name length"
-Some operating systems are broken in that they truncate long arguments to
-&[getpwnam()]& to eight characters, instead of returning &"no such user"&. If
-this option is set greater than zero, any attempt to call &[getpwnam()]& with
-an argument that is longer behaves as if &[getpwnam()]& failed.
-
-
-.option message_body_newlines main bool false
-.cindex "message body" "newlines in variables"
-.cindex "newline" "in message body variables"
-.vindex "&$message_body$&"
-.vindex "&$message_body_end$&"
-By default, newlines in the message body are replaced by spaces when setting
-the &$message_body$& and &$message_body_end$& expansion variables. If this
-option is set true, this no longer happens.
-
-
-.option message_body_visible main integer 500
-.cindex "body of message" "visible size"
-.cindex "message body" "visible size"
-.vindex "&$message_body$&"
-.vindex "&$message_body_end$&"
-This option specifies how much of a message's body is to be included in the
-&$message_body$& and &$message_body_end$& expansion variables.
-
-
-.option message_id_header_domain main string&!! unset
-.cindex "&'Message-ID:'& header line"
-If this option is set, the string is expanded and used as the right hand side
-(domain) of the &'Message-ID:'& header that Exim creates if a
-locally-originated incoming message does not have one. &"Locally-originated"&
-means &"not received over TCP/IP."&
-Otherwise, the primary host name is used.
-Only letters, digits, dot and hyphen are accepted; any other characters are
-replaced by hyphens. If the expansion is forced to fail, or if the result is an
-empty string, the option is ignored.
-
-
-.option message_id_header_text main string&!! unset
-If this variable is set, the string is expanded and used to augment the text of
-the &'Message-id:'& header that Exim creates if a locally-originated incoming
-message does not have one. The text of this header is required by RFC 2822 to
-take the form of an address. By default, Exim uses its internal message id as
-the local part, and the primary host name as the domain. If this option is set,
-it is expanded, and provided the expansion is not forced to fail, and does not
-yield an empty string, the result is inserted into the header immediately
-before the @, separated from the internal message id by a dot. Any characters
-that are illegal in an address are automatically converted into hyphens. This
-means that variables such as &$tod_log$& can be used, because the spaces and
-colons will become hyphens.
-
-
-.option message_logs main boolean true
-.cindex "message logs" "disabling"
-.cindex "log" "message log; disabling"
-If this option is turned off, per-message log files are not created in the
-&_msglog_& spool sub-directory. This reduces the amount of disk I/O required by
-Exim, by reducing the number of files involved in handling a message from a
-minimum of four (header spool file, body spool file, delivery journal, and
-per-message log) to three. The other major I/O activity is Exim's main log,
-which is not affected by this option.
-
-
-.option message_size_limit main string&!! 50M
-.cindex "message" "size limit"
-.cindex "limit" "message size"
-.cindex "size" "of message, limit"
-This option limits the maximum size of message that Exim will process. The
-value is expanded for each incoming connection so, for example, it can be made
-to depend on the IP address of the remote host for messages arriving via
-TCP/IP. After expansion, the value must be a sequence of decimal digits,
-optionally followed by K or M.
-
-&*Note*&: This limit cannot be made to depend on a message's sender or any
-other properties of an individual message, because it has to be advertised in
-the server's response to EHLO. String expansion failure causes a temporary
-error. A value of zero means no limit, but its use is not recommended. See also
-&%bounce_return_size_limit%&.
-
-Incoming SMTP messages are failed with a 552 error if the limit is
-exceeded; locally-generated messages either get a stderr message or a delivery
-failure message to the sender, depending on the &%-oe%& setting. Rejection of
-an oversized message is logged in both the main and the reject logs. See also
-the generic transport option &%message_size_limit%&, which limits the size of
-message that an individual transport can process.
-
-If you use a virus-scanner and set this option to to a value larger than the
-maximum size that your virus-scanner is configured to support, you may get
-failures triggered by large mails.  The right size to configure for the
-virus-scanner depends upon what data is passed and the options in use but it's
-probably safest to just set it to a little larger than this value.  E.g., with a
-default Exim message size of 50M and a default ClamAV StreamMaxLength of 10M,
-some problems may result.
-
-A value of 0 will disable size limit checking; Exim will still advertise the
-SIZE extension in an EHLO response, but without a limit, so as to permit
-SMTP clients to still indicate the message size along with the MAIL verb.
-
-
-.option move_frozen_messages main boolean false
-.cindex "frozen messages" "moving"
-This option, which is available only if Exim has been built with the setting
-.code
-SUPPORT_MOVE_FROZEN_MESSAGES=yes
-.endd
-in &_Local/Makefile_&, causes frozen messages and their message logs to be
-moved from the &_input_& and &_msglog_& directories on the spool to &_Finput_&
-and &_Fmsglog_&, respectively. There is currently no support in Exim or the
-standard utilities for handling such moved messages, and they do not show up in
-lists generated by &%-bp%& or by the Exim monitor.
-
-
-.option mua_wrapper main boolean false
-Setting this option true causes Exim to run in a very restrictive mode in which
-it passes messages synchronously to a smart host. Chapter &<<CHAPnonqueueing>>&
-contains a full description of this facility.
-
-
-
-.option mysql_servers main "string list" unset
-.cindex "MySQL" "server list"
-This option provides a list of MySQL servers and associated connection data, to
-be used in conjunction with &(mysql)& lookups (see section &<<SECID72>>&). The
-option is available only if Exim has been built with MySQL support.
-
-
-.option never_users main "string list&!!" unset
-This option is expanded just once, at the start of Exim's processing. Local
-message deliveries are normally run in processes that are setuid to the
-recipient, and remote deliveries are normally run under Exim's own uid and gid.
-It is usually desirable to prevent any deliveries from running as root, as a
-safety precaution.
-
-When Exim is built, an option called FIXED_NEVER_USERS can be set to a
-list of users that must not be used for local deliveries. This list is fixed in
-the binary and cannot be overridden by the configuration file. By default, it
-contains just the single user name &"root"&. The &%never_users%& runtime option
-can be used to add more users to the fixed list.
-
-If a message is to be delivered as one of the users on the fixed list or the
-&%never_users%& list, an error occurs, and delivery is deferred. A common
-example is
-.code
-never_users = root:daemon:bin
-.endd
-Including root is redundant if it is also on the fixed list, but it does no
-harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)&
-transport driver.
-
-
-.new
-.option notifier_socket main string "$spool_directory/exim_daemon_notify"
-This option gives the name for a unix-domain socket on which the daemon
-listens for work and information-requests.
-Only installations running multiple daemons sharing a spool directory
-should need to modify the default.
-
-The option is expanded before use.
-If the platform supports Linux-style abstract socket names, the result
-is used with a nul byte prefixed.
-Otherwise, it should be a full path name and use a directory accessible
-to Exim.
-
-If the Exim command line uses a &%-oX%& option and does not use &%-oP%&
-then a notifier socket is not created.
-.wen
-
-
-.option openssl_options main "string list" "+no_sslv2 +no_sslv3 +single_dh_use +no_ticket +no_renegotiation"
-.cindex "OpenSSL "compatibility options"
-This option allows an administrator to adjust the SSL options applied
-by OpenSSL to connections.  It is given as a space-separated list of items,
-each one to be +added or -subtracted from the current value.
-
-This option is only available if Exim is built against OpenSSL.  The values
-available for this option vary according to the age of your OpenSSL install.
-The &"all"& value controls a subset of flags which are available, typically
-the bug workaround options.  The &'SSL_CTX_set_options'& man page will
-list the values known on your system and Exim should support all the
-&"bug workaround"& options and many of the &"modifying"& options.  The Exim
-names lose the leading &"SSL_OP_"& and are lower-cased.
-
-Note that adjusting the options can have severe impact upon the security of
-SSL as used by Exim.  It is possible to disable safety checks and shoot
-yourself in the foot in various unpleasant ways.  This option should not be
-adjusted lightly.  An unrecognised item will be detected at startup, by
-invoking Exim with the &%-bV%& flag.
-
-The option affects Exim operating both as a server and as a client.
-
-Historical note: prior to release 4.80, Exim defaulted this value to
-"+dont_insert_empty_fragments", which may still be needed for compatibility
-with some clients, but which lowers security by increasing exposure to
-some now infamous attacks.
-
-Examples:
-.code
-# Make both old MS and old Eudora happy:
-openssl_options = -all +microsoft_big_sslv3_buffer \
-                       +dont_insert_empty_fragments
-
-# Disable older protocol versions:
-openssl_options = +no_sslv2 +no_sslv3
-.endd
-
-Possible options may include:
-.ilist
-&`all`&
-.next
-&`allow_unsafe_legacy_renegotiation`&
-.next
-&`cipher_server_preference`&
-.next
-&`dont_insert_empty_fragments`&
-.next
-&`ephemeral_rsa`&
-.next
-&`legacy_server_connect`&
-.next
-&`microsoft_big_sslv3_buffer`&
-.next
-&`microsoft_sess_id_bug`&
-.next
-&`msie_sslv2_rsa_padding`&
-.next
-&`netscape_challenge_bug`&
-.next
-&`netscape_reuse_cipher_change_bug`&
-.next
-&`no_compression`&
-.next
-&`no_session_resumption_on_renegotiation`&
-.next
-&`no_sslv2`&
-.next
-&`no_sslv3`&
-.next
-&`no_ticket`&
-.next
-&`no_tlsv1`&
-.next
-&`no_tlsv1_1`&
-.next
-&`no_tlsv1_2`&
-.next
-&`safari_ecdhe_ecdsa_bug`&
-.next
-&`single_dh_use`&
-.next
-&`single_ecdh_use`&
-.next
-&`ssleay_080_client_dh_bug`&
-.next
-&`sslref2_reuse_cert_type_bug`&
-.next
-&`tls_block_padding_bug`&
-.next
-&`tls_d5_bug`&
-.next
-&`tls_rollback_bug`&
-.endlist
-
-As an aside, the &`safari_ecdhe_ecdsa_bug`& item is a misnomer and affects
-all clients connecting using the MacOS SecureTransport TLS facility prior
-to MacOS 10.8.4, including email clients.  If you see old MacOS clients failing
-to negotiate TLS then this option value might help, provided that your OpenSSL
-release is new enough to contain this work-around.  This may be a situation
-where you have to upgrade OpenSSL to get buggy clients working.
-
-
-.option oracle_servers main "string list" unset
-.cindex "Oracle" "server list"
-This option provides a list of Oracle servers and associated connection data,
-to be used in conjunction with &(oracle)& lookups (see section &<<SECID72>>&).
-The option is available only if Exim has been built with Oracle support.
-
-
-.option percent_hack_domains main "domain list&!!" unset
-.cindex "&""percent hack""&"
-.cindex "source routing" "in email address"
-.cindex "address" "source-routed"
-The &"percent hack"& is the convention whereby a local part containing a
-percent sign is re-interpreted as a new email address, with the percent
-replaced by @. This is sometimes called &"source routing"&, though that term is
-also applied to RFC 2822 addresses that begin with an @ character. If this
-option is set, Exim implements the percent facility for those domains listed,
-but no others. This happens before an incoming SMTP address is tested against
-an ACL.
-
-&*Warning*&: The &"percent hack"& has often been abused by people who are
-trying to get round relaying restrictions. For this reason, it is best avoided
-if at all possible. Unfortunately, a number of less security-conscious MTAs
-implement it unconditionally. If you are running Exim on a gateway host, and
-routing mail through to internal MTAs without processing the local parts, it is
-a good idea to reject recipient addresses with percent characters in their
-local parts. Exim's default configuration does this.
-
-
-.option perl_at_start main boolean false
-.cindex "Perl"
-This option is available only when Exim is built with an embedded Perl
-interpreter. See chapter &<<CHAPperl>>& for details of its use.
-
-
-.option perl_startup main string unset
-.cindex "Perl"
-This option is available only when Exim is built with an embedded Perl
-interpreter. See chapter &<<CHAPperl>>& for details of its use.
-
-.option perl_taintmode main boolean false
-.cindex "Perl"
-This option enables the taint mode of the embedded Perl interpreter.
-
-
-.option pgsql_servers main "string list" unset
-.cindex "PostgreSQL lookup type" "server list"
-This option provides a list of PostgreSQL servers and associated connection
-data, to be used in conjunction with &(pgsql)& lookups (see section
-&<<SECID72>>&). The option is available only if Exim has been built with
-PostgreSQL support.
-
-
-.option pid_file_path main string&!! "set at compile time"
-.cindex "daemon" "pid file path"
-.cindex "pid file, path for"
-This option sets the name of the file to which the Exim daemon writes its
-process id. The string is expanded, so it can contain, for example, references
-to the host name:
-.code
-pid_file_path = /var/log/$primary_hostname/exim.pid
-.endd
-If no path is set, the pid is written to the file &_exim-daemon.pid_& in Exim's
-spool directory.
-The value set by the option can be overridden by the &%-oP%& command line
-option. A pid file is not written if a &"non-standard"& daemon is run by means
-of the &%-oX%& option, unless a path is explicitly supplied by &%-oP%&.
-
-
-.option pipelining_advertise_hosts main "host list&!!" *
-.cindex "PIPELINING" "suppressing advertising"
-This option can be used to suppress the advertisement of the SMTP
-PIPELINING extension to specific hosts. See also the &*no_pipelining*&
-control in section &<<SECTcontrols>>&. When PIPELINING is not advertised and
-&%smtp_enforce_sync%& is true, an Exim server enforces strict synchronization
-for each SMTP command and response. When PIPELINING is advertised, Exim assumes
-that clients will use it; &"out of order"& commands that are &"expected"& do
-not count as protocol errors (see &%smtp_max_synprot_errors%&).
-
-.option pipelining_connect_advertise_hosts main "host list&!!" *
-.cindex "pipelining" "early connection"
-.cindex "pipelining" PIPE_CONNECT
-If Exim is built with the SUPPORT_PIPE_CONNECT build option
-this option controls which hosts the facility is advertised to
-and from which pipeline early-connection (before MAIL) SMTP
-commands are acceptable.
-When used, the pipelining saves on roundtrip times.
-
-See also the &%hosts_pipe_connect%& smtp transport option.
-
-Currently the option name &"X_PIPE_CONNECT"& is used.
-
-
-.option prdr_enable main boolean false
-.cindex "PRDR" "enabling on server"
-This option can be used to enable the Per-Recipient Data Response extension
-to SMTP, defined by Eric Hall.
-If the option is set, PRDR is advertised by Exim when operating as a server.
-If the client requests PRDR, and more than one recipient, for a message
-an additional ACL is called for each recipient after the message content
-is received.  See section &<<SECTPRDRACL>>&.
-
-.option preserve_message_logs main boolean false
-.cindex "message logs" "preserving"
-If this option is set, message log files are not deleted when messages are
-completed. Instead, they are moved to a sub-directory of the spool directory
-called &_msglog.OLD_&, where they remain available for statistical or debugging
-purposes. This is a dangerous option to set on systems with any appreciable
-volume of mail. Use with care!
-
-
-.option primary_hostname main string "see below"
-.cindex "name" "of local host"
-.cindex "host" "name of local"
-.cindex "local host" "name of"
-.vindex "&$primary_hostname$&"
-This specifies the name of the current host. It is used in the default EHLO or
-HELO command for outgoing SMTP messages (changeable via the &%helo_data%&
-option in the &(smtp)& transport), and as the default for &%qualify_domain%&.
-The value is also used by default in some SMTP response messages from an Exim
-server. This can be changed dynamically by setting &%smtp_active_hostname%&.
-
-If &%primary_hostname%& is not set, Exim calls &[uname()]& to find the host
-name. If this fails, Exim panics and dies. If the name returned by &[uname()]&
-contains only one component, Exim passes it to &[gethostbyname()]& (or
-&[getipnodebyname()]& when available) in order to obtain the fully qualified
-version. The variable &$primary_hostname$& contains the host name, whether set
-explicitly by this option, or defaulted.
-
-
-.option print_topbitchars main boolean false
-.cindex "printing characters"
-.cindex "8-bit characters"
-By default, Exim considers only those characters whose codes lie in the range
-32&--126 to be printing characters. In a number of circumstances (for example,
-when writing log entries) non-printing characters are converted into escape
-sequences, primarily to avoid messing up the layout. If &%print_topbitchars%&
-is set, code values of 128 and above are also considered to be printing
-characters.
-
-This option also affects the header syntax checks performed by the
-&(autoreply)& transport, and whether Exim uses RFC 2047 encoding of
-the user's full name when constructing From: and Sender: addresses (as
-described in section &<<SECTconstr>>&). Setting this option can cause
-Exim to generate eight bit message headers that do not conform to the
-standards.
-
-
-.option process_log_path main string unset
-.cindex "process log path"
-.cindex "log" "process log"
-.cindex "&'exiwhat'&"
-This option sets the name of the file to which an Exim process writes its
-&"process log"& when sent a USR1 signal. This is used by the &'exiwhat'&
-utility script. If this option is unset, the file called &_exim-process.info_&
-in Exim's spool directory is used. The ability to specify the name explicitly
-can be useful in environments where two different Exims are running, using
-different spool directories.
-
-
-.option prod_requires_admin main boolean true
-.cindex "restricting access to features"
-.oindex "&%-M%&"
-.oindex "&%-R%&"
-.oindex "&%-q%&"
-The &%-M%&, &%-R%&, and &%-q%& command-line options require the caller to be an
-admin user unless &%prod_requires_admin%& is set false. See also
-&%queue_list_requires_admin%& and &%commandline_checks_require_admin%&.
-
-
-.option qualify_domain main string "see below"
-.cindex "domain" "for qualifying addresses"
-.cindex "address" "qualification"
-This option specifies the domain name that is added to any envelope sender
-addresses that do not have a domain qualification. It also applies to
-recipient addresses if &%qualify_recipient%& is not set. Unqualified addresses
-are accepted by default only for locally-generated messages. Qualification is
-also applied to addresses in header lines such as &'From:'& and &'To:'& for
-locally-generated messages, unless the &%-bnq%& command line option is used.
-
-Messages from external sources must always contain fully qualified addresses,
-unless the sending host matches &%sender_unqualified_hosts%& or
-&%recipient_unqualified_hosts%& (as appropriate), in which case incoming
-addresses are qualified with &%qualify_domain%& or &%qualify_recipient%& as
-necessary. Internally, Exim always works with fully qualified envelope
-addresses. If &%qualify_domain%& is not set, it defaults to the
-&%primary_hostname%& value.
-
-
-.option qualify_recipient main string "see below"
-This option allows you to specify a different domain for qualifying recipient
-addresses to the one that is used for senders. See &%qualify_domain%& above.
-
-
-
-.option queue_domains main "domain list&!!" unset
-.cindex "domain" "specifying non-immediate delivery"
-.cindex "queueing incoming messages"
-.cindex "message" "queueing certain domains"
-This option lists domains for which immediate delivery is not required.
-A delivery process is started whenever a message is received, but only those
-domains that do not match are processed. All other deliveries wait until the
-next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&.
-
-
-.option queue_list_requires_admin main boolean true
-.cindex "restricting access to features"
-.oindex "&%-bp%&"
-The &%-bp%& command-line option, which lists the messages that are on the
-queue, requires the caller to be an admin user unless
-&%queue_list_requires_admin%& is set false.
-See also &%prod_requires_admin%& and &%commandline_checks_require_admin%&.
-
-
-.option queue_only main boolean false
-.cindex "queueing incoming messages"
-.cindex "message" "queueing unconditionally"
-If &%queue_only%& is set, a delivery process is not automatically started
-whenever a message is received. Instead, the message waits in the queue for the
-next queue run. Even if &%queue_only%& is false, incoming messages may not get
-delivered immediately when certain conditions (such as heavy load) occur.
-
-The &%-odq%& command line has the same effect as &%queue_only%&. The &%-odb%&
-and &%-odi%& command line options override &%queue_only%& unless
-&%queue_only_override%& is set false. See also &%queue_only_file%&,
-&%queue_only_load%&, and &%smtp_accept_queue%&.
-
-
-.option queue_only_file main string unset
-.cindex "queueing incoming messages"
-.cindex "message" "queueing by file existence"
-This option can be set to a colon-separated list of absolute path names, each
-one optionally preceded by &"smtp"&. When Exim is receiving a message,
-it tests for the existence of each listed path using a call to &[stat()]&. For
-each path that exists, the corresponding queueing option is set.
-For paths with no prefix, &%queue_only%& is set; for paths prefixed by
-&"smtp"&, &%queue_smtp_domains%& is set to match all domains. So, for example,
-.code
-queue_only_file = smtp/some/file
-.endd
-causes Exim to behave as if &%queue_smtp_domains%& were set to &"*"& whenever
-&_/some/file_& exists.
-
-
-.option queue_only_load main fixed-point unset
-.cindex "load average"
-.cindex "queueing incoming messages"
-.cindex "message" "queueing by load"
-If the system load average is higher than this value, incoming messages from
-all sources are queued, and no automatic deliveries are started. If this
-happens during local or remote SMTP input, all subsequent messages received on
-the same SMTP connection are queued by default, whatever happens to the load in
-the meantime, but this can be changed by setting &%queue_only_load_latch%&
-false.
-
-Deliveries will subsequently be performed by queue runner processes. This
-option has no effect on ancient operating systems on which Exim cannot
-determine the load average. See also &%deliver_queue_load_max%& and
-&%smtp_load_reserve%&.
-
-
-.option queue_only_load_latch main boolean true
-.cindex "load average" "re-evaluating per message"
-When this option is true (the default), once one message has been queued
-because the load average is higher than the value set by &%queue_only_load%&,
-all subsequent messages received on the same SMTP connection are also queued.
-This is a deliberate choice; even though the load average may fall below the
-threshold, it doesn't seem right to deliver later messages on the same
-connection when not delivering earlier ones. However, there are special
-circumstances such as very long-lived connections from scanning appliances
-where this is not the best strategy. In such cases, &%queue_only_load_latch%&
-should be set false. This causes the value of the load average to be
-re-evaluated for each message.
-
-
-.option queue_only_override main boolean true
-.cindex "queueing incoming messages"
-When this option is true, the &%-od%&&'x'& command line options override the
-setting of &%queue_only%& or &%queue_only_file%& in the configuration file. If
-&%queue_only_override%& is set false, the &%-od%&&'x'& options cannot be used
-to override; they are accepted, but ignored.
-
-
-.option queue_run_in_order main boolean false
-.cindex "queue runner" "processing messages in order"
-If this option is set, queue runs happen in order of message arrival instead of
-in an arbitrary order. For this to happen, a complete list of the entire queue
-must be set up before the deliveries start. When the queue is all held in a
-single directory (the default), a single list is created for both the ordered
-and the non-ordered cases. However, if &%split_spool_directory%& is set, a
-single list is not created when &%queue_run_in_order%& is false. In this case,
-the sub-directories are processed one at a time (in a random order), and this
-avoids setting up one huge list for the whole queue. Thus, setting
-&%queue_run_in_order%& with &%split_spool_directory%& may degrade performance
-when the queue is large, because of the extra work in setting up the single,
-large list. In most situations, &%queue_run_in_order%& should not be set.
-
-
-
-.option queue_run_max main integer&!! 5
-.cindex "queue runner" "maximum number of"
-This controls the maximum number of queue runner processes that an Exim daemon
-can run simultaneously. This does not mean that it starts them all at once,
-but rather that if the maximum number are still running when the time comes to
-start another one, it refrains from starting another one. This can happen with
-very large queues and/or very sluggish deliveries. This option does not,
-however, interlock with other processes, so additional queue runners can be
-started by other means, or by killing and restarting the daemon.
-
-Setting this option to zero does not suppress queue runs; rather, it disables
-the limit, allowing any number of simultaneous queue runner processes to be
-run. If you do not want queue runs to occur, omit the &%-q%&&'xx'& setting on
-the daemon's command line.
-
-.cindex queues named
-.cindex "named queues" "resource limit"
-To set limits for different named queues use
-an expansion depending on the &$queue_name$& variable.
-
-.option queue_smtp_domains main "domain list&!!" unset
-.cindex "queueing incoming messages"
-.cindex "message" "queueing remote deliveries"
-.cindex "first pass routing"
-When this option is set, a delivery process is started whenever a message is
-received, routing is performed, and local deliveries take place.
-However, if any SMTP deliveries are required for domains that match
-&%queue_smtp_domains%&, they are not immediately delivered, but instead the
-message waits in the queue for the next queue run. Since routing of the message
-has taken place, Exim knows to which remote hosts it must be delivered, and so
-when the queue run happens, multiple messages for the same host are delivered
-over a single SMTP connection. The &%-odqs%& command line option causes all
-SMTP deliveries to be queued in this way, and is equivalent to setting
-&%queue_smtp_domains%& to &"*"&. See also &%hold_domains%& and
-&%queue_domains%&.
-
-
-.option receive_timeout main time 0s
-.cindex "timeout" "for non-SMTP input"
-This option sets the timeout for accepting a non-SMTP message, that is, the
-maximum time that Exim waits when reading a message on the standard input. If
-the value is zero, it will wait forever. This setting is overridden by the
-&%-or%& command line option. The timeout for incoming SMTP messages is
-controlled by &%smtp_receive_timeout%&.
-
-.option received_header_text main string&!! "see below"
-.cindex "customizing" "&'Received:'& header"
-.cindex "&'Received:'& header line" "customizing"
-This string defines the contents of the &'Received:'& message header that is
-added to each message, except for the timestamp, which is automatically added
-on at the end (preceded by a semicolon). The string is expanded each time it is
-used. If the expansion yields an empty string, no &'Received:'& header line is
-added to the message. Otherwise, the string should start with the text
-&"Received:"& and conform to the RFC 2822 specification for &'Received:'&
-header lines.
-The default setting is:
-
-.code
-received_header_text = Received: \
-  ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\
-    {${if def:sender_ident \
-      {from ${quote_local_part:$sender_ident} }}\
-        ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
-  by $primary_hostname \
-  ${if def:received_protocol {with $received_protocol }}\
-  ${if def:tls_ver           { ($tls_ver)}}\
-  ${if def:tls_in_cipher_std { tls $tls_in_cipher_std\n\t}}\
-  (Exim $version_number)\n\t\
-  ${if def:sender_address \
-  {(envelope-from <$sender_address>)\n\t}}\
-  id $message_exim_id\
-  ${if def:received_for {\n\tfor $received_for}}
-.endd
-
-The reference to the TLS cipher is omitted when Exim is built without TLS
-support. The use of conditional expansions ensures that this works for both
-locally generated messages and messages received from remote hosts, giving
-header lines such as the following:
-.code
-Received: from scrooge.carol.example ([192.168.12.25] ident=root)
-by marley.carol.example with esmtp (Exim 4.00)
-(envelope-from <bob@carol.example>)
-id 16IOWa-00019l-00
-for chas@dickens.example; Tue, 25 Dec 2001 14:43:44 +0000
-Received: by scrooge.carol.example with local (Exim 4.00)
-id 16IOWW-000083-00; Tue, 25 Dec 2001 14:43:41 +0000
-.endd
-Until the body of the message has been received, the timestamp is the time when
-the message started to be received. Once the body has arrived, and all policy
-checks have taken place, the timestamp is updated to the time at which the
-message was accepted.
-
-
-.option received_headers_max main integer 30
-.cindex "loop" "prevention"
-.cindex "mail loop prevention"
-.cindex "&'Received:'& header line" "counting"
-When a message is to be delivered, the number of &'Received:'& headers is
-counted, and if it is greater than this parameter, a mail loop is assumed to
-have occurred, the delivery is abandoned, and an error message is generated.
-This applies to both local and remote deliveries.
-
-
-.option recipient_unqualified_hosts main "host list&!!" unset
-.cindex "unqualified addresses"
-.cindex "host" "unqualified addresses from"
-This option lists those hosts from which Exim is prepared to accept unqualified
-recipient addresses in message envelopes. The addresses are made fully
-qualified by the addition of the &%qualify_recipient%& value. This option also
-affects message header lines. Exim does not reject unqualified recipient
-addresses in headers, but it qualifies them only if the message came from a
-host that matches &%recipient_unqualified_hosts%&,
-or if the message was submitted locally (not using TCP/IP), and the &%-bnq%&
-option was not set.
-
-
-.option recipients_max main integer 0
-.cindex "limit" "number of recipients"
-.cindex "recipient" "maximum number"
-If this option is set greater than zero, it specifies the maximum number of
-original recipients for any message. Additional recipients that are generated
-by aliasing or forwarding do not count. SMTP messages get a 452 response for
-all recipients over the limit; earlier recipients are delivered as normal.
-Non-SMTP messages with too many recipients are failed, and no deliveries are
-done.
-
-.cindex "RCPT" "maximum number of incoming"
-&*Note*&: The RFCs specify that an SMTP server should accept at least 100
-RCPT commands in a single message.
-
-
-.option recipients_max_reject main boolean false
-If this option is set true, Exim rejects SMTP messages containing too many
-recipients by giving 552 errors to the surplus RCPT commands, and a 554
-error to the eventual DATA command. Otherwise (the default) it gives a 452
-error to the surplus RCPT commands and accepts the message on behalf of the
-initial set of recipients. The remote server should then re-send the message
-for the remaining recipients at a later time.
-
-
-.option remote_max_parallel main integer 2
-.cindex "delivery" "parallelism for remote"
-This option controls parallel delivery of one message to a number of remote
-hosts. If the value is less than 2, parallel delivery is disabled, and Exim
-does all the remote deliveries for a message one by one. Otherwise, if a single
-message has to be delivered to more than one remote host, or if several copies
-have to be sent to the same remote host, up to &%remote_max_parallel%&
-deliveries are done simultaneously. If more than &%remote_max_parallel%&
-deliveries are required, the maximum number of processes are started, and as
-each one finishes, another is begun. The order of starting processes is the
-same as if sequential delivery were being done, and can be controlled by the
-&%remote_sort_domains%& option. If parallel delivery takes place while running
-with debugging turned on, the debugging output from each delivery process is
-tagged with its process id.
-
-This option controls only the maximum number of parallel deliveries for one
-message in one Exim delivery process. Because Exim has no central queue
-manager, there is no way of controlling the total number of simultaneous
-deliveries if the configuration allows a delivery attempt as soon as a message
-is received.
-
-.cindex "number of deliveries"
-.cindex "delivery" "maximum number of"
-If you want to control the total number of deliveries on the system, you
-need to set the &%queue_only%& option. This ensures that all incoming messages
-are added to the queue without starting a delivery process. Then set up an Exim
-daemon to start queue runner processes at appropriate intervals (probably
-fairly often, for example, every minute), and limit the total number of queue
-runners by setting the &%queue_run_max%& parameter. Because each queue runner
-delivers only one message at a time, the maximum number of deliveries that can
-then take place at once is &%queue_run_max%& multiplied by
-&%remote_max_parallel%&.
-
-If it is purely remote deliveries you want to control, use
-&%queue_smtp_domains%& instead of &%queue_only%&. This has the added benefit of
-doing the SMTP routing before queueing, so that several messages for the same
-host will eventually get delivered down the same connection.
-
-
-.option remote_sort_domains main "domain list&!!" unset
-.cindex "sorting remote deliveries"
-.cindex "delivery" "sorting remote"
-When there are a number of remote deliveries for a message, they are sorted by
-domain into the order given by this list. For example,
-.code
-remote_sort_domains = *.cam.ac.uk:*.uk
-.endd
-would attempt to deliver to all addresses in the &'cam.ac.uk'& domain first,
-then to those in the &%uk%& domain, then to any others.
-
-
-.option retry_data_expire main time 7d
-.cindex "hints database" "data expiry"
-This option sets a &"use before"& time on retry information in Exim's hints
-database. Any older retry data is ignored. This means that, for example, once a
-host has not been tried for 7 days, Exim behaves as if it has no knowledge of
-past failures.
-
-
-.option retry_interval_max main time 24h
-.cindex "retry" "limit on interval"
-.cindex "limit" "on retry interval"
-Chapter &<<CHAPretry>>& describes Exim's mechanisms for controlling the
-intervals between delivery attempts for messages that cannot be delivered
-straight away. This option sets an overall limit to the length of time between
-retries. It cannot be set greater than 24 hours; any attempt to do so forces
-the default value.
-
-
-.option return_path_remove main boolean true
-.cindex "&'Return-path:'& header line" "removing"
-RFC 2821, section 4.4, states that an SMTP server must insert a
-&'Return-path:'& header line into a message when it makes a &"final delivery"&.
-The &'Return-path:'& header preserves the sender address as received in the
-MAIL command. This description implies that this header should not be present
-in an incoming message. If &%return_path_remove%& is true, any existing
-&'Return-path:'& headers are removed from messages at the time they are
-received. Exim's transports have options for adding &'Return-path:'& headers at
-the time of delivery. They are normally used only for final local deliveries.
-
-
-.option return_size_limit main integer 100K
-This option is an obsolete synonym for &%bounce_return_size_limit%&.
-
-
-.option rfc1413_hosts main "host list&!!" @[]
-.cindex "RFC 1413"
-.cindex "host" "for RFC 1413 calls"
-RFC 1413 identification calls are made to any client host which matches
-an item in the list.
-The default value specifies just this host, being any local interface
-for the system.
-
-.option rfc1413_query_timeout main time 0s
-.cindex "RFC 1413" "query timeout"
-.cindex "timeout" "for RFC 1413 call"
-This sets the timeout on RFC 1413 identification calls. If it is set to zero,
-no RFC 1413 calls are ever made.
-
-
-.option sender_unqualified_hosts main "host list&!!" unset
-.cindex "unqualified addresses"
-.cindex "host" "unqualified addresses from"
-This option lists those hosts from which Exim is prepared to accept unqualified
-sender addresses. The addresses are made fully qualified by the addition of
-&%qualify_domain%&. This option also affects message header lines. Exim does
-not reject unqualified addresses in headers that contain sender addresses, but
-it qualifies them only if the message came from a host that matches
-&%sender_unqualified_hosts%&, or if the message was submitted locally (not
-using TCP/IP), and the &%-bnq%& option was not set.
-
-
-.option slow_lookup_log main integer 0
-.cindex "logging" "slow lookups"
-.cindex "dns" "logging slow lookups"
-This option controls logging of slow lookups.
-If the value is nonzero it is taken as a number of milliseconds
-and lookups taking longer than this are logged.
-Currently this applies only to DNS lookups.
-
-
-
-.option smtp_accept_keepalive main boolean true
-.cindex "keepalive" "on incoming connection"
-This option controls the setting of the SO_KEEPALIVE option on incoming
-TCP/IP socket connections. When set, it causes the kernel to probe idle
-connections periodically, by sending packets with &"old"& sequence numbers. The
-other end of the connection should send an acknowledgment if the connection is
-still okay or a reset if the connection has been aborted. The reason for doing
-this is that it has the beneficial effect of freeing up certain types of
-connection that can get stuck when the remote host is disconnected without
-tidying up the TCP/IP call properly. The keepalive mechanism takes several
-hours to detect unreachable hosts.
-
-
-
-.option smtp_accept_max main integer 20
-.cindex "limit" "incoming SMTP connections"
-.cindex "SMTP" "incoming connection count"
-.cindex "inetd"
-This option specifies the maximum number of simultaneous incoming SMTP calls
-that Exim will accept. It applies only to the listening daemon; there is no
-control (in Exim) when incoming SMTP is being handled by &'inetd'&. If the
-value is set to zero, no limit is applied. However, it is required to be
-non-zero if either &%smtp_accept_max_per_host%& or &%smtp_accept_queue%& is
-set. See also &%smtp_accept_reserve%& and &%smtp_load_reserve%&.
-
-A new SMTP connection is immediately rejected if the &%smtp_accept_max%& limit
-has been reached. If not, Exim first checks &%smtp_accept_max_per_host%&. If
-that limit has not been reached for the client host, &%smtp_accept_reserve%&
-and &%smtp_load_reserve%& are then checked before accepting the connection.
-
-
-.option smtp_accept_max_nonmail main integer 10
-.cindex "limit" "non-mail SMTP commands"
-.cindex "SMTP" "limiting non-mail commands"
-Exim counts the number of &"non-mail"& commands in an SMTP session, and drops
-the connection if there are too many. This option defines &"too many"&. The
-check catches some denial-of-service attacks, repeated failing AUTHs, or a mad
-client looping sending EHLO, for example. The check is applied only if the
-client host matches &%smtp_accept_max_nonmail_hosts%&.
-
-When a new message is expected, one occurrence of RSET is not counted. This
-allows a client to send one RSET between messages (this is not necessary,
-but some clients do it). Exim also allows one uncounted occurrence of HELO
-or EHLO, and one occurrence of STARTTLS between messages. After
-starting up a TLS session, another EHLO is expected, and so it too is not
-counted. The first occurrence of AUTH in a connection, or immediately
-following STARTTLS is not counted. Otherwise, all commands other than
-MAIL, RCPT, DATA, and QUIT are counted.
-
-
-.option smtp_accept_max_nonmail_hosts main "host list&!!" *
-You can control which hosts are subject to the &%smtp_accept_max_nonmail%&
-check by setting this option. The default value makes it apply to all hosts. By
-changing the value, you can exclude any badly-behaved hosts that you have to
-live with.
-
-
-. Allow this long option name to split; give it unsplit as a fifth argument
-. for the automatic .oindex that is generated by .option.
-. We insert " &~&~" which is both pretty nasty visually and results in
-. non-searchable text.  HowItWorks.txt mentions an option for inserting
-. zero-width-space, which would be nicer visually and results in (at least)
-. html that Firefox will split on when it's forced to reflow (rather than
-. inserting a horizontal scrollbar).  However, the text is still not
-. searchable.  NM changed this occurrence for bug 1197 to no longer allow
-. the option name to split.
-
-.option "smtp_accept_max_per_connection" main integer 1000 &&&
-         smtp_accept_max_per_connection
-.cindex "SMTP" "limiting incoming message count"
-.cindex "limit" "messages per SMTP connection"
-The value of this option limits the number of MAIL commands that Exim is
-prepared to accept over a single SMTP connection, whether or not each command
-results in the transfer of a message. After the limit is reached, a 421
-response is given to subsequent MAIL commands. This limit is a safety
-precaution against a client that goes mad (incidents of this type have been
-seen).
-
-
-.option smtp_accept_max_per_host main string&!! unset
-.cindex "limit" "SMTP connections from one host"
-.cindex "host" "limiting SMTP connections from"
-This option restricts the number of simultaneous IP connections from a single
-host (strictly, from a single IP address) to the Exim daemon. The option is
-expanded, to enable different limits to be applied to different hosts by
-reference to &$sender_host_address$&. Once the limit is reached, additional
-connection attempts from the same host are rejected with error code 421. This
-is entirely independent of &%smtp_accept_reserve%&. The option's default value
-of zero imposes no limit. If this option is set greater than zero, it is
-required that &%smtp_accept_max%& be non-zero.
-
-&*Warning*&: When setting this option you should not use any expansion
-constructions that take an appreciable amount of time. The expansion and test
-happen in the main daemon loop, in order to reject additional connections
-without forking additional processes (otherwise a denial-of-service attack
-could cause a vast number or processes to be created). While the daemon is
-doing this processing, it cannot accept any other incoming connections.
-
-
-
-.option smtp_accept_queue main integer 0
-.cindex "SMTP" "incoming connection count"
-.cindex "queueing incoming messages"
-.cindex "message" "queueing by SMTP connection count"
-If the number of simultaneous incoming SMTP connections being handled via the
-listening daemon exceeds this value, messages received by SMTP are just placed
-in the queue; no delivery processes are started automatically. The count is
-fixed at the start of an SMTP connection. It cannot be updated in the
-subprocess that receives messages, and so the queueing or not queueing applies
-to all messages received in the same connection.
-
-A value of zero implies no limit, and clearly any non-zero value is useful only
-if it is less than the &%smtp_accept_max%& value (unless that is zero). See
-also &%queue_only%&, &%queue_only_load%&, &%queue_smtp_domains%&, and the
-various &%-od%&&'x'& command line options.
-
-
-. See the comment on smtp_accept_max_per_connection
-
-.option "smtp_accept_queue_per_connection" main integer 10 &&&
-         smtp_accept_queue_per_connection
-.cindex "queueing incoming messages"
-.cindex "message" "queueing by message count"
-This option limits the number of delivery processes that Exim starts
-automatically when receiving messages via SMTP, whether via the daemon or by
-the use of &%-bs%& or &%-bS%&. If the value of the option is greater than zero,
-and the number of messages received in a single SMTP session exceeds this
-number, subsequent messages are placed in the queue, but no delivery processes
-are started. This helps to limit the number of Exim processes when a server
-restarts after downtime and there is a lot of mail waiting for it on other
-systems. On large systems, the default should probably be increased, and on
-dial-in client systems it should probably be set to zero (that is, disabled).
-
-
-.option smtp_accept_reserve main integer 0
-.cindex "SMTP" "incoming call count"
-.cindex "host" "reserved"
-When &%smtp_accept_max%& is set greater than zero, this option specifies a
-number of SMTP connections that are reserved for connections from the hosts
-that are specified in &%smtp_reserve_hosts%&. The value set in
-&%smtp_accept_max%& includes this reserve pool. The specified hosts are not
-restricted to this number of connections; the option specifies a minimum number
-of connection slots for them, not a maximum. It is a guarantee that this group
-of hosts can always get at least &%smtp_accept_reserve%& connections. However,
-the limit specified by &%smtp_accept_max_per_host%& is still applied to each
-individual host.
-
-For example, if &%smtp_accept_max%& is set to 50 and &%smtp_accept_reserve%& is
-set to 5, once there are 45 active connections (from any hosts), new
-connections are accepted only from hosts listed in &%smtp_reserve_hosts%&,
-provided the other criteria for acceptance are met.
-
-
-.option smtp_active_hostname main string&!! unset
-.cindex "host" "name in SMTP responses"
-.cindex "SMTP" "host name in responses"
-.vindex "&$primary_hostname$&"
-This option is provided for multi-homed servers that want to masquerade as
-several different hosts. At the start of an incoming SMTP connection, its value
-is expanded and used instead of the value of &$primary_hostname$& in SMTP
-responses. For example, it is used as domain name in the response to an
-incoming HELO or EHLO command.
-
-.vindex "&$smtp_active_hostname$&"
-The active hostname is placed in the &$smtp_active_hostname$& variable, which
-is saved with any messages that are received. It is therefore available for use
-in routers and transports when the message is later delivered.
-
-If this option is unset, or if its expansion is forced to fail, or if the
-expansion results in an empty string, the value of &$primary_hostname$& is
-used. Other expansion failures cause a message to be written to the main and
-panic logs, and the SMTP command receives a temporary error. Typically, the
-value of &%smtp_active_hostname%& depends on the incoming interface address.
-For example:
-.code
-smtp_active_hostname = ${if eq{$received_ip_address}{10.0.0.1}\
-  {cox.mydomain}{box.mydomain}}
-.endd
-
-Although &$smtp_active_hostname$& is primarily concerned with incoming
-messages, it is also used as the default for HELO commands in callout
-verification if there is no remote transport from which to obtain a
-&%helo_data%& value.
-
-.option smtp_banner main string&!! "see below"
-.cindex "SMTP" "welcome banner"
-.cindex "banner for SMTP"
-.cindex "welcome banner for SMTP"
-.cindex "customizing" "SMTP banner"
-This string, which is expanded every time it is used, is output as the initial
-positive response to an SMTP connection. The default setting is:
-.code
-smtp_banner = $smtp_active_hostname ESMTP Exim \
-  $version_number $tod_full
-.endd
-Failure to expand the string causes a panic error. If you want to create a
-multiline response to the initial SMTP connection, use &"\n"& in the string at
-appropriate points, but not at the end. Note that the 220 code is not included
-in this string. Exim adds it automatically (several times in the case of a
-multiline response).
-
-
-.option smtp_check_spool_space main boolean true
-.cindex "checking disk space"
-.cindex "disk space, checking"
-.cindex "spool directory" "checking space"
-When this option is set, if an incoming SMTP session encounters the SIZE
-option on a MAIL command, it checks that there is enough space in the
-spool directory's partition to accept a message of that size, while still
-leaving free the amount specified by &%check_spool_space%& (even if that value
-is zero). If there isn't enough space, a temporary error code is returned.
-
-
-.option smtp_connect_backlog main integer 20
-.cindex "connection backlog"
-.cindex "SMTP" "connection backlog"
-.cindex "backlog of connections"
-This option specifies a maximum number of waiting SMTP connections. Exim passes
-this value to the TCP/IP system when it sets up its listener. Once this number
-of connections are waiting for the daemon's attention, subsequent connection
-attempts are refused at the TCP/IP level. At least, that is what the manuals
-say; in some circumstances such connection attempts have been observed to time
-out instead. For large systems it is probably a good idea to increase the
-value (to 50, say). It also gives some protection against denial-of-service
-attacks by SYN flooding.
-
-
-.option smtp_enforce_sync main boolean true
-.cindex "SMTP" "synchronization checking"
-.cindex "synchronization checking in SMTP"
-The SMTP protocol specification requires the client to wait for a response from
-the server at certain points in the dialogue. Without PIPELINING these
-synchronization points are after every command; with PIPELINING they are
-fewer, but they still exist.
-
-Some spamming sites send out a complete set of SMTP commands without waiting
-for any response. Exim protects against this by rejecting a message if the
-client has sent further input when it should not have. The error response &"554
-SMTP synchronization error"& is sent, and the connection is dropped. Testing
-for this error cannot be perfect because of transmission delays (unexpected
-input may be on its way but not yet received when Exim checks). However, it
-does detect many instances.
-
-The check can be globally disabled by setting &%smtp_enforce_sync%& false.
-If you want to disable the check selectively (for example, only for certain
-hosts), you can do so by an appropriate use of a &%control%& modifier in an ACL
-(see section &<<SECTcontrols>>&). See also &%pipelining_advertise_hosts%&.
-
-
-
-.option smtp_etrn_command main string&!! unset
-.cindex "ETRN" "command to be run"
-.vindex "&$domain$&"
-If this option is set, the given command is run whenever an SMTP ETRN
-command is received from a host that is permitted to issue such commands (see
-chapter &<<CHAPACL>>&). The string is split up into separate arguments which
-are independently expanded. The expansion variable &$domain$& is set to the
-argument of the ETRN command, and no syntax checking is done on it. For
-example:
-.code
-smtp_etrn_command = /etc/etrn_command $domain \
-                    $sender_host_address
-.endd
-.new
-If the option is not set, the argument for the ETRN command must
-be a &'#'& followed by an address string.
-In this case an &'exim -R <string>'& command is used;
-if the ETRN ACL has set up a named-queue then &'-MCG <queue>'& is appended.
-.wen
-
-A new process is created to run the command, but Exim does not wait for it to
-complete. Consequently, its status cannot be checked. If the command cannot be
-run, a line is written to the panic log, but the ETRN caller still receives
-a 250 success response. Exim is normally running under its own uid when
-receiving SMTP, so it is not possible for it to change the uid before running
-the command.
-
-
-.option smtp_etrn_serialize main boolean true
-.cindex "ETRN" "serializing"
-When this option is set, it prevents the simultaneous execution of more than
-one identical command as a result of ETRN in an SMTP connection. See
-section &<<SECTETRN>>& for details.
-
-
-.option smtp_load_reserve main fixed-point unset
-.cindex "load average"
-If the system load average ever gets higher than this, incoming SMTP calls are
-accepted only from those hosts that match an entry in &%smtp_reserve_hosts%&.
-If &%smtp_reserve_hosts%& is not set, no incoming SMTP calls are accepted when
-the load is over the limit. The option has no effect on ancient operating
-systems on which Exim cannot determine the load average. See also
-&%deliver_queue_load_max%& and &%queue_only_load%&.
-
-
-
-.option smtp_max_synprot_errors main integer 3
-.cindex "SMTP" "limiting syntax and protocol errors"
-.cindex "limit" "SMTP syntax and protocol errors"
-Exim rejects SMTP commands that contain syntax or protocol errors. In
-particular, a syntactically invalid email address, as in this command:
-.code
-RCPT TO:<abc xyz@a.b.c>
-.endd
-causes immediate rejection of the command, before any other tests are done.
-(The ACL cannot be run if there is no valid address to set up for it.) An
-example of a protocol error is receiving RCPT before MAIL. If there are
-too many syntax or protocol errors in one SMTP session, the connection is
-dropped. The limit is set by this option.
-
-.cindex "PIPELINING" "expected errors"
-When the PIPELINING extension to SMTP is in use, some protocol errors are
-&"expected"&, for instance, a RCPT command after a rejected MAIL command.
-Exim assumes that PIPELINING will be used if it advertises it (see
-&%pipelining_advertise_hosts%&), and in this situation, &"expected"& errors do
-not count towards the limit.
-
-
-
-.option smtp_max_unknown_commands main integer 3
-.cindex "SMTP" "limiting unknown commands"
-.cindex "limit" "unknown SMTP commands"
-If there are too many unrecognized commands in an incoming SMTP session, an
-Exim server drops the connection. This is a defence against some kinds of abuse
-that subvert web
-clients
-into making connections to SMTP ports; in these circumstances, a number of
-non-SMTP command lines are sent first.
-
-
-
-.option smtp_ratelimit_hosts main "host list&!!" unset
-.cindex "SMTP" "rate limiting"
-.cindex "limit" "rate of message arrival"
-.cindex "RCPT" "rate limiting"
-Some sites find it helpful to be able to limit the rate at which certain hosts
-can send them messages, and the rate at which an individual message can specify
-recipients.
-
-Exim has two rate-limiting facilities. This section describes the older
-facility, which can limit rates within a single connection. The newer
-&%ratelimit%& ACL condition can limit rates across all connections. See section
-&<<SECTratelimiting>>& for details of the newer facility.
-
-When a host matches &%smtp_ratelimit_hosts%&, the values of
-&%smtp_ratelimit_mail%& and &%smtp_ratelimit_rcpt%& are used to control the
-rate of acceptance of MAIL and RCPT commands in a single SMTP session,
-respectively. Each option, if set, must contain a set of four comma-separated
-values:
-
-.ilist
-A threshold, before which there is no rate limiting.
-.next
-An initial time delay. Unlike other times in Exim, numbers with decimal
-fractional parts are allowed here.
-.next
-A factor by which to increase the delay each time.
-.next
-A maximum value for the delay. This should normally be less than 5 minutes,
-because after that time, the client is liable to timeout the SMTP command.
-.endlist
-
-For example, these settings have been used successfully at the site which
-first suggested this feature, for controlling mail from their customers:
-.code
-smtp_ratelimit_mail = 2,0.5s,1.05,4m
-smtp_ratelimit_rcpt = 4,0.25s,1.015,4m
-.endd
-The first setting specifies delays that are applied to MAIL commands after
-two have been received over a single connection. The initial delay is 0.5
-seconds, increasing by a factor of 1.05 each time. The second setting applies
-delays to RCPT commands when more than four occur in a single message.
-
-
-.option smtp_ratelimit_mail main string unset
-See &%smtp_ratelimit_hosts%& above.
-
-
-.option smtp_ratelimit_rcpt main string unset
-See &%smtp_ratelimit_hosts%& above.
-
-
-.option smtp_receive_timeout main time&!! 5m
-.cindex "timeout" "for SMTP input"
-.cindex "SMTP" "input timeout"
-This sets a timeout value for SMTP reception. It applies to all forms of SMTP
-input, including batch SMTP. If a line of input (either an SMTP command or a
-data line) is not received within this time, the SMTP connection is dropped and
-the message is abandoned.
-A line is written to the log containing one of the following messages:
-.code
-SMTP command timeout on connection from...
-SMTP data timeout on connection from...
-.endd
-The former means that Exim was expecting to read an SMTP command; the latter
-means that it was in the DATA phase, reading the contents of a message.
-
-If the first character of the option is a &"$"& the option is
-expanded before use and may depend on
-&$sender_host_name$&, &$sender_host_address$& and &$sender_host_port$&.
-
-
-.oindex "&%-os%&"
-The value set by this option can be overridden by the
-&%-os%& command-line option. A setting of zero time disables the timeout, but
-this should never be used for SMTP over TCP/IP. (It can be useful in some cases
-of local input using &%-bs%& or &%-bS%&.) For non-SMTP input, the reception
-timeout is controlled by &%receive_timeout%& and &%-or%&.
-
-
-.option smtp_reserve_hosts main "host list&!!" unset
-This option defines hosts for which SMTP connections are reserved; see
-&%smtp_accept_reserve%& and &%smtp_load_reserve%& above.
-
-
-.option smtp_return_error_details main boolean false
-.cindex "SMTP" "details policy failures"
-.cindex "policy control" "rejection, returning details"
-In the default state, Exim uses bland messages such as
-&"Administrative prohibition"& when it rejects SMTP commands for policy
-reasons. Many sysadmins like this because it gives away little information
-to spammers. However, some other sysadmins who are applying strict checking
-policies want to give out much fuller information about failures. Setting
-&%smtp_return_error_details%& true causes Exim to be more forthcoming. For
-example, instead of &"Administrative prohibition"&, it might give:
-.code
-550-Rejected after DATA: '>' missing at end of address:
-550 failing address in "From" header is: <user@dom.ain
-.endd
-
-
-.option smtputf8_advertise_hosts main "host list&!!" *
-.cindex "SMTPUTF8" "advertising"
-When Exim is built with support for internationalised mail names,
-the availability thereof is advertised in
-response to EHLO only to those client hosts that match this option. See
-chapter &<<CHAPi18n>>& for details of Exim's support for internationalisation.
-
-
-.option spamd_address main string "127.0.0.1 783"
-This option is available when Exim is compiled with the content-scanning
-extension. It specifies how Exim connects to SpamAssassin's &%spamd%& daemon.
-See section &<<SECTscanspamass>>& for more details.
-
-
-
-.option spf_guess main string "v=spf1 a/24 mx/24 ptr ?all"
-This option is available when Exim is compiled with SPF support.
-See section &<<SECSPF>>& for more details.
-
-
-
-.option split_spool_directory main boolean false
-.cindex "multiple spool directories"
-.cindex "spool directory" "split"
-.cindex "directories, multiple"
-If this option is set, it causes Exim to split its input directory into 62
-subdirectories, each with a single alphanumeric character as its name. The
-sixth character of the message id is used to allocate messages to
-subdirectories; this is the least significant base-62 digit of the time of
-arrival of the message.
-
-Splitting up the spool in this way may provide better performance on systems
-where there are long mail queues, by reducing the number of files in any one
-directory. The msglog directory is also split up in a similar way to the input
-directory; however, if &%preserve_message_logs%& is set, all old msglog files
-are still placed in the single directory &_msglog.OLD_&.
-
-It is not necessary to take any special action for existing messages when
-changing &%split_spool_directory%&. Exim notices messages that are in the
-&"wrong"& place, and continues to process them. If the option is turned off
-after a period of being on, the subdirectories will eventually empty and be
-automatically deleted.
-
-When &%split_spool_directory%& is set, the behaviour of queue runner processes
-changes. Instead of creating a list of all messages in the queue, and then
-trying to deliver each one, in turn, it constructs a list of those in one
-sub-directory and tries to deliver them, before moving on to the next
-sub-directory. The sub-directories are processed in a random order. This
-spreads out the scanning of the input directories, and uses less memory. It is
-particularly beneficial when there are lots of messages in the queue. However,
-if &%queue_run_in_order%& is set, none of this new processing happens. The
-entire queue has to be scanned and sorted before any deliveries can start.
-
-
-.option spool_directory main string&!! "set at compile time"
-.cindex "spool directory" "path to"
-This defines the directory in which Exim keeps its spool, that is, the messages
-it is waiting to deliver. The default value is taken from the compile-time
-configuration setting, if there is one. If not, this option must be set. The
-string is expanded, so it can contain, for example, a reference to
-&$primary_hostname$&.
-
-If the spool directory name is fixed on your installation, it is recommended
-that you set it at build time rather than from this option, particularly if the
-log files are being written to the spool directory (see &%log_file_path%&).
-Otherwise log files cannot be used for errors that are detected early on, such
-as failures in the configuration file.
-
-By using this option to override the compiled-in path, it is possible to run
-tests of Exim without using the standard spool.
-
-.option spool_wireformat main boolean false
-.cindex "spool directory" "file formats"
-If this option is set, Exim may for some messages use an alternative format
-for data-files in the spool which matches the wire format.
-Doing this permits more efficient message reception and transmission.
-Currently it is only done for messages received using the ESMTP CHUNKING
-option.
-
-The following variables will not have useful values:
-.code
-$max_received_linelength
-$body_linecount
-$body_zerocount
-.endd
-
-Users of the local_scan() API (see &<<CHAPlocalscan>>&),
-and any external programs which are passed a reference to a message data file
-(except via the &"regex"&, &"malware"& or &"spam"&) ACL conditions)
-will need to be aware of the different formats potentially available.
-
-Using any of the ACL conditions noted will negate the reception benefit
-(as a Unix-mbox-format file is constructed for them).
-The transmission benefit is maintained.
-
-.option sqlite_lock_timeout main time 5s
-.cindex "sqlite lookup type" "lock timeout"
-This option controls the timeout that the &(sqlite)& lookup uses when trying to
-access an SQLite database. See section &<<SECTsqlite>>& for more details.
-
-.option strict_acl_vars main boolean false
-.cindex "&ACL;" "variables, handling unset"
-This option controls what happens if a syntactically valid but undefined ACL
-variable is referenced. If it is false (the default), an empty string
-is substituted; if it is true, an error is generated. See section
-&<<SECTaclvariables>>& for details of ACL variables.
-
-.option strip_excess_angle_brackets main boolean false
-.cindex "angle brackets, excess"
-If this option is set, redundant pairs of angle brackets round &"route-addr"&
-items in addresses are stripped. For example, &'<<xxx@a.b.c.d>>'& is
-treated as &'<xxx@a.b.c.d>'&. If this is in the envelope and the message is
-passed on to another MTA, the excess angle brackets are not passed on. If this
-option is not set, multiple pairs of angle brackets cause a syntax error.
-
-
-.option strip_trailing_dot main boolean false
-.cindex "trailing dot on domain"
-.cindex "dot" "trailing on domain"
-If this option is set, a trailing dot at the end of a domain in an address is
-ignored. If this is in the envelope and the message is passed on to another
-MTA, the dot is not passed on. If this option is not set, a dot at the end of a
-domain causes a syntax error.
-However, addresses in header lines are checked only when an ACL requests header
-syntax checking.
-
-
-.option syslog_duplication main boolean true
-.cindex "syslog" "duplicate log lines; suppressing"
-When Exim is logging to syslog, it writes the log lines for its three
-separate logs at different syslog priorities so that they can in principle
-be separated on the logging hosts. Some installations do not require this
-separation, and in those cases, the duplication of certain log lines is a
-nuisance. If &%syslog_duplication%& is set false, only one copy of any
-particular log line is written to syslog. For lines that normally go to
-both the main log and the reject log, the reject log version (possibly
-containing message header lines) is written, at LOG_NOTICE priority.
-Lines that normally go to both the main and the panic log are written at
-the LOG_ALERT priority.
-
-
-.option syslog_facility main string unset
-.cindex "syslog" "facility; setting"
-This option sets the syslog &"facility"& name, used when Exim is logging to
-syslog. The value must be one of the strings &"mail"&, &"user"&, &"news"&,
-&"uucp"&, &"daemon"&, or &"local&'x'&"& where &'x'& is a digit between 0 and 7.
-If this option is unset, &"mail"& is used. See chapter &<<CHAPlog>>& for
-details of Exim's logging.
-
-
-.option syslog_pid main boolean true
-.cindex "syslog" "pid"
-If &%syslog_pid%& is set false, the PID on Exim's log lines are
-omitted when these lines are sent to syslog. (Syslog normally prefixes
-the log lines with the PID of the logging process automatically.) You need
-to enable the &`+pid`& log selector item, if you want Exim to write it's PID
-into the logs.) See chapter &<<CHAPlog>>& for details of Exim's logging.
-
-
-
-.option syslog_processname main string &`exim`&
-.cindex "syslog" "process name; setting"
-This option sets the syslog &"ident"& name, used when Exim is logging to
-syslog. The value must be no longer than 32 characters. See chapter
-&<<CHAPlog>>& for details of Exim's logging.
-
-
-
-.option syslog_timestamp main boolean true
-.cindex "syslog" "timestamps"
-If &%syslog_timestamp%& is set false, the timestamps on Exim's log lines are
-omitted when these lines are sent to syslog. See chapter &<<CHAPlog>>& for
-details of Exim's logging.
-
-
-.option system_filter main string&!! unset
-.cindex "filter" "system filter"
-.cindex "system filter" "specifying"
-.cindex "Sieve filter" "not available for system filter"
-This option specifies an Exim filter file that is applied to all messages at
-the start of each delivery attempt, before any routing is done. System filters
-must be Exim filters; they cannot be Sieve filters. If the system filter
-generates any deliveries to files or pipes, or any new mail messages, the
-appropriate &%system_filter_..._transport%& option(s) must be set, to define
-which transports are to be used. Details of this facility are given in chapter
-&<<CHAPsystemfilter>>&.
-A forced expansion failure results in no filter operation.
-
-
-.option system_filter_directory_transport main string&!! unset
-.vindex "&$address_file$&"
-This sets the name of the transport driver that is to be used when the
-&%save%& command in a system message filter specifies a path ending in &"/"&,
-implying delivery of each message into a separate file in some directory.
-During the delivery, the variable &$address_file$& contains the path name.
-
-
-.option system_filter_file_transport main string&!! unset
-.cindex "file" "transport for system filter"
-This sets the name of the transport driver that is to be used when the &%save%&
-command in a system message filter specifies a path not ending in &"/"&. During
-the delivery, the variable &$address_file$& contains the path name.
-
-.option system_filter_group main string unset
-.cindex "gid (group id)" "system filter"
-This option is used only when &%system_filter_user%& is also set. It sets the
-gid under which the system filter is run, overriding any gid that is associated
-with the user. The value may be numerical or symbolic.
-
-.option system_filter_pipe_transport main string&!! unset
-.cindex "&(pipe)& transport" "for system filter"
-.vindex "&$address_pipe$&"
-This specifies the transport driver that is to be used when a &%pipe%& command
-is used in a system filter. During the delivery, the variable &$address_pipe$&
-contains the pipe command.
-
-
-.option system_filter_reply_transport main string&!! unset
-.cindex "&(autoreply)& transport" "for system filter"
-This specifies the transport driver that is to be used when a &%mail%& command
-is used in a system filter.
-
-
-.option system_filter_user main string unset
-.cindex "uid (user id)" "system filter"
-If this option is set to root, the system filter is run in the main Exim
-delivery process, as root.  Otherwise, the system filter runs in a separate
-process, as the given user, defaulting to the Exim run-time user.
-Unless the string consists entirely of digits, it
-is looked up in the password data. Failure to find the named user causes a
-configuration error. The gid is either taken from the password data, or
-specified by &%system_filter_group%&. When the uid is specified numerically,
-&%system_filter_group%& is required to be set.
-
-If the system filter generates any pipe, file, or reply deliveries, the uid
-under which the filter is run is used when transporting them, unless a
-transport option overrides.
-
-
-.option tcp_nodelay main boolean true
-.cindex "daemon" "TCP_NODELAY on sockets"
-.cindex "Nagle algorithm"
-.cindex "TCP_NODELAY on listening sockets"
-If this option is set false, it stops the Exim daemon setting the
-TCP_NODELAY option on its listening sockets. Setting TCP_NODELAY
-turns off the &"Nagle algorithm"&, which is a way of improving network
-performance in interactive (character-by-character) situations. Turning it off
-should improve Exim's performance a bit, so that is what happens by default.
-However, it appears that some broken clients cannot cope, and time out. Hence
-this option. It affects only those sockets that are set up for listening by the
-daemon. Sockets created by the smtp transport for delivering mail always set
-TCP_NODELAY.
-
-
-.option timeout_frozen_after main time 0s
-.cindex "frozen messages" "timing out"
-.cindex "timeout" "frozen messages"
-If &%timeout_frozen_after%& is set to a time greater than zero, a frozen
-message of any kind that has been in the queue for longer than the given time
-is automatically cancelled at the next queue run. If the frozen message is a
-bounce message, it is just discarded; otherwise, a bounce is sent to the
-sender, in a similar manner to cancellation by the &%-Mg%& command line option.
-If you want to timeout frozen bounce messages earlier than other kinds of
-frozen message, see &%ignore_bounce_errors_after%&.
-
-&*Note:*& the default value of zero means no timeouts; with this setting,
-frozen messages remain in the queue forever (except for any frozen bounce
-messages that are released by &%ignore_bounce_errors_after%&).
-
-
-.option timezone main string unset
-.cindex "timezone, setting"
-.cindex "environment" "values from"
-The value of &%timezone%& is used to set the environment variable TZ while
-running Exim (if it is different on entry). This ensures that all timestamps
-created by Exim are in the required timezone. If you want all your timestamps
-to be in UTC (aka GMT) you should set
-.code
-timezone = UTC
-.endd
-The default value is taken from TIMEZONE_DEFAULT in &_Local/Makefile_&,
-or, if that is not set, from the value of the TZ environment variable when Exim
-is built. If &%timezone%& is set to the empty string, either at build or run
-time, any existing TZ variable is removed from the environment when Exim
-runs. This is appropriate behaviour for obtaining wall-clock time on some, but
-unfortunately not all, operating systems.
-
-
-.option tls_advertise_hosts main "host list&!!" *
-.cindex "TLS" "advertising"
-.cindex "encryption" "on SMTP connection"
-.cindex "SMTP" "encrypted connection"
-When Exim is built with support for TLS encrypted connections, the availability
-of the STARTTLS command to set up an encrypted session is advertised in
-response to EHLO only to those client hosts that match this option. See
-chapter &<<CHAPTLS>>& for details of Exim's support for TLS.
-Note that the default value requires that a certificate be supplied
-using the &%tls_certificate%& option.  If TLS support for incoming connections
-is not required the &%tls_advertise_hosts%& option should be set empty.
-
-
-.option tls_certificate main string list&!! unset
-.cindex "TLS" "server certificate; location of"
-.cindex "certificate" "server, location of"
-The value of this option is expanded, and must then be a list of absolute paths to
-files which contain the server's certificates (in PEM format).
-Commonly only one file is needed.
-The server's private key is also
-assumed to be in this file if &%tls_privatekey%& is unset. See chapter
-&<<CHAPTLS>>& for further details.
-
-&*Note*&: The certificates defined by this option are used only when Exim is
-receiving incoming messages as a server. If you want to supply certificates for
-use when sending messages as a client, you must set the &%tls_certificate%&
-option in the relevant &(smtp)& transport.
-
-&*Note*&: If you use filenames based on IP addresses, change the list
-separator in the usual way (&<<SECTlistsepchange>>&) to avoid confusion under IPv6.
-
-&*Note*&: Under versions of OpenSSL preceding 1.1.1,
-when a list of more than one
-file is used, the &$tls_in_ourcert$& variable is unreliable.
-The macro "_TLS_BAD_MULTICERT_IN_OURCERT" will be defined for those versions.
-
-If the option contains &$tls_out_sni$& and Exim is built against OpenSSL, then
-if the OpenSSL build supports TLS extensions and the TLS client sends the
-Server Name Indication extension, then this option and others documented in
-&<<SECTtlssni>>& will be re-expanded.
-
-If this option is unset or empty a fresh self-signed certificate will be
-generated for every connection.
-
-.option tls_crl main string&!! unset
-.cindex "TLS" "server certificate revocation list"
-.cindex "certificate" "revocation list for server"
-This option specifies a certificate revocation list. The expanded value must
-be the name of a file that contains CRLs in PEM format.
-
-Under OpenSSL the option can specify a directory with CRL files.
-
-&*Note:*& Under OpenSSL the option must, if given, supply a CRL
-for each signing element of the certificate chain (i.e. all but the leaf).
-For the file variant this can be multiple PEM blocks in the one file.
-
-See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
-
-
-.option tls_dh_max_bits main integer 2236
-.cindex "TLS" "D-H bit count"
-The number of bits used for Diffie-Hellman key-exchange may be suggested by
-the chosen TLS library.  That value might prove to be too high for
-interoperability.  This option provides a maximum clamp on the value
-suggested, trading off security for interoperability.
-
-The value must be at least 1024.
-
-The value 2236 was chosen because, at time of adding the option, it was the
-hard-coded maximum value supported by the NSS cryptographic library, as used
-by Thunderbird, while GnuTLS was suggesting 2432 bits as normal.
-
-If you prefer more security and are willing to break some clients, raise this
-number.
-
-Note that the value passed to GnuTLS for *generating* a new prime may be a
-little less than this figure, because GnuTLS is inexact and may produce a
-larger prime than requested.
-
-
-.option tls_dhparam main string&!! unset
-.cindex "TLS" "D-H parameters for server"
-The value of this option is expanded and indicates the source of DH parameters
-to be used by Exim.
-
-This option is ignored for GnuTLS version 3.6.0 and later.
-The library manages parameter negotiation internally.
-
-&*Note: The Exim Maintainers strongly recommend,
-for other TLS library versions,
-using a filename with site-generated
-local DH parameters*&, which has been supported across all versions of Exim.  The
-other specific constants available are a fallback so that even when
-"unconfigured", Exim can offer Perfect Forward Secrecy in older ciphersuites in TLS.
-
-If &%tls_dhparam%& is a filename starting with a &`/`&,
-then it names a file from which DH
-parameters should be loaded.  If the file exists, it should hold a PEM-encoded
-PKCS#3 representation of the DH prime.  If the file does not exist, for
-OpenSSL it is an error.  For GnuTLS, Exim will attempt to create the file and
-fill it with a generated DH prime.  For OpenSSL, if the DH bit-count from
-loading the file is greater than &%tls_dh_max_bits%& then it will be ignored,
-and treated as though the &%tls_dhparam%& were set to "none".
-
-If this option expands to the string "none", then no DH parameters will be
-loaded by Exim.
-
-If this option expands to the string "historic" and Exim is using GnuTLS, then
-Exim will attempt to load a file from inside the spool directory.  If the file
-does not exist, Exim will attempt to create it.
-See section &<<SECTgnutlsparam>>& for further details.
-
-If Exim is using OpenSSL and this option is empty or unset, then Exim will load
-a default DH prime; the default is Exim-specific but lacks verifiable provenance.
-
-In older versions of Exim the default was the 2048 bit prime described in section
-2.2 of RFC 5114, "2048-bit MODP Group with 224-bit Prime Order Subgroup", which
-in IKE is assigned number 23.
-
-Otherwise, the option must expand to the name used by Exim for any of a number
-of DH primes specified in RFC 2409, RFC 3526, RFC 5114, RFC 7919, or from other
-sources.  As names, Exim uses a standard specified name, else "ike" followed by
-the number used by IKE, or "default" which corresponds to
-&`exim.dev.20160529.3`&.
-
-The available standard primes are:
-&`ffdhe2048`&, &`ffdhe3072`&, &`ffdhe4096`&, &`ffdhe6144`&, &`ffdhe8192`&,
-&`ike1`&, &`ike2`&, &`ike5`&,
-&`ike14`&, &`ike15`&, &`ike16`&, &`ike17`&, &`ike18`&,
-&`ike22`&, &`ike23`& and &`ike24`&.
-
-The available additional primes are:
-&`exim.dev.20160529.1`&, &`exim.dev.20160529.2`& and &`exim.dev.20160529.3`&.
-
-Some of these will be too small to be accepted by clients.
-Some may be too large to be accepted by clients.
-The open cryptographic community has suspicions about the integrity of some
-of the later IKE values, which led into RFC7919 providing new fixed constants
-(the "ffdhe" identifiers).
-
-At this point, all of the "ike" values should be considered obsolete;
-they're still in Exim to avoid breaking unusual configurations, but are
-candidates for removal the next time we have backwards-incompatible changes.
-
-The TLS protocol does not negotiate an acceptable size for this; clients tend
-to hard-drop connections if what is offered by the server is unacceptable,
-whether too large or too small, and there's no provision for the client to
-tell the server what these constraints are.  Thus, as a server operator, you
-need to make an educated guess as to what is most likely to work for your
-userbase.
-
-Some known size constraints suggest that a bit-size in the range 2048 to 2236
-is most likely to maximise interoperability.  The upper bound comes from
-applications using the Mozilla Network Security Services (NSS) library, which
-used to set its &`DH_MAX_P_BITS`& upper-bound to 2236.  This affects many
-mail user agents (MUAs). The lower bound comes from Debian installs of Exim4
-prior to the 4.80 release, as Debian used to patch Exim to raise the minimum
-acceptable bound from 1024 to 2048.
-
-
-.option tls_eccurve main string&!! &`auto`&
-.cindex TLS "EC cryptography"
-This option selects a EC curve for use by Exim when used with OpenSSL.
-It has no effect when Exim is used with GnuTLS.
-
-After expansion it must contain a valid EC curve parameter, such as
-&`prime256v1`&, &`secp384r1`&, or &`P-512`&. Consult your OpenSSL manual
-for valid selections.
-
-For OpenSSL versions before (and not including) 1.0.2, the string
-&`auto`& selects &`prime256v1`&. For more recent OpenSSL versions
-&`auto`& tells the library to choose.
-
-If the option expands to an empty string, no EC curves will be enabled.
-
-
-.option tls_ocsp_file main string&!! unset
-.cindex TLS "certificate status"
-.cindex TLS "OCSP proof file"
-This option
-must if set expand to the absolute path to a file which contains a current
-status proof for the server's certificate, as obtained from the
-Certificate Authority.
-
-Usable for GnuTLS 3.4.4 or 3.3.17 or OpenSSL 1.1.0 (or later).
-The macro "_HAVE_TLS_OCSP" will be defined for those versions.
-
-For OpenSSL 1.1.0 or later, and
-for GnuTLS 3.5.6 or later the expanded value of this option can be a list
-of files, to match a list given for the &%tls_certificate%& option.
-The ordering of the two lists must match.
-The macro "_HAVE_TLS_OCSP_LIST" will be defined for those versions.
-
-The file(s) should be in DER format,
-except for GnuTLS 3.6.3 or later
-or for OpenSSL,
-when an optional filetype prefix can be used.
-The prefix must be one of "DER" or "PEM", followed by
-a single space.  If one is used it sets the format for subsequent
-files in the list; the initial format is DER.
-If multiple proofs are wanted, for multiple chain elements
-(this only works under TLS1.3)
-they must be coded as a combined OCSP response.
-
-Although GnuTLS will accept PEM files with multiple separate
-PEM blobs (ie. separate OCSP responses), it sends them in the
-TLS Certificate record interleaved with the certificates of the chain;
-although a GnuTLS client is happy with that, an OpenSSL client is not.
-
-.option tls_on_connect_ports main "string list" unset
-.cindex SSMTP
-.cindex SMTPS
-This option specifies a list of incoming SSMTP (aka SMTPS) ports that should
-operate the SSMTP (SMTPS) protocol, where a TLS session is immediately
-set up without waiting for the client to issue a STARTTLS command. For
-further details, see section &<<SECTsupobssmt>>&.
-
-
-
-.option tls_privatekey main string list&!! unset
-.cindex "TLS" "server private key; location of"
-The value of this option is expanded, and must then be a list of absolute paths to
-files which contains the server's private keys.
-If this option is unset, or if
-the expansion is forced to fail, or the result is an empty string, the private
-key is assumed to be in the same file as the server's certificates. See chapter
-&<<CHAPTLS>>& for further details.
-
-See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
-
-
-.option tls_remember_esmtp main boolean false
-.cindex "TLS" "esmtp state; remembering"
-.cindex "TLS" "broken clients"
-If this option is set true, Exim violates the RFCs by remembering that it is in
-&"esmtp"& state after successfully negotiating a TLS session. This provides
-support for broken clients that fail to send a new EHLO after starting a
-TLS session.
-
-
-.option tls_require_ciphers main string&!! unset
-.cindex "TLS" "requiring specific ciphers"
-.cindex "cipher" "requiring specific"
-This option controls which ciphers can be used for incoming TLS connections.
-The &(smtp)& transport has an option of the same name for controlling outgoing
-connections. This option is expanded for each connection, so can be varied for
-different clients if required. The value of this option must be a list of
-permitted cipher suites. The OpenSSL and GnuTLS libraries handle cipher control
-in somewhat different ways. If GnuTLS is being used, the client controls the
-preference order of the available ciphers. Details are given in sections
-&<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
-
-
-.option tls_try_verify_hosts main "host list&!!" unset
-.cindex "TLS" "client certificate verification"
-.cindex "certificate" "verification of client"
-See &%tls_verify_hosts%& below.
-
-
-.option tls_verify_certificates main string&!! system
-.cindex "TLS" "client certificate verification"
-.cindex "certificate" "verification of client"
-The value of this option is expanded, and must then be either the
-word "system"
-or the absolute path to
-a file or directory containing permitted certificates for clients that
-match &%tls_verify_hosts%& or &%tls_try_verify_hosts%&.
-
-The "system" value for the option will use a
-system default location compiled into the SSL library.
-This is not available for GnuTLS versions preceding 3.0.20,
-and will be taken as empty; an explicit location
-must be specified.
-
-The use of a directory for the option value is not available for GnuTLS versions
-preceding 3.3.6 and a single file must be used.
-
-With OpenSSL the certificates specified
-explicitly
-either by file or directory
-are added to those given by the system default location.
-
-These certificates should be for the certificate authorities trusted, rather
-than the public cert of individual clients.  With both OpenSSL and GnuTLS, if
-the value is a file then the certificates are sent by Exim as a server to
-connecting clients, defining the list of accepted certificate authorities.
-Thus the values defined should be considered public data.  To avoid this,
-use the explicit directory version.
-
-See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
-
-A forced expansion failure or setting to an empty string is equivalent to
-being unset.
-
-
-.option tls_verify_hosts main "host list&!!" unset
-.cindex "TLS" "client certificate verification"
-.cindex "certificate" "verification of client"
-This option, along with &%tls_try_verify_hosts%&, controls the checking of
-certificates from clients. The expected certificates are defined by
-&%tls_verify_certificates%&, which must be set. A configuration error occurs if
-either &%tls_verify_hosts%& or &%tls_try_verify_hosts%& is set and
-&%tls_verify_certificates%& is not set.
-
-Any client that matches &%tls_verify_hosts%& is constrained by
-&%tls_verify_certificates%&. When the client initiates a TLS session, it must
-present one of the listed certificates. If it does not, the connection is
-aborted. &*Warning*&: Including a host in &%tls_verify_hosts%& does not require
-the host to use TLS. It can still send SMTP commands through unencrypted
-connections. Forcing a client to use TLS has to be done separately using an
-ACL to reject inappropriate commands when the connection is not encrypted.
-
-A weaker form of checking is provided by &%tls_try_verify_hosts%&. If a client
-matches this option (but not &%tls_verify_hosts%&), Exim requests a
-certificate and checks it against &%tls_verify_certificates%&, but does not
-abort the connection if there is no certificate or if it does not match. This
-state can be detected in an ACL, which makes it possible to implement policies
-such as &"accept for relay only if a verified certificate has been received,
-but accept for local delivery if encrypted, even without a verified
-certificate"&.
-
-Client hosts that match neither of these lists are not asked to present
-certificates.
-
-
-.option trusted_groups main "string list&!!" unset
-.cindex "trusted groups"
-.cindex "groups" "trusted"
-This option is expanded just once, at the start of Exim's processing. If this
-option is set, any process that is running in one of the listed groups, or
-which has one of them as a supplementary group, is trusted. The groups can be
-specified numerically or by name. See section &<<SECTtrustedadmin>>& for
-details of what trusted callers are permitted to do. If neither
-&%trusted_groups%& nor &%trusted_users%& is set, only root and the Exim user
-are trusted.
-
-.option trusted_users main "string list&!!" unset
-.cindex "trusted users"
-.cindex "user" "trusted"
-This option is expanded just once, at the start of Exim's processing. If this
-option is set, any process that is running as one of the listed users is
-trusted. The users can be specified numerically or by name. See section
-&<<SECTtrustedadmin>>& for details of what trusted callers are permitted to do.
-If neither &%trusted_groups%& nor &%trusted_users%& is set, only root and the
-Exim user are trusted.
-
-.option unknown_login main string&!! unset
-.cindex "uid (user id)" "unknown caller"
-.vindex "&$caller_uid$&"
-This is a specialized feature for use in unusual configurations. By default, if
-the uid of the caller of Exim cannot be looked up using &[getpwuid()]&, Exim
-gives up. The &%unknown_login%& option can be used to set a login name to be
-used in this circumstance. It is expanded, so values like &%user$caller_uid%&
-can be set. When &%unknown_login%& is used, the value of &%unknown_username%&
-is used for the user's real name (gecos field), unless this has been set by the
-&%-F%& option.
-
-.option unknown_username main string unset
-See &%unknown_login%&.
-
-.option untrusted_set_sender main "address list&!!" unset
-.cindex "trusted users"
-.cindex "sender" "setting by untrusted user"
-.cindex "untrusted user setting sender"
-.cindex "user" "untrusted setting sender"
-.cindex "envelope from"
-.cindex "envelope sender"
-When an untrusted user submits a message to Exim using the standard input, Exim
-normally creates an envelope sender address from the user's login and the
-default qualification domain. Data from the &%-f%& option (for setting envelope
-senders on non-SMTP messages) or the SMTP MAIL command (if &%-bs%& or &%-bS%&
-is used) is ignored.
-
-However, untrusted users are permitted to set an empty envelope sender address,
-to declare that a message should never generate any bounces. For example:
-.code
-exim -f '<>' user@domain.example
-.endd
-.vindex "&$sender_ident$&"
-The &%untrusted_set_sender%& option allows you to permit untrusted users to set
-other envelope sender addresses in a controlled way. When it is set, untrusted
-users are allowed to set envelope sender addresses that match any of the
-patterns in the list. Like all address lists, the string is expanded. The
-identity of the user is in &$sender_ident$&, so you can, for example, restrict
-users to setting senders that start with their login ids
-followed by a hyphen
-by a setting like this:
-.code
-untrusted_set_sender = ^$sender_ident-
-.endd
-If you want to allow untrusted users to set envelope sender addresses without
-restriction, you can use
-.code
-untrusted_set_sender = *
-.endd
-The &%untrusted_set_sender%& option applies to all forms of local input, but
-only to the setting of the envelope sender. It does not permit untrusted users
-to use the other options which trusted user can use to override message
-parameters. Furthermore, it does not stop Exim from removing an existing
-&'Sender:'& header in the message, or from adding a &'Sender:'& header if
-necessary. See &%local_sender_retain%& and &%local_from_check%& for ways of
-overriding these actions. The handling of the &'Sender:'& header is also
-described in section &<<SECTthesenhea>>&.
-
-The log line for a message's arrival shows the envelope sender following
-&"<="&. For local messages, the user's login always follows, after &"U="&. In
-&%-bp%& displays, and in the Exim monitor, if an untrusted user sets an
-envelope sender address, the user's login is shown in parentheses after the
-sender address.
-
-
-.option uucp_from_pattern main string "see below"
-.cindex "&""From""& line"
-.cindex "UUCP" "&""From""& line"
-Some applications that pass messages to an MTA via a command line interface use
-an initial line starting with &"From&~"& to pass the envelope sender. In
-particular, this is used by UUCP software. Exim recognizes such a line by means
-of a regular expression that is set in &%uucp_from_pattern%&. When the pattern
-matches, the sender address is constructed by expanding the contents of
-&%uucp_from_sender%&, provided that the caller of Exim is a trusted user. The
-default pattern recognizes lines in the following two forms:
-.code
-From ph10 Fri Jan  5 12:35 GMT 1996
-From ph10 Fri, 7 Jan 97 14:00:00 GMT
-.endd
-The pattern can be seen by running
-.code
-exim -bP uucp_from_pattern
-.endd
-It checks only up to the hours and minutes, and allows for a 2-digit or 4-digit
-year in the second case. The first word after &"From&~"& is matched in the
-regular expression by a parenthesized subpattern. The default value for
-&%uucp_from_sender%& is &"$1"&, which therefore just uses this first word
-(&"ph10"& in the example above) as the message's sender. See also
-&%ignore_fromline_hosts%&.
-
-
-.option uucp_from_sender main string&!! &`$1`&
-See &%uucp_from_pattern%& above.
-
-
-.option warn_message_file main string unset
-.cindex "warning of delay" "customizing the message"
-.cindex "customizing" "warning message"
-This option defines a template file containing paragraphs of text to be used
-for constructing the warning message which is sent by Exim when a message has
-been in the queue for a specified amount of time, as specified by
-&%delay_warning%&. Details of the file's contents are given in chapter
-&<<CHAPemsgcust>>&. See also &%bounce_message_file%&.
-
-
-.option write_rejectlog main boolean true
-.cindex "reject log" "disabling"
-If this option is set false, Exim no longer writes anything to the reject log.
-See chapter &<<CHAPlog>>& for details of what Exim writes to its logs.
-.ecindex IIDconfima
-.ecindex IIDmaiconf
-
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "Generic options for routers" "CHAProutergeneric"
-.scindex IIDgenoprou1 "options" "generic; for routers"
-.scindex IIDgenoprou2 "generic options" "router"
-This chapter describes the generic options that apply to all routers.
-Those that are preconditions are marked with &Dagger; in the &"use"& field.
-
-For a general description of how a router operates, see sections
-&<<SECTrunindrou>>& and &<<SECTrouprecon>>&. The latter specifies the order in
-which the preconditions are tested. The order of expansion of the options that
-provide data for a transport is: &%errors_to%&, &%headers_add%&,
-&%headers_remove%&, &%transport%&.
-
-
-
-.option address_data routers string&!! unset
-.cindex "router" "data attached to address"
-The string is expanded just before the router is run, that is, after all the
-precondition tests have succeeded. If the expansion is forced to fail, the
-router declines, the value of &%address_data%& remains unchanged, and the
-&%more%& option controls what happens next. Other expansion failures cause
-delivery of the address to be deferred.
-
-.vindex "&$address_data$&"
-When the expansion succeeds, the value is retained with the address, and can be
-accessed using the variable &$address_data$& in the current router, subsequent
-routers, and the eventual transport.
-
-&*Warning*&: If the current or any subsequent router is a &(redirect)& router
-that runs a user's filter file, the contents of &$address_data$& are accessible
-in the filter. This is not normally a problem, because such data is usually
-either not confidential or it &"belongs"& to the current user, but if you do
-put confidential data into &$address_data$& you need to remember this point.
-
-Even if the router declines or passes, the value of &$address_data$& remains
-with the address, though it can be changed by another &%address_data%& setting
-on a subsequent router. If a router generates child addresses, the value of
-&$address_data$& propagates to them. This also applies to the special kind of
-&"child"& that is generated by a router with the &%unseen%& option.
-
-The idea of &%address_data%& is that you can use it to look up a lot of data
-for the address once, and then pick out parts of the data later. For example,
-you could use a single LDAP lookup to return a string of the form
-.code
-uid=1234 gid=5678 mailbox=/mail/xyz forward=/home/xyz/.forward
-.endd
-In the transport you could pick out the mailbox by a setting such as
-.code
-file = ${extract{mailbox}{$address_data}}
-.endd
-This makes the configuration file less messy, and also reduces the number of
-lookups (though Exim does cache lookups).
-
-See also the &%set%& option below.
-
-.vindex "&$sender_address_data$&"
-.vindex "&$address_data$&"
-The &%address_data%& facility is also useful as a means of passing information
-from one router to another, and from a router to a transport. In addition, if
-&$address_data$& is set by a router when verifying a recipient address from an
-ACL, it remains available for use in the rest of the ACL statement. After
-verifying a sender, the value is transferred to &$sender_address_data$&.
-
-
-
-.option address_test routers&!? boolean true
-.oindex "&%-bt%&"
-.cindex "router" "skipping when address testing"
-If this option is set false, the router is skipped when routing is being tested
-by means of the &%-bt%& command line option. This can be a convenience when
-your first router sends messages to an external scanner, because it saves you
-having to set the &"already scanned"& indicator when testing real address
-routing.
-
-
-
-.option cannot_route_message routers string&!! unset
-.cindex "router" "customizing &""cannot route""& message"
-.cindex "customizing" "&""cannot route""& message"
-This option specifies a text message that is used when an address cannot be
-routed because Exim has run out of routers. The default message is
-&"Unrouteable address"&. This option is useful only on routers that have
-&%more%& set false, or on the very last router in a configuration, because the
-value that is used is taken from the last router that is considered. This
-includes a router that is skipped because its preconditions are not met, as
-well as a router that declines. For example, using the default configuration,
-you could put:
-.code
-cannot_route_message = Remote domain not found in DNS
-.endd
-on the first router, which is a &(dnslookup)& router with &%more%& set false,
-and
-.code
-cannot_route_message = Unknown local user
-.endd
-on the final router that checks for local users. If string expansion fails for
-this option, the default message is used. Unless the expansion failure was
-explicitly forced, a message about the failure is written to the main and panic
-logs, in addition to the normal message about the routing failure.
-
-
-.option caseful_local_part routers boolean false
-.cindex "case of local parts"
-.cindex "router" "case of local parts"
-By default, routers handle the local parts of addresses in a case-insensitive
-manner, though the actual case is preserved for transmission with the message.
-If you want the case of letters to be significant in a router, you must set
-this option true. For individual router options that contain address or local
-part lists (for example, &%local_parts%&), case-sensitive matching can be
-turned on by &"+caseful"& as a list item. See section &<<SECTcasletadd>>& for
-more details.
-
-.vindex "&$local_part$&"
-.vindex "&$original_local_part$&"
-.vindex "&$parent_local_part$&"
-The value of the &$local_part$& variable is forced to lower case while a
-router is running unless &%caseful_local_part%& is set. When a router assigns
-an address to a transport, the value of &$local_part$& when the transport runs
-is the same as it was in the router. Similarly, when a router generates child
-addresses by aliasing or forwarding, the values of &$original_local_part$&
-and &$parent_local_part$& are those that were used by the redirecting router.
-
-This option applies to the processing of an address by a router. When a
-recipient address is being processed in an ACL, there is a separate &%control%&
-modifier that can be used to specify case-sensitive processing within the ACL
-(see section &<<SECTcontrols>>&).
-
-
-
-.option check_local_user routers&!? boolean false
-.cindex "local user, checking in router"
-.cindex "router" "checking for local user"
-.cindex "&_/etc/passwd_&"
-.vindex "&$home$&"
-When this option is true, Exim checks that the local part of the recipient
-address (with affixes removed if relevant) is the name of an account on the
-local system. The check is done by calling the &[getpwnam()]& function rather
-than trying to read &_/etc/passwd_& directly. This means that other methods of
-holding password data (such as NIS) are supported. If the local part is a local
-user, &$home$& is set from the password data, and can be tested in other
-preconditions that are evaluated after this one (the order of evaluation is
-given in section &<<SECTrouprecon>>&). However, the value of &$home$& can be
-overridden by &%router_home_directory%&. If the local part is not a local user,
-the router is skipped.
-
-If you want to check that the local part is either the name of a local user
-or matches something else, you cannot combine &%check_local_user%& with a
-setting of &%local_parts%&, because that specifies the logical &'and'& of the
-two conditions. However, you can use a &(passwd)& lookup in a &%local_parts%&
-setting to achieve this. For example:
-.code
-local_parts = passwd;$local_part : lsearch;/etc/other/users
-.endd
-Note, however, that the side effects of &%check_local_user%& (such as setting
-up a home directory) do not occur when a &(passwd)& lookup is used in a
-&%local_parts%& (or any other) precondition.
-
-
-
-.option condition routers&!? string&!! unset
-.cindex "router" "customized precondition"
-This option specifies a general precondition test that has to succeed for the
-router to be called. The &%condition%& option is the last precondition to be
-evaluated (see section &<<SECTrouprecon>>&). The string is expanded, and if the
-result is a forced failure, or an empty string, or one of the strings &"0"& or
-&"no"& or &"false"& (checked without regard to the case of the letters), the
-router is skipped, and the address is offered to the next one.
-
-If the result is any other value, the router is run (as this is the last
-precondition to be evaluated, all the other preconditions must be true).
-
-This option is unusual in that multiple &%condition%& options may be present.
-All &%condition%& options must succeed.
-
-The &%condition%& option provides a means of applying custom conditions to the
-running of routers. Note that in the case of a simple conditional expansion,
-the default expansion values are exactly what is wanted. For example:
-.code
-condition = ${if >{$message_age}{600}}
-.endd
-Because of the default behaviour of the string expansion, this is equivalent to
-.code
-condition = ${if >{$message_age}{600}{true}{}}
-.endd
-
-A multiple condition example, which succeeds:
-.code
-condition = ${if >{$message_age}{600}}
-condition = ${if !eq{${lc:$local_part}}{postmaster}}
-condition = foobar
-.endd
-
-If the expansion fails (other than forced failure) delivery is deferred. Some
-of the other precondition options are common special cases that could in fact
-be specified using &%condition%&.
-
-Historical note: We have &%condition%& on ACLs and on Routers.  Routers
-are far older, and use one set of semantics.  ACLs are newer and when
-they were created, the ACL &%condition%& process was given far stricter
-parse semantics.  The &%bool{}%& expansion condition uses the same rules as
-ACLs.  The &%bool_lax{}%& expansion condition uses the same rules as
-Routers.  More pointedly, the &%bool_lax{}%& was written to match the existing
-Router rules processing behavior.
-
-This is best illustrated in an example:
-.code
-# If used in an ACL condition will fail with a syntax error, but
-# in a router condition any extra characters are treated as a string
-
-$ exim -be '${if eq {${lc:GOOGLE.com}} {google.com}} {yes} {no}}'
-true {yes} {no}}
-
-$ exim -be '${if eq {${lc:WHOIS.com}} {google.com}} {yes} {no}}'
- {yes} {no}}
-.endd
-In each example above, the &%if%& statement actually ends after
-&"{google.com}}"&.  Since no true or false braces were defined, the
-default &%if%& behavior is to return a boolean true or a null answer
-(which evaluates to false). The rest of the line is then treated as a
-string. So the first example resulted in the boolean answer &"true"&
-with the string &" {yes} {no}}"& appended to it. The second example
-resulted in the null output (indicating false) with the string
-&" {yes} {no}}"& appended to it.
-
-In fact you can put excess forward braces in too.  In the router
-&%condition%&, Exim's parser only looks for &"{"& symbols when they
-mean something, like after a &"$"& or when required as part of a
-conditional.  But otherwise &"{"& and &"}"& are treated as ordinary
-string characters.
-
-Thus, in a Router, the above expansion strings will both always evaluate
-true, as the result of expansion is a non-empty string which doesn't
-match an explicit false value.  This can be tricky to debug.  By
-contrast, in an ACL either of those strings will always result in an
-expansion error because the result doesn't look sufficiently boolean.
-
-
-.option debug_print routers string&!! unset
-.cindex "testing" "variables in drivers"
-If this option is set and debugging is enabled (see the &%-d%& command line
-option) or in address-testing mode (see the &%-bt%& command line option),
-the string is expanded and included in the debugging output.
-If expansion of the string fails, the error message is written to the debugging
-output, and Exim carries on processing.
-This option is provided to help with checking out the values of variables and
-so on when debugging router configurations. For example, if a &%condition%&
-option appears not to be working, &%debug_print%& can be used to output the
-variables it references. The output happens after checks for &%domains%&,
-&%local_parts%&, and &%check_local_user%& but before any other preconditions
-are tested. A newline is added to the text if it does not end with one.
-The variable &$router_name$& contains the name of the router.
-
-
-
-.option disable_logging routers boolean false
-If this option is set true, nothing is logged for any routing errors
-or for any deliveries caused by this router. You should not set this option
-unless you really, really know what you are doing. See also the generic
-transport option of the same name.
-
-.option dnssec_request_domains routers "domain list&!!" *
-.cindex "MX record" "security"
-.cindex "DNSSEC" "MX lookup"
-.cindex "security" "MX lookup"
-.cindex "DNS" "DNSSEC"
-DNS lookups for domains matching &%dnssec_request_domains%& will be done with
-the dnssec request bit set.
-This applies to all of the SRV, MX, AAAA, A lookup sequence.
-
-.option dnssec_require_domains routers "domain list&!!" unset
-.cindex "MX record" "security"
-.cindex "DNSSEC" "MX lookup"
-.cindex "security" "MX lookup"
-.cindex "DNS" "DNSSEC"
-DNS lookups for domains matching &%dnssec_require_domains%& will be done with
-the dnssec request bit set.  Any returns not having the Authenticated Data bit
-(AD bit) set will be ignored and logged as a host-lookup failure.
-This applies to all of the SRV, MX, AAAA, A lookup sequence.
-
-
-.option domains routers&!? "domain list&!!" unset
-.cindex "router" "restricting to specific domains"
-.vindex "&$domain_data$&"
-If this option is set, the router is skipped unless the current domain matches
-the list. If the match is achieved by means of a file lookup, the data that the
-lookup returned for the domain is placed in &$domain_data$& for use in string
-expansions of the driver's private options. See section &<<SECTrouprecon>>& for
-a list of the order in which preconditions are evaluated.
-
-
-
-.option driver routers string unset
-This option must always be set. It specifies which of the available routers is
-to be used.
-
-
-.option dsn_lasthop routers boolean false
-.cindex "DSN" "success"
-.cindex "Delivery Status Notification" "success"
-If this option is set true, and extended DSN (RFC3461) processing is in effect,
-Exim will not pass on DSN requests to downstream DSN-aware hosts but will
-instead send a success DSN as if the next hop does not support DSN.
-Not effective on redirect routers.
-
-
-
-.option errors_to routers string&!! unset
-.cindex "envelope from"
-.cindex "envelope sender"
-.cindex "router" "changing address for errors"
-If a router successfully handles an address, it may assign the address to a
-transport for delivery or it may generate child addresses. In both cases, if
-there is a delivery problem during later processing, the resulting bounce
-message is sent to the address that results from expanding this string,
-provided that the address verifies successfully. The &%errors_to%& option is
-expanded before &%headers_add%&, &%headers_remove%&, and &%transport%&.
-
-The &%errors_to%& setting associated with an address can be overridden if it
-subsequently passes through other routers that have their own &%errors_to%&
-settings, or if the message is delivered by a transport with a &%return_path%&
-setting.
-
-If &%errors_to%& is unset, or the expansion is forced to fail, or the result of
-the expansion fails to verify, the errors address associated with the incoming
-address is used. At top level, this is the envelope sender. A non-forced
-expansion failure causes delivery to be deferred.
-
-If an address for which &%errors_to%& has been set ends up being delivered over
-SMTP, the envelope sender for that delivery is the &%errors_to%& value, so that
-any bounces that are generated by other MTAs on the delivery route are also
-sent there. You can set &%errors_to%& to the empty string by either of these
-settings:
-.code
-errors_to =
-errors_to = ""
-.endd
-An expansion item that yields an empty string has the same effect. If you do
-this, a locally detected delivery error for addresses processed by this router
-no longer gives rise to a bounce message; the error is discarded. If the
-address is delivered to a remote host, the return path is set to &`<>`&, unless
-overridden by the &%return_path%& option on the transport.
-
-.vindex "&$address_data$&"
-If for some reason you want to discard local errors, but use a non-empty
-MAIL command for remote delivery, you can preserve the original return
-path in &$address_data$& in the router, and reinstate it in the transport by
-setting &%return_path%&.
-
-The most common use of &%errors_to%& is to direct mailing list bounces to the
-manager of the list, as described in section &<<SECTmailinglists>>&, or to
-implement VERP (Variable Envelope Return Paths) (see section &<<SECTverp>>&).
-
-
-
-.option expn routers&!? boolean true
-.cindex "address" "testing"
-.cindex "testing" "addresses"
-.cindex "EXPN" "router skipping"
-.cindex "router" "skipping for EXPN"
-If this option is turned off, the router is skipped when testing an address
-as a result of processing an SMTP EXPN command. You might, for example,
-want to turn it off on a router for users' &_.forward_& files, while leaving it
-on for the system alias file.
-See section &<<SECTrouprecon>>& for a list of the order in which preconditions
-are evaluated.
-
-The use of the SMTP EXPN command is controlled by an ACL (see chapter
-&<<CHAPACL>>&). When Exim is running an EXPN command, it is similar to testing
-an address with &%-bt%&. Compare VRFY, whose counterpart is &%-bv%&.
-
-
-
-.option fail_verify routers boolean false
-.cindex "router" "forcing verification failure"
-Setting this option has the effect of setting both &%fail_verify_sender%& and
-&%fail_verify_recipient%& to the same value.
-
-
-
-.option fail_verify_recipient routers boolean false
-If this option is true and an address is accepted by this router when
-verifying a recipient, verification fails.
-
-
-
-.option fail_verify_sender routers boolean false
-If this option is true and an address is accepted by this router when
-verifying a sender, verification fails.
-
-
-
-.option fallback_hosts routers "string list" unset
-.cindex "router" "fallback hosts"
-.cindex "fallback" "hosts specified on router"
-String expansion is not applied to this option. The argument must be a
-colon-separated list of host names or IP addresses. The list separator can be
-changed (see section &<<SECTlistsepchange>>&), and a port can be specified with
-each name or address. In fact, the format of each item is exactly the same as
-defined for the list of hosts in a &(manualroute)& router (see section
-&<<SECTformatonehostitem>>&).
-
-If a router queues an address for a remote transport, this host list is
-associated with the address, and used instead of the transport's fallback host
-list. If &%hosts_randomize%& is set on the transport, the order of the list is
-randomized for each use. See the &%fallback_hosts%& option of the &(smtp)&
-transport for further details.
-
-
-.option group routers string&!! "see below"
-.cindex "gid (group id)" "local delivery"
-.cindex "local transports" "uid and gid"
-.cindex "transport" "local"
-.cindex "router" "setting group"
-When a router queues an address for a transport, and the transport does not
-specify a group, the group given here is used when running the delivery
-process.
-The group may be specified numerically or by name. If expansion fails, the
-error is logged and delivery is deferred.
-The default is unset, unless &%check_local_user%& is set, when the default
-is taken from the password information. See also &%initgroups%& and &%user%&
-and the discussion in chapter &<<CHAPenvironment>>&.
-
-
-
-.option headers_add routers list&!! unset
-.cindex "header lines" "adding"
-.cindex "router" "adding header lines"
-This option specifies a list of text headers,
-newline-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
-that is associated with any addresses that are accepted by the router.
-Each item is separately expanded, at routing time.  However, this
-option has no effect when an address is just being verified. The way in which
-the text is used to add header lines at transport time is described in section
-&<<SECTheadersaddrem>>&. New header lines are not actually added until the
-message is in the process of being transported. This means that references to
-header lines in string expansions in the transport's configuration do not
-&"see"& the added header lines.
-
-The &%headers_add%& option is expanded after &%errors_to%&, but before
-&%headers_remove%& and &%transport%&. If an item is empty, or if
-an item expansion is forced to fail, the item has no effect. Other expansion
-failures are treated as configuration errors.
-
-Unlike most options, &%headers_add%& can be specified multiple times
-for a router; all listed headers are added.
-
-&*Warning 1*&: The &%headers_add%& option cannot be used for a &(redirect)&
-router that has the &%one_time%& option set.
-
-.cindex "duplicate addresses"
-.oindex "&%unseen%&"
-&*Warning 2*&: If the &%unseen%& option is set on the router, all header
-additions are deleted when the address is passed on to subsequent routers.
-For a &%redirect%& router, if a generated address is the same as the incoming
-address, this can lead to duplicate addresses with different header
-modifications. Exim does not do duplicate deliveries (except, in certain
-circumstances, to pipes -- see section &<<SECTdupaddr>>&), but it is undefined
-which of the duplicates is discarded, so this ambiguous situation should be
-avoided. The &%repeat_use%& option of the &%redirect%& router may be of help.
-
-
-
-.option headers_remove routers list&!! unset
-.cindex "header lines" "removing"
-.cindex "router" "removing header lines"
-This option specifies a list of text headers,
-colon-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
-that is associated with any addresses that are accepted by the router.
-However, the option has no effect when an address is just being verified.
-Each list item is separately expanded, at transport time.
-.new
-If an item ends in *, it will match any header with the given prefix.
-.wen
-The way in which
-the text is used to remove header lines at transport time is described in
-section &<<SECTheadersaddrem>>&. Header lines are not actually removed until
-the message is in the process of being transported. This means that references
-to header lines in string expansions in the transport's configuration still
-&"see"& the original header lines.
-
-The &%headers_remove%& option is handled after &%errors_to%& and
-&%headers_add%&, but before &%transport%&. If an item expansion is forced to fail,
-the item has no effect. Other expansion failures are treated as configuration
-errors.
-
-Unlike most options, &%headers_remove%& can be specified multiple times
-for a router; all listed headers are removed.
-
-&*Warning 1*&: The &%headers_remove%& option cannot be used for a &(redirect)&
-router that has the &%one_time%& option set.
-
-&*Warning 2*&: If the &%unseen%& option is set on the router, all header
-removal requests are deleted when the address is passed on to subsequent
-routers, and this can lead to problems with duplicates -- see the similar
-warning for &%headers_add%& above.
-
-&*Warning 3*&: Because of the separate expansion of the list items,
-items that contain a list separator must have it doubled.
-To avoid this, change the list separator (&<<SECTlistsepchange>>&).
-
-
-
-.option ignore_target_hosts routers "host list&!!" unset
-.cindex "IP address" "discarding"
-.cindex "router" "discarding IP addresses"
-Although this option is a host list, it should normally contain IP address
-entries rather than names. If any host that is looked up by the router has an
-IP address that matches an item in this list, Exim behaves as if that IP
-address did not exist. This option allows you to cope with rogue DNS entries
-like
-.code
-remote.domain.example.  A  127.0.0.1
-.endd
-by setting
-.code
-ignore_target_hosts = 127.0.0.1
-.endd
-on the relevant router. If all the hosts found by a &(dnslookup)& router are
-discarded in this way, the router declines. In a conventional configuration, an
-attempt to mail to such a domain would normally provoke the &"unrouteable
-domain"& error, and an attempt to verify an address in the domain would fail.
-Similarly, if &%ignore_target_hosts%& is set on an &(ipliteral)& router, the
-router declines if presented with one of the listed addresses.
-
-You can use this option to disable the use of IPv4 or IPv6 for mail delivery by
-means of the first or the second of the following settings, respectively:
-.code
-ignore_target_hosts = 0.0.0.0/0
-ignore_target_hosts = <; 0::0/0
-.endd
-The pattern in the first line matches all IPv4 addresses, whereas the pattern
-in the second line matches all IPv6 addresses.
-
-This option may also be useful for ignoring link-local and site-local IPv6
-addresses. Because, like all host lists, the value of &%ignore_target_hosts%&
-is expanded before use as a list, it is possible to make it dependent on the
-domain that is being routed.
-
-.vindex "&$host_address$&"
-During its expansion, &$host_address$& is set to the IP address that is being
-checked.
-
-.option initgroups routers boolean false
-.cindex "additional groups"
-.cindex "groups" "additional"
-.cindex "local transports" "uid and gid"
-.cindex "transport" "local"
-If the router queues an address for a transport, and this option is true, and
-the uid supplied by the router is not overridden by the transport, the
-&[initgroups()]& function is called when running the transport to ensure that
-any additional groups associated with the uid are set up. See also &%group%&
-and &%user%& and the discussion in chapter &<<CHAPenvironment>>&.
-
-
-
-.option local_part_prefix routers&!? "string list" unset
-.cindex affix "router precondition"
-.cindex "router" "prefix for local part"
-.cindex "prefix" "for local part, used in router"
-If this option is set, the router is skipped unless the local part starts with
-one of the given strings, or &%local_part_prefix_optional%& is true. See
-section &<<SECTrouprecon>>& for a list of the order in which preconditions are
-evaluated.
-
-The list is scanned from left to right, and the first prefix that matches is
-used. A limited form of wildcard is available; if the prefix begins with an
-asterisk, it matches the longest possible sequence of arbitrary characters at
-the start of the local part. An asterisk should therefore always be followed by
-some character that does not occur in normal local parts.
-.cindex "multiple mailboxes"
-.cindex "mailbox" "multiple"
-Wildcarding can be used to set up multiple user mailboxes, as described in
-section &<<SECTmulbox>>&.
-
-.vindex "&$local_part$&"
-.vindex "&$local_part_prefix$&"
-During the testing of the &%local_parts%& option, and while the router is
-running, the prefix is removed from the local part, and is available in the
-expansion variable &$local_part_prefix$&. When a message is being delivered, if
-the router accepts the address, this remains true during subsequent delivery by
-a transport. In particular, the local part that is transmitted in the RCPT
-command for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default.
-This behaviour can be overridden by setting &%rcpt_include_affixes%& true on
-the relevant transport.
-
-.new
-.vindex &$local_part_prefix_v$&
-If wildcarding (above) was used then the part of the prefix matching the
-wildcard is available in &$local_part_prefix_v$&.
-.wen
-
-When an address is being verified, &%local_part_prefix%& affects only the
-behaviour of the router. If the callout feature of verification is in use, this
-means that the full address, including the prefix, will be used during the
-callout.
-
-The prefix facility is commonly used to handle local parts of the form
-&%owner-something%&. Another common use is to support local parts of the form
-&%real-username%& to bypass a user's &_.forward_& file &-- helpful when trying
-to tell a user their forwarding is broken &-- by placing a router like this one
-immediately before the router that handles &_.forward_& files:
-.code
-real_localuser:
-  driver = accept
-  local_part_prefix = real-
-  check_local_user
-  transport = local_delivery
-.endd
-For security, it would probably be a good idea to restrict the use of this
-router to locally-generated messages, using a condition such as this:
-.code
-  condition = ${if match {$sender_host_address}\
-                         {\N^(|127\.0\.0\.1)$\N}}
-.endd
-
-If both &%local_part_prefix%& and &%local_part_suffix%& are set for a router,
-both conditions must be met if not optional. Care must be taken if wildcards
-are used in both a prefix and a suffix on the same router. Different
-separator characters must be used to avoid ambiguity.
-
-
-.option local_part_prefix_optional routers boolean false
-See &%local_part_prefix%& above.
-
-
-
-.option local_part_suffix routers&!? "string list" unset
-.cindex "router" "suffix for local part"
-.cindex "suffix for local part" "used in router"
-This option operates in the same way as &%local_part_prefix%&, except that the
-local part must end (rather than start) with the given string, the
-&%local_part_suffix_optional%& option determines whether the suffix is
-mandatory, and the wildcard * character, if present, must be the last
-character of the suffix. This option facility is commonly used to handle local
-parts of the form &%something-request%& and multiple user mailboxes of the form
-&%username-foo%&.
-
-
-.option local_part_suffix_optional routers boolean false
-See &%local_part_suffix%& above.
-
-
-
-.option local_parts routers&!? "local part list&!!" unset
-.cindex "router" "restricting to specific local parts"
-.cindex "local part" "checking in router"
-The router is run only if the local part of the address matches the list.
-See section &<<SECTrouprecon>>& for a list of the order in which preconditions
-are evaluated, and
-section &<<SECTlocparlis>>& for a discussion of local part lists. Because the
-string is expanded, it is possible to make it depend on the domain, for
-example:
-.code
-local_parts = dbm;/usr/local/specials/$domain
-.endd
-.vindex "&$local_part_data$&"
-If the match is achieved by a lookup, the data that the lookup returned
-for the local part is placed in the variable &$local_part_data$& for use in
-expansions of the router's private options. You might use this option, for
-example, if you have a large number of local virtual domains, and you want to
-send all postmaster mail to the same place without having to set up an alias in
-each virtual domain:
-.code
-postmaster:
-  driver = redirect
-  local_parts = postmaster
-  data = postmaster@real.domain.example
-.endd
-
-
-.option log_as_local routers boolean "see below"
-.cindex "log" "delivery line"
-.cindex "delivery" "log line format"
-Exim has two logging styles for delivery, the idea being to make local
-deliveries stand out more visibly from remote ones. In the &"local"& style, the
-recipient address is given just as the local part, without a domain. The use of
-this style is controlled by this option. It defaults to true for the &(accept)&
-router, and false for all the others. This option applies only when a
-router assigns an address to a transport. It has no effect on routers that
-redirect addresses.
-
-
-
-.option more routers boolean&!! true
-The result of string expansion for this option must be a valid boolean value,
-that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
-result causes an error, and delivery is deferred. If the expansion is forced to
-fail, the default value for the option (true) is used. Other failures cause
-delivery to be deferred.
-
-If this option is set false, and the router declines to handle the address, no
-further routers are tried, routing fails, and the address is bounced.
-.oindex "&%self%&"
-However, if the router explicitly passes an address to the following router by
-means of the setting
-.code
-self = pass
-.endd
-or otherwise, the setting of &%more%& is ignored. Also, the setting of &%more%&
-does not affect the behaviour if one of the precondition tests fails. In that
-case, the address is always passed to the next router.
-
-Note that &%address_data%& is not considered to be a precondition. If its
-expansion is forced to fail, the router declines, and the value of &%more%&
-controls what happens next.
-
-
-.option pass_on_timeout routers boolean false
-.cindex "timeout" "of router"
-.cindex "router" "timeout"
-If a router times out during a host lookup, it normally causes deferral of the
-address. If &%pass_on_timeout%& is set, the address is passed on to the next
-router, overriding &%no_more%&. This may be helpful for systems that are
-intermittently connected to the Internet, or those that want to pass to a smart
-host any messages that cannot immediately be delivered.
-
-There are occasional other temporary errors that can occur while doing DNS
-lookups. They are treated in the same way as a timeout, and this option
-applies to all of them.
-
-
-
-.option pass_router routers string unset
-.cindex "router" "go to after &""pass""&"
-Routers that recognize the generic &%self%& option (&(dnslookup)&,
-&(ipliteral)&, and &(manualroute)&) are able to return &"pass"&, forcing
-routing to continue, and overriding a false setting of &%more%&. When one of
-these routers returns &"pass"&, the address is normally handed on to the next
-router in sequence. This can be changed by setting &%pass_router%& to the name
-of another router. However (unlike &%redirect_router%&) the named router must
-be below the current router, to avoid loops. Note that this option applies only
-to the special case of &"pass"&. It does not apply when a router returns
-&"decline"& because it cannot handle an address.
-
-
-
-.option redirect_router routers string unset
-.cindex "router" "start at after redirection"
-Sometimes an administrator knows that it is pointless to reprocess addresses
-generated from alias or forward files with the same router again. For
-example, if an alias file translates real names into login ids there is no
-point searching the alias file a second time, especially if it is a large file.
-
-The &%redirect_router%& option can be set to the name of any router instance.
-It causes the routing of any generated addresses to start at the named router
-instead of at the first router. This option has no effect if the router in
-which it is set does not generate new addresses.
-
-
-
-.option require_files routers&!? "string list&!!" unset
-.cindex "file" "requiring for router"
-.cindex "router" "requiring file existence"
-This option provides a general mechanism for predicating the running of a
-router on the existence or non-existence of certain files or directories.
-Before running a router, as one of its precondition tests, Exim works its way
-through the &%require_files%& list, expanding each item separately.
-
-Because the list is split before expansion, any colons in expansion items must
-be doubled, or the facility for using a different list separator must be used
-(&<<SECTlistsepchange>>&).
-If any expansion is forced to fail, the item is ignored. Other expansion
-failures cause routing of the address to be deferred.
-
-If any expanded string is empty, it is ignored. Otherwise, except as described
-below, each string must be a fully qualified file path, optionally preceded by
-&"!"&. The paths are passed to the &[stat()]& function to test for the
-existence of the files or directories. The router is skipped if any paths not
-preceded by &"!"& do not exist, or if any paths preceded by &"!"& do exist.
-
-.cindex "NFS"
-If &[stat()]& cannot determine whether a file exists or not, delivery of
-the message is deferred. This can happen when NFS-mounted filesystems are
-unavailable.
-
-This option is checked after the &%domains%&, &%local_parts%&, and &%senders%&
-options, so you cannot use it to check for the existence of a file in which to
-look up a domain, local part, or sender. (See section &<<SECTrouprecon>>& for a
-full list of the order in which preconditions are evaluated.) However, as
-these options are all expanded, you can use the &%exists%& expansion condition
-to make such tests. The &%require_files%& option is intended for checking files
-that the router may be going to use internally, or which are needed by a
-transport (e.g., &_.procmailrc_&).
-
-During delivery, the &[stat()]& function is run as root, but there is a
-facility for some checking of the accessibility of a file by another user.
-This is not a proper permissions check, but just a &"rough"& check that
-operates as follows:
-
-If an item in a &%require_files%& list does not contain any forward slash
-characters, it is taken to be the user (and optional group, separated by a
-comma) to be checked for subsequent files in the list. If no group is specified
-but the user is specified symbolically, the gid associated with the uid is
-used. For example:
-.code
-require_files = mail:/some/file
-require_files = $local_part:$home/.procmailrc
-.endd
-If a user or group name in a &%require_files%& list does not exist, the
-&%require_files%& condition fails.
-
-Exim performs the check by scanning along the components of the file path, and
-checking the access for the given uid and gid. It checks for &"x"& access on
-directories, and &"r"& access on the final file. Note that this means that file
-access control lists, if the operating system has them, are ignored.
-
-&*Warning 1*&: When the router is being run to verify addresses for an
-incoming SMTP message, Exim is not running as root, but under its own uid. This
-may affect the result of a &%require_files%& check. In particular, &[stat()]&
-may yield the error EACCES (&"Permission denied"&). This means that the Exim
-user is not permitted to read one of the directories on the file's path.
-
-&*Warning 2*&: Even when Exim is running as root while delivering a message,
-&[stat()]& can yield EACCES for a file in an NFS directory that is mounted
-without root access. In this case, if a check for access by a particular user
-is requested, Exim creates a subprocess that runs as that user, and tries the
-check again in that process.
-
-The default action for handling an unresolved EACCES is to consider it to
-be caused by a configuration error, and routing is deferred because the
-existence or non-existence of the file cannot be determined. However, in some
-circumstances it may be desirable to treat this condition as if the file did
-not exist. If the filename (or the exclamation mark that precedes the filename
-for non-existence) is preceded by a plus sign, the EACCES error is treated
-as if the file did not exist. For example:
-.code
-require_files = +/some/file
-.endd
-If the router is not an essential part of verification (for example, it
-handles users' &_.forward_& files), another solution is to set the &%verify%&
-option false so that the router is skipped when verifying.
-
-
-
-.option retry_use_local_part routers boolean "see below"
-.cindex "hints database" "retry keys"
-.cindex "local part" "in retry keys"
-When a delivery suffers a temporary routing failure, a retry record is created
-in Exim's hints database. For addresses whose routing depends only on the
-domain, the key for the retry record should not involve the local part, but for
-other addresses, both the domain and the local part should be included.
-Usually, remote routing is of the former kind, and local routing is of the
-latter kind.
-
-This option controls whether the local part is used to form the key for retry
-hints for addresses that suffer temporary errors while being handled by this
-router. The default value is true for any router that has any of
-&%check_local_user%&,
-&%local_parts%&,
-&%condition%&,
-&%local_part_prefix%&,
-&%local_part_suffix%&,
-&%senders%& or
-&%require_files%&
-set, and false otherwise. Note that this option does not apply to hints keys
-for transport delays; they are controlled by a generic transport option of the
-same name.
-
-Failing to set this option when it is needed
-(because a remote router handles only some of the local-parts for a domain)
-can result in incorrect error messages being generated.
-
-The setting of &%retry_use_local_part%& applies only to the router on which it
-appears. If the router generates child addresses, they are routed
-independently; this setting does not become attached to them.
-
-
-
-.option router_home_directory routers string&!! unset
-.cindex "router" "home directory for"
-.cindex "home directory" "for router"
-.vindex "&$home$&"
-This option sets a home directory for use while the router is running. (Compare
-&%transport_home_directory%&, which sets a home directory for later
-transporting.) In particular, if used on a &(redirect)& router, this option
-sets a value for &$home$& while a filter is running. The value is expanded;
-forced expansion failure causes the option to be ignored &-- other failures
-cause the router to defer.
-
-Expansion of &%router_home_directory%& happens immediately after the
-&%check_local_user%& test (if configured), before any further expansions take
-place.
-(See section &<<SECTrouprecon>>& for a list of the order in which preconditions
-are evaluated.)
-While the router is running, &%router_home_directory%& overrides the value of
-&$home$& that came from &%check_local_user%&.
-
-When a router accepts an address and assigns it to a local transport (including
-the cases when a &(redirect)& router generates a pipe, file, or autoreply
-delivery), the home directory setting for the transport is taken from the first
-of these values that is set:
-
-.ilist
-The &%home_directory%& option on the transport;
-.next
-The &%transport_home_directory%& option on the router;
-.next
-The password data if &%check_local_user%& is set on the router;
-.next
-The &%router_home_directory%& option on the router.
-.endlist
-
-In other words, &%router_home_directory%& overrides the password data for the
-router, but not for the transport.
-
-
-
-.option self routers string freeze
-.cindex "MX record" "pointing to local host"
-.cindex "local host" "MX pointing to"
-This option applies to those routers that use a recipient address to find a
-list of remote hosts. Currently, these are the &(dnslookup)&, &(ipliteral)&,
-and &(manualroute)& routers.
-Certain configurations of the &(queryprogram)& router can also specify a list
-of remote hosts.
-Usually such routers are configured to send the message to a remote host via an
-&(smtp)& transport. The &%self%& option specifies what happens when the first
-host on the list turns out to be the local host.
-The way in which Exim checks for the local host is described in section
-&<<SECTreclocipadd>>&.
-
-Normally this situation indicates either an error in Exim's configuration (for
-example, the router should be configured not to process this domain), or an
-error in the DNS (for example, the MX should not point to this host). For this
-reason, the default action is to log the incident, defer the address, and
-freeze the message. The following alternatives are provided for use in special
-cases:
-
-.vlist
-.vitem &%defer%&
-Delivery of the message is tried again later, but the message is not frozen.
-
-.vitem "&%reroute%&: <&'domain'&>"
-The domain is changed to the given domain, and the address is passed back to
-be reprocessed by the routers. No rewriting of headers takes place. This
-behaviour is essentially a redirection.
-
-.vitem "&%reroute: rewrite:%& <&'domain'&>"
-The domain is changed to the given domain, and the address is passed back to be
-reprocessed by the routers. Any headers that contain the original domain are
-rewritten.
-
-.vitem &%pass%&
-.oindex "&%more%&"
-.vindex "&$self_hostname$&"
-The router passes the address to the next router, or to the router named in the
-&%pass_router%& option if it is set. This overrides &%no_more%&. During
-subsequent routing and delivery, the variable &$self_hostname$& contains the
-name of the local host that the router encountered. This can be used to
-distinguish between different cases for hosts with multiple names. The
-combination
-.code
-self = pass
-no_more
-.endd
-ensures that only those addresses that routed to the local host are passed on.
-Without &%no_more%&, addresses that were declined for other reasons would also
-be passed to the next router.
-
-.vitem &%fail%&
-Delivery fails and an error report is generated.
-
-.vitem &%send%&
-.cindex "local host" "sending to"
-The anomaly is ignored and the address is queued for the transport. This
-setting should be used with extreme caution. For an &(smtp)& transport, it
-makes sense only in cases where the program that is listening on the SMTP port
-is not this version of Exim. That is, it must be some other MTA, or Exim with a
-different configuration file that handles the domain in another way.
-.endlist
-
-
-
-.option senders routers&!? "address list&!!" unset
-.cindex "router" "checking senders"
-If this option is set, the router is skipped unless the message's sender
-address matches something on the list.
-See section &<<SECTrouprecon>>& for a list of the order in which preconditions
-are evaluated.
-
-There are issues concerning verification when the running of routers is
-dependent on the sender. When Exim is verifying the address in an &%errors_to%&
-setting, it sets the sender to the null string. When using the &%-bt%& option
-to check a configuration file, it is necessary also to use the &%-f%& option to
-set an appropriate sender. For incoming mail, the sender is unset when
-verifying the sender, but is available when verifying any recipients. If the
-SMTP VRFY command is enabled, it must be used after MAIL if the sender address
-matters.
-
-
-.option set routers "string list" unset
-.cindex router variables
-This option may be used multiple times on a router;
-because of this the list aspect is mostly irrelevant.
-The list separator is a semicolon but can be changed in the
-usual way.
-
-Each list-element given must be of the form &"name = value"&
-and the names used must start with the string &"r_"&.
-Values containing a list-separator should have them doubled.
-When a router runs, the strings are evaluated in order,
-to create variables which are added to the set associated with
-the address.
-The variable is set with the expansion of the value.
-The variables can be used by the router options
-(not including any preconditions)
-and by the transport.
-Later definitions of a given named variable will override former ones.
-Variable use is via the usual &$r_...$& syntax.
-
-This is similar to the &%address_data%& option, except that
-many independent variables can be used, with choice of naming.
-
-
-.option translate_ip_address routers string&!! unset
-.cindex "IP address" "translating"
-.cindex "packet radio"
-.cindex "router" "IP address translation"
-There exist some rare networking situations (for example, packet radio) where
-it is helpful to be able to translate IP addresses generated by normal routing
-mechanisms into other IP addresses, thus performing a kind of manual IP
-routing. This should be done only if the normal IP routing of the TCP/IP stack
-is inadequate or broken. Because this is an extremely uncommon requirement, the
-code to support this option is not included in the Exim binary unless
-SUPPORT_TRANSLATE_IP_ADDRESS=yes is set in &_Local/Makefile_&.
-
-.vindex "&$host_address$&"
-The &%translate_ip_address%& string is expanded for every IP address generated
-by the router, with the generated address set in &$host_address$&. If the
-expansion is forced to fail, no action is taken.
-For any other expansion error, delivery of the message is deferred.
-If the result of the expansion is an IP address, that replaces the original
-address; otherwise the result is assumed to be a host name &-- this is looked
-up using &[gethostbyname()]& (or &[getipnodebyname()]& when available) to
-produce one or more replacement IP addresses. For example, to subvert all IP
-addresses in some specific networks, this could be added to a router:
-.code
-translate_ip_address = \
-  ${lookup{${mask:$host_address/26}}lsearch{/some/file}\
-    {$value}fail}}
-.endd
-The file would contain lines like
-.code
-10.2.3.128/26    some.host
-10.8.4.34/26     10.44.8.15
-.endd
-You should not make use of this facility unless you really understand what you
-are doing.
-
-
-
-.option transport routers string&!! unset
-This option specifies the transport to be used when a router accepts an address
-and sets it up for delivery. A transport is never needed if a router is used
-only for verification. The value of the option is expanded at routing time,
-after the expansion of &%errors_to%&, &%headers_add%&, and &%headers_remove%&,
-and result must be the name of one of the configured transports. If it is not,
-delivery is deferred.
-
-The &%transport%& option is not used by the &(redirect)& router, but it does
-have some private options that set up transports for pipe and file deliveries
-(see chapter &<<CHAPredirect>>&).
-
-
-
-.option transport_current_directory routers string&!! unset
-.cindex "current directory for local transport"
-This option associates a current directory with any address that is routed
-to a local transport. This can happen either because a transport is
-explicitly configured for the router, or because it generates a delivery to a
-file or a pipe. During the delivery process (that is, at transport time), this
-option string is expanded and is set as the current directory, unless
-overridden by a setting on the transport.
-If the expansion fails for any reason, including forced failure, an error is
-logged, and delivery is deferred.
-See chapter &<<CHAPenvironment>>& for details of the local delivery
-environment.
-
-
-
-
-.option transport_home_directory routers string&!! "see below"
-.cindex "home directory" "for local transport"
-This option associates a home directory with any address that is routed to a
-local transport. This can happen either because a transport is explicitly
-configured for the router, or because it generates a delivery to a file or a
-pipe. During the delivery process (that is, at transport time), the option
-string is expanded and is set as the home directory, unless overridden by a
-setting of &%home_directory%& on the transport.
-If the expansion fails for any reason, including forced failure, an error is
-logged, and delivery is deferred.
-
-If the transport does not specify a home directory, and
-&%transport_home_directory%& is not set for the router, the home directory for
-the transport is taken from the password data if &%check_local_user%& is set for
-the router. Otherwise it is taken from &%router_home_directory%& if that option
-is set; if not, no home directory is set for the transport.
-
-See chapter &<<CHAPenvironment>>& for further details of the local delivery
-environment.
-
-
-
-
-.option unseen routers boolean&!! false
-.cindex "router" "carrying on after success"
-The result of string expansion for this option must be a valid boolean value,
-that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
-result causes an error, and delivery is deferred. If the expansion is forced to
-fail, the default value for the option (false) is used. Other failures cause
-delivery to be deferred.
-
-When this option is set true, routing does not cease if the router accepts the
-address. Instead, a copy of the incoming address is passed to the next router,
-overriding a false setting of &%more%&. There is little point in setting
-&%more%& false if &%unseen%& is always true, but it may be useful in cases when
-the value of &%unseen%& contains expansion items (and therefore, presumably, is
-sometimes true and sometimes false).
-
-.cindex "copy of message (&%unseen%& option)"
-Setting the &%unseen%& option has a similar effect to the &%unseen%& command
-qualifier in filter files. It can be used to cause copies of messages to be
-delivered to some other destination, while also carrying out a normal delivery.
-In effect, the current address is made into a &"parent"& that has two children
-&-- one that is delivered as specified by this router, and a clone that goes on
-to be routed further. For this reason, &%unseen%& may not be combined with the
-&%one_time%& option in a &(redirect)& router.
-
-&*Warning*&: Header lines added to the address (or specified for removal) by
-this router or by previous routers affect the &"unseen"& copy of the message
-only. The clone that continues to be processed by further routers starts with
-no added headers and none specified for removal. For a &%redirect%& router, if
-a generated address is the same as the incoming address, this can lead to
-duplicate addresses with different header modifications. Exim does not do
-duplicate deliveries (except, in certain circumstances, to pipes -- see section
-&<<SECTdupaddr>>&), but it is undefined which of the duplicates is discarded,
-so this ambiguous situation should be avoided. The &%repeat_use%& option of the
-&%redirect%& router may be of help.
-
-Unlike the handling of header modifications, any data that was set by the
-&%address_data%& option in the current or previous routers &'is'& passed on to
-subsequent routers.
-
-
-.option user routers string&!! "see below"
-.cindex "uid (user id)" "local delivery"
-.cindex "local transports" "uid and gid"
-.cindex "transport" "local"
-.cindex "router" "user for filter processing"
-.cindex "filter" "user for processing"
-When a router queues an address for a transport, and the transport does not
-specify a user, the user given here is used when running the delivery process.
-The user may be specified numerically or by name. If expansion fails, the
-error is logged and delivery is deferred.
-This user is also used by the &(redirect)& router when running a filter file.
-The default is unset, except when &%check_local_user%& is set. In this case,
-the default is taken from the password information. If the user is specified as
-a name, and &%group%& is not set, the group associated with the user is used.
-See also &%initgroups%& and &%group%& and the discussion in chapter
-&<<CHAPenvironment>>&.
-
-
-
-.option verify routers&!? boolean true
-Setting this option has the effect of setting &%verify_sender%& and
-&%verify_recipient%& to the same value.
-
-
-.option verify_only routers&!? boolean false
-.cindex "EXPN" "with &%verify_only%&"
-.oindex "&%-bv%&"
-.cindex "router" "used only when verifying"
-If this option is set, the router is used only when verifying an address,
-delivering in cutthrough mode or
-testing with the &%-bv%& option, not when actually doing a delivery, testing
-with the &%-bt%& option, or running the SMTP EXPN command. It can be further
-restricted to verifying only senders or recipients by means of
-&%verify_sender%& and &%verify_recipient%&.
-
-&*Warning*&: When the router is being run to verify addresses for an incoming
-SMTP message, Exim is not running as root, but under its own uid. If the router
-accesses any files, you need to make sure that they are accessible to the Exim
-user or group.
-
-
-.option verify_recipient routers&!? boolean true
-If this option is false, the router is skipped when verifying recipient
-addresses,
-delivering in cutthrough mode
-or testing recipient verification using &%-bv%&.
-See section &<<SECTrouprecon>>& for a list of the order in which preconditions
-are evaluated.
-See also the &$verify_mode$& variable.
-
-
-.option verify_sender routers&!? boolean true
-If this option is false, the router is skipped when verifying sender addresses
-or testing sender verification using &%-bvs%&.
-See section &<<SECTrouprecon>>& for a list of the order in which preconditions
-are evaluated.
-See also the &$verify_mode$& variable.
-.ecindex IIDgenoprou1
-.ecindex IIDgenoprou2
-
-
-
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "The accept router" "CHID4"
-.cindex "&(accept)& router"
-.cindex "routers" "&(accept)&"
-The &(accept)& router has no private options of its own. Unless it is being
-used purely for verification (see &%verify_only%&) a transport is required to
-be defined by the generic &%transport%& option. If the preconditions that are
-specified by generic options are met, the router accepts the address and queues
-it for the given transport. The most common use of this router is for setting
-up deliveries to local mailboxes. For example:
-.code
-localusers:
-  driver = accept
-  domains = mydomain.example
-  check_local_user
-  transport = local_delivery
-.endd
-The &%domains%& condition in this example checks the domain of the address, and
-&%check_local_user%& checks that the local part is the login of a local user.
-When both preconditions are met, the &(accept)& router runs, and queues the
-address for the &(local_delivery)& transport.
-
-
-
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "The dnslookup router" "CHAPdnslookup"
-.scindex IIDdnsrou1 "&(dnslookup)& router"
-.scindex IIDdnsrou2 "routers" "&(dnslookup)&"
-The &(dnslookup)& router looks up the hosts that handle mail for the
-recipient's domain in the DNS. A transport must always be set for this router,
-unless &%verify_only%& is set.
-
-If SRV support is configured (see &%check_srv%& below), Exim first searches for
-SRV records. If none are found, or if SRV support is not configured,
-MX records are looked up. If no MX records exist, address records are sought.
-However, &%mx_domains%& can be set to disable the direct use of address
-records.
-
-MX records of equal priority are sorted by Exim into a random order. Exim then
-looks for address records for the host names obtained from MX or SRV records.
-When a host has more than one IP address, they are sorted into a random order,
-except that IPv6 addresses are sorted before IPv4 addresses. If all the
-IP addresses found are discarded by a setting of the &%ignore_target_hosts%&
-generic option, the router declines.
-
-Unless they have the highest priority (lowest MX value), MX records that point
-to the local host, or to any host name that matches &%hosts_treat_as_local%&,
-are discarded, together with any other MX records of equal or lower priority.
-
-.cindex "MX record" "pointing to local host"
-.cindex "local host" "MX pointing to"
-.oindex "&%self%&" "in &(dnslookup)& router"
-If the host pointed to by the highest priority MX record, or looked up as an
-address record, is the local host, or matches &%hosts_treat_as_local%&, what
-happens is controlled by the generic &%self%& option.
-
-
-.section "Problems with DNS lookups" "SECTprowitdnsloo"
-There have been problems with DNS servers when SRV records are looked up.
-Some misbehaving servers return a DNS error or timeout when a non-existent
-SRV record is sought. Similar problems have in the past been reported for
-MX records. The global &%dns_again_means_nonexist%& option can help with this
-problem, but it is heavy-handed because it is a global option.
-
-For this reason, there are two options, &%srv_fail_domains%& and
-&%mx_fail_domains%&, that control what happens when a DNS lookup in a
-&(dnslookup)& router results in a DNS failure or a &"try again"& response. If
-an attempt to look up an SRV or MX record causes one of these results, and the
-domain matches the relevant list, Exim behaves as if the DNS had responded &"no
-such record"&. In the case of an SRV lookup, this means that the router
-proceeds to look for MX records; in the case of an MX lookup, it proceeds to
-look for A or AAAA records, unless the domain matches &%mx_domains%&, in which
-case routing fails.
-
-
-.section "Declining addresses by dnslookup" "SECTdnslookupdecline"
-.cindex "&(dnslookup)& router" "declines"
-There are a few cases where a &(dnslookup)& router will decline to accept
-an address; if such a router is expected to handle "all remaining non-local
-domains", then it is important to set &%no_more%&.
-
-The router will defer rather than decline if the domain
-is found in the &%fail_defer_domains%& router option.
-
-Reasons for a &(dnslookup)& router to decline currently include:
-.ilist
-The domain does not exist in DNS
-.next
-The domain exists but the MX record's host part is just "."; this is a common
-convention (borrowed from SRV) used to indicate that there is no such service
-for this domain and to not fall back to trying A/AAAA records.
-.next
-Ditto, but for SRV records, when &%check_srv%& is set on this router.
-.next
-MX record points to a non-existent host.
-.next
-MX record points to an IP address and the main section option
-&%allow_mx_to_ip%& is not set.
-.next
-MX records exist and point to valid hosts, but all hosts resolve only to
-addresses blocked by the &%ignore_target_hosts%& generic option on this router.
-.next
-The domain is not syntactically valid (see also &%allow_utf8_domains%& and
-&%dns_check_names_pattern%& for handling one variant of this)
-.next
-&%check_secondary_mx%& is set on this router but the local host can
-not be found in the MX records (see below)
-.endlist
-
-
-
-
-.section "Private options for dnslookup" "SECID118"
-.cindex "options" "&(dnslookup)& router"
-The private options for the &(dnslookup)& router are as follows:
-
-.option check_secondary_mx dnslookup boolean false
-.cindex "MX record" "checking for secondary"
-If this option is set, the router declines unless the local host is found in
-(and removed from) the list of hosts obtained by MX lookup. This can be used to
-process domains for which the local host is a secondary mail exchanger
-differently to other domains. The way in which Exim decides whether a host is
-the local host is described in section &<<SECTreclocipadd>>&.
-
-
-.option check_srv dnslookup string&!! unset
-.cindex "SRV record" "enabling use of"
-The &(dnslookup)& router supports the use of SRV records (see RFC 2782) in
-addition to MX and address records. The support is disabled by default. To
-enable SRV support, set the &%check_srv%& option to the name of the service
-required. For example,
-.code
-check_srv = smtp
-.endd
-looks for SRV records that refer to the normal smtp service. The option is
-expanded, so the service name can vary from message to message or address
-to address. This might be helpful if SRV records are being used for a
-submission service. If the expansion is forced to fail, the &%check_srv%&
-option is ignored, and the router proceeds to look for MX records in the
-normal way.
-
-When the expansion succeeds, the router searches first for SRV records for
-the given service (it assumes TCP protocol). A single SRV record with a
-host name that consists of just a single dot indicates &"no such service for
-this domain"&; if this is encountered, the router declines. If other kinds of
-SRV record are found, they are used to construct a host list for delivery
-according to the rules of RFC 2782. MX records are not sought in this case.
-
-When no SRV records are found, MX records (and address records) are sought in
-the traditional way. In other words, SRV records take precedence over MX
-records, just as MX records take precedence over address records. Note that
-this behaviour is not sanctioned by RFC 2782, though a previous draft RFC
-defined it. It is apparently believed that MX records are sufficient for email
-and that SRV records should not be used for this purpose. However, SRV records
-have an additional &"weight"& feature which some people might find useful when
-trying to split an SMTP load between hosts of different power.
-
-See section &<<SECTprowitdnsloo>>& above for a discussion of Exim's behaviour
-when there is a DNS lookup error.
-
-
-
-
-.option fail_defer_domains dnslookup "domain list&!!" unset
-.cindex "MX record" "not found"
-DNS lookups for domains matching &%fail_defer_domains%&
-which find no matching record will cause the router to defer
-rather than the default behaviour of decline.
-This maybe be useful for queueing messages for a newly created
-domain while the DNS configuration is not ready.
-However, it will result in any message with mistyped domains
-also being queued.
-
-
-.option ipv4_only "string&!!" unset
-.cindex IPv6 disabling
-.cindex DNS "IPv6 disabling"
-The string is expanded, and if the result is anything but a forced failure,
-or an empty string, or one of the strings “0” or “no” or “false”
-(checked without regard to the case of the letters),
-only A records are used.
-
-.option ipv4_prefer "string&!!" unset
-.cindex IPv4 preference
-.cindex DNS "IPv4 preference"
-The string is expanded, and if the result is anything but a forced failure,
-or an empty string, or one of the strings “0” or “no” or “false”
-(checked without regard to the case of the letters),
-A records are sorted before AAAA records (inverting the default).
-
-.option mx_domains dnslookup "domain list&!!" unset
-.cindex "MX record" "required to exist"
-.cindex "SRV record" "required to exist"
-A domain that matches &%mx_domains%& is required to have either an MX or an SRV
-record in order to be recognized. (The name of this option could be improved.)
-For example, if all the mail hosts in &'fict.example'& are known to have MX
-records, except for those in &'discworld.fict.example'&, you could use this
-setting:
-.code
-mx_domains = ! *.discworld.fict.example : *.fict.example
-.endd
-This specifies that messages addressed to a domain that matches the list but
-has no MX record should be bounced immediately instead of being routed using
-the address record.
-
-
-.option mx_fail_domains dnslookup "domain list&!!" unset
-If the DNS lookup for MX records for one of the domains in this list causes a
-DNS lookup error, Exim behaves as if no MX records were found. See section
-&<<SECTprowitdnsloo>>& for more discussion.
-
-
-
-
-.option qualify_single dnslookup boolean true
-.cindex "DNS" "resolver options"
-.cindex "DNS" "qualifying single-component names"
-When this option is true, the resolver option RES_DEFNAMES is set for DNS
-lookups. Typically, but not standardly, this causes the resolver to qualify
-single-component names with the default domain. For example, on a machine
-called &'dictionary.ref.example'&, the domain &'thesaurus'& would be changed to
-&'thesaurus.ref.example'& inside the resolver. For details of what your
-resolver actually does, consult your man pages for &'resolver'& and
-&'resolv.conf'&.
-
-
-
-.option rewrite_headers dnslookup boolean true
-.cindex "rewriting" "header lines"
-.cindex "header lines" "rewriting"
-If the domain name in the address that is being processed is not fully
-qualified, it may be expanded to its full form by a DNS lookup. For example, if
-an address is specified as &'dormouse@teaparty'&, the domain might be
-expanded to &'teaparty.wonderland.fict.example'&. Domain expansion can also
-occur as a result of setting the &%widen_domains%& option. If
-&%rewrite_headers%& is true, all occurrences of the abbreviated domain name in
-any &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-to:'&, &'Sender:'&, and &'To:'&
-header lines of the message are rewritten with the full domain name.
-
-This option should be turned off only when it is known that no message is
-ever going to be sent outside an environment where the abbreviation makes
-sense.
-
-When an MX record is looked up in the DNS and matches a wildcard record, name
-servers normally return a record containing the name that has been looked up,
-making it impossible to detect whether a wildcard was present or not. However,
-some name servers have recently been seen to return the wildcard entry. If the
-name returned by a DNS lookup begins with an asterisk, it is not used for
-header rewriting.
-
-
-.option same_domain_copy_routing dnslookup boolean false
-.cindex "address" "copying routing"
-Addresses with the same domain are normally routed by the &(dnslookup)& router
-to the same list of hosts. However, this cannot be presumed, because the router
-options and preconditions may refer to the local part of the address. By
-default, therefore, Exim routes each address in a message independently. DNS
-servers run caches, so repeated DNS lookups are not normally expensive, and in
-any case, personal messages rarely have more than a few recipients.
-
-If you are running mailing lists with large numbers of subscribers at the same
-domain, and you are using a &(dnslookup)& router which is independent of the
-local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
-lookups for identical domains in one message. In this case, when &(dnslookup)&
-routes an address to a remote transport, any other unrouted addresses in the
-message that have the same domain are automatically given the same routing
-without processing them independently,
-provided the following conditions are met:
-
-.ilist
-No router that processed the address specified &%headers_add%& or
-&%headers_remove%&.
-.next
-The router did not change the address in any way, for example, by &"widening"&
-the domain.
-.endlist
-
-
-
-
-.option search_parents dnslookup boolean false
-.cindex "DNS" "resolver options"
-When this option is true, the resolver option RES_DNSRCH is set for DNS
-lookups. This is different from the &%qualify_single%& option in that it
-applies to domains containing dots. Typically, but not standardly, it causes
-the resolver to search for the name in the current domain and in parent
-domains. For example, on a machine in the &'fict.example'& domain, if looking
-up &'teaparty.wonderland'& failed, the resolver would try
-&'teaparty.wonderland.fict.example'&. For details of what your resolver
-actually does, consult your man pages for &'resolver'& and &'resolv.conf'&.
-
-Setting this option true can cause problems in domains that have a wildcard MX
-record, because any domain that does not have its own MX record matches the
-local wildcard.
-
-
-
-.option srv_fail_domains dnslookup "domain list&!!" unset
-If the DNS lookup for SRV records for one of the domains in this list causes a
-DNS lookup error, Exim behaves as if no SRV records were found. See section
-&<<SECTprowitdnsloo>>& for more discussion.
-
-
-
-
-.option widen_domains dnslookup "string list" unset
-.cindex "domain" "partial; widening"
-If a DNS lookup fails and this option is set, each of its strings in turn is
-added onto the end of the domain, and the lookup is tried again. For example,
-if
-.code
-widen_domains = fict.example:ref.example
-.endd
-is set and a lookup of &'klingon.dictionary'& fails,
-&'klingon.dictionary.fict.example'& is looked up, and if this fails,
-&'klingon.dictionary.ref.example'& is tried. Note that the &%qualify_single%&
-and &%search_parents%& options can cause some widening to be undertaken inside
-the DNS resolver. &%widen_domains%& is not applied to sender addresses
-when verifying, unless &%rewrite_headers%& is false (not the default).
-
-
-.section "Effect of qualify_single and search_parents" "SECID119"
-When a domain from an envelope recipient is changed by the resolver as a result
-of the &%qualify_single%& or &%search_parents%& options, Exim rewrites the
-corresponding address in the message's header lines unless &%rewrite_headers%&
-is set false. Exim then re-routes the address, using the full domain.
-
-These two options affect only the DNS lookup that takes place inside the router
-for the domain of the address that is being routed. They do not affect lookups
-such as that implied by
-.code
-domains = @mx_any
-.endd
-that may happen while processing a router precondition before the router is
-entered. No widening ever takes place for these lookups.
-.ecindex IIDdnsrou1
-.ecindex IIDdnsrou2
-
-
-
-
-
-
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "The ipliteral router" "CHID5"
-.cindex "&(ipliteral)& router"
-.cindex "domain literal" "routing"
-.cindex "routers" "&(ipliteral)&"
-This router has no private options. Unless it is being used purely for
-verification (see &%verify_only%&) a transport is required to be defined by the
-generic &%transport%& option. The router accepts the address if its domain part
-takes the form of an RFC 2822 domain literal. For example, the &(ipliteral)&
-router handles the address
-.code
-root@[192.168.1.1]
-.endd
-by setting up delivery to the host with that IP address. IPv4 domain literals
-consist of an IPv4 address enclosed in square brackets. IPv6 domain literals
-are similar, but the address is preceded by &`ipv6:`&. For example:
-.code
-postmaster@[ipv6:fe80::a00:20ff:fe86:a061.5678]
-.endd
-Exim allows &`ipv4:`& before IPv4 addresses, for consistency, and on the
-grounds that sooner or later somebody will try it.
-
-.oindex "&%self%&" "in &(ipliteral)& router"
-If the IP address matches something in &%ignore_target_hosts%&, the router
-declines. If an IP literal turns out to refer to the local host, the generic
-&%self%& option determines what happens.
-
-The RFCs require support for domain literals; however, their use is
-controversial in today's Internet. If you want to use this router, you must
-also set the main configuration option &%allow_domain_literals%&. Otherwise,
-Exim will not recognize the domain literal syntax in addresses.
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "The iplookup router" "CHID6"
-.cindex "&(iplookup)& router"
-.cindex "routers" "&(iplookup)&"
-The &(iplookup)& router was written to fulfil a specific requirement in
-Cambridge University (which in fact no longer exists). For this reason, it is
-not included in the binary of Exim by default. If you want to include it, you
-must set
-.code
-ROUTER_IPLOOKUP=yes
-.endd
-in your &_Local/Makefile_& configuration file.
-
-The &(iplookup)& router routes an address by sending it over a TCP or UDP
-connection to one or more specific hosts. The host can then return the same or
-a different address &-- in effect rewriting the recipient address in the
-message's envelope. The new address is then passed on to subsequent routers. If
-this process fails, the address can be passed on to other routers, or delivery
-can be deferred. Since &(iplookup)& is just a rewriting router, a transport
-must not be specified for it.
-
-.cindex "options" "&(iplookup)& router"
-.option hosts iplookup string unset
-This option must be supplied. Its value is a colon-separated list of host
-names. The hosts are looked up using &[gethostbyname()]&
-(or &[getipnodebyname()]& when available)
-and are tried in order until one responds to the query. If none respond, what
-happens is controlled by &%optional%&.
-
-
-.option optional iplookup boolean false
-If &%optional%& is true, if no response is obtained from any host, the address
-is passed to the next router, overriding &%no_more%&. If &%optional%& is false,
-delivery to the address is deferred.
-
-
-.option port iplookup integer 0
-.cindex "port" "&(iplookup)& router"
-This option must be supplied. It specifies the port number for the TCP or UDP
-call.
-
-
-.option protocol iplookup string udp
-This option can be set to &"udp"& or &"tcp"& to specify which of the two
-protocols is to be used.
-
-
-.option query iplookup string&!! "see below"
-This defines the content of the query that is sent to the remote hosts. The
-default value is:
-.code
-$local_part@$domain $local_part@$domain
-.endd
-The repetition serves as a way of checking that a response is to the correct
-query in the default case (see &%response_pattern%& below).
-
-
-.option reroute iplookup string&!! unset
-If this option is not set, the rerouted address is precisely the byte string
-returned by the remote host, up to the first white space, if any. If set, the
-string is expanded to form the rerouted address. It can include parts matched
-in the response by &%response_pattern%& by means of numeric variables such as
-&$1$&, &$2$&, etc. The variable &$0$& refers to the entire input string,
-whether or not a pattern is in use. In all cases, the rerouted address must end
-up in the form &'local_part@domain'&.
-
-
-.option response_pattern iplookup string unset
-This option can be set to a regular expression that is applied to the string
-returned from the remote host. If the pattern does not match the response, the
-router declines. If &%response_pattern%& is not set, no checking of the
-response is done, unless the query was defaulted, in which case there is a
-check that the text returned after the first white space is the original
-address. This checks that the answer that has been received is in response to
-the correct question. For example, if the response is just a new domain, the
-following could be used:
-.code
-response_pattern = ^([^@]+)$
-reroute = $local_part@$1
-.endd
-
-.option timeout iplookup time 5s
-This specifies the amount of time to wait for a response from the remote
-machine. The same timeout is used for the &[connect()]& function for a TCP
-call. It does not apply to UDP.
-
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "The manualroute router" "CHID7"
-.scindex IIDmanrou1 "&(manualroute)& router"
-.scindex IIDmanrou2 "routers" "&(manualroute)&"
-.cindex "domain" "manually routing"
-The &(manualroute)& router is so-called because it provides a way of manually
-routing an address according to its domain. It is mainly used when you want to
-route addresses to remote hosts according to your own rules, bypassing the
-normal DNS routing that looks up MX records. However, &(manualroute)& can also
-route to local transports, a facility that may be useful if you want to save
-messages for dial-in hosts in local files.
-
-The &(manualroute)& router compares a list of domain patterns with the domain
-it is trying to route. If there is no match, the router declines. Each pattern
-has associated with it a list of hosts and some other optional data, which may
-include a transport. The combination of a pattern and its data is called a
-&"routing rule"&. For patterns that do not have an associated transport, the
-generic &%transport%& option must specify a transport, unless the router is
-being used purely for verification (see &%verify_only%&).
-
-.vindex "&$host$&"
-In the case of verification, matching the domain pattern is sufficient for the
-router to accept the address. When actually routing an address for delivery,
-an address that matches a domain pattern is queued for the associated
-transport. If the transport is not a local one, a host list must be associated
-with the pattern; IP addresses are looked up for the hosts, and these are
-passed to the transport along with the mail address. For local transports, a
-host list is optional. If it is present, it is passed in &$host$& as a single
-text string.
-
-The list of routing rules can be provided as an inline string in
-&%route_list%&, or the data can be obtained by looking up the domain in a file
-or database by setting &%route_data%&. Only one of these settings may appear in
-any one instance of &(manualroute)&. The format of routing rules is described
-below, following the list of private options.
-
-
-.section "Private options for manualroute" "SECTprioptman"
-
-.cindex "options" "&(manualroute)& router"
-The private options for the &(manualroute)& router are as follows:
-
-.option host_all_ignored manualroute string defer
-See &%host_find_failed%&.
-
-.option host_find_failed manualroute string freeze
-This option controls what happens when &(manualroute)& tries to find an IP
-address for a host, and the host does not exist. The option can be set to one
-of the following values:
-.code
-decline
-defer
-fail
-freeze
-ignore
-pass
-.endd
-The default (&"freeze"&) assumes that this state is a serious configuration
-error. The difference between &"pass"& and &"decline"& is that the former
-forces the address to be passed to the next router (or the router defined by
-&%pass_router%&),
-.oindex "&%more%&"
-overriding &%no_more%&, whereas the latter passes the address to the next
-router only if &%more%& is true.
-
-The value &"ignore"& causes Exim to completely ignore a host whose IP address
-cannot be found. If all the hosts in the list are ignored, the behaviour is
-controlled by the &%host_all_ignored%& option. This takes the same values
-as &%host_find_failed%&, except that it cannot be set to &"ignore"&.
-
-The &%host_find_failed%& option applies only to a definite &"does not exist"&
-state; if a host lookup gets a temporary error, delivery is deferred unless the
-generic &%pass_on_timeout%& option is set.
-
-
-.option hosts_randomize manualroute boolean false
-.cindex "randomized host list"
-.cindex "host" "list of; randomized"
-If this option is set, the order of the items in a host list in a routing rule
-is randomized each time the list is used, unless an option in the routing rule
-overrides (see below). Randomizing the order of a host list can be used to do
-crude load sharing. However, if more than one mail address is routed by the
-same router to the same host list, the host lists are considered to be the same
-(even though they may be randomized into different orders) for the purpose of
-deciding whether to batch the deliveries into a single SMTP transaction.
-
-When &%hosts_randomize%& is true, a host list may be split
-into groups whose order is separately randomized. This makes it possible to
-set up MX-like behaviour. The boundaries between groups are indicated by an
-item that is just &`+`& in the host list. For example:
-.code
-route_list = * host1:host2:host3:+:host4:host5
-.endd
-The order of the first three hosts and the order of the last two hosts is
-randomized for each use, but the first three always end up before the last two.
-If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored. If a
-randomized host list is passed to an &(smtp)& transport that also has
-&%hosts_randomize set%&, the list is not re-randomized.
-
-
-.option route_data manualroute string&!! unset
-If this option is set, it must expand to yield the data part of a routing rule.
-Typically, the expansion string includes a lookup based on the domain. For
-example:
-.code
-route_data = ${lookup{$domain}dbm{/etc/routes}}
-.endd
-If the expansion is forced to fail, or the result is an empty string, the
-router declines. Other kinds of expansion failure cause delivery to be
-deferred.
-
-
-.option route_list manualroute "string list" unset
-This string is a list of routing rules, in the form defined below. Note that,
-unlike most string lists, the items are separated by semicolons. This is so
-that they may contain colon-separated host lists.
-
-
-.option same_domain_copy_routing manualroute boolean false
-.cindex "address" "copying routing"
-Addresses with the same domain are normally routed by the &(manualroute)&
-router to the same list of hosts. However, this cannot be presumed, because the
-router options and preconditions may refer to the local part of the address. By
-default, therefore, Exim routes each address in a message independently. DNS
-servers run caches, so repeated DNS lookups are not normally expensive, and in
-any case, personal messages rarely have more than a few recipients.
-
-If you are running mailing lists with large numbers of subscribers at the same
-domain, and you are using a &(manualroute)& router which is independent of the
-local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
-lookups for identical domains in one message. In this case, when
-&(manualroute)& routes an address to a remote transport, any other unrouted
-addresses in the message that have the same domain are automatically given the
-same routing without processing them independently. However, this is only done
-if &%headers_add%& and &%headers_remove%& are unset.
-
-
-
-
-.section "Routing rules in route_list" "SECID120"
-The value of &%route_list%& is a string consisting of a sequence of routing
-rules, separated by semicolons. If a semicolon is needed in a rule, it can be
-entered as two semicolons. Alternatively, the list separator can be changed as
-described (for colon-separated lists) in section &<<SECTlistconstruct>>&.
-Empty rules are ignored. The format of each rule is
-.display
-<&'domain pattern'&>  <&'list of hosts'&>  <&'options'&>
-.endd
-The following example contains two rules, each with a simple domain pattern and
-no options:
-.code
-route_list = \
-  dict.ref.example  mail-1.ref.example:mail-2.ref.example ; \
-  thes.ref.example  mail-3.ref.example:mail-4.ref.example
-.endd
-The three parts of a rule are separated by white space. The pattern and the
-list of hosts can be enclosed in quotes if necessary, and if they are, the
-usual quoting rules apply. Each rule in a &%route_list%& must start with a
-single domain pattern, which is the only mandatory item in the rule. The
-pattern is in the same format as one item in a domain list (see section
-&<<SECTdomainlist>>&),
-except that it may not be the name of an interpolated file.
-That is, it may be wildcarded, or a regular expression, or a file or database
-lookup (with semicolons doubled, because of the use of semicolon as a separator
-in a &%route_list%&).
-
-The rules in &%route_list%& are searched in order until one of the patterns
-matches the domain that is being routed. The list of hosts and then options are
-then used as described below. If there is no match, the router declines. When
-&%route_list%& is set, &%route_data%& must not be set.
-
-
-
-.section "Routing rules in route_data" "SECID121"
-The use of &%route_list%& is convenient when there are only a small number of
-routing rules. For larger numbers, it is easier to use a file or database to
-hold the routing information, and use the &%route_data%& option instead.
-The value of &%route_data%& is a list of hosts, followed by (optional) options.
-Most commonly, &%route_data%& is set as a string that contains an
-expansion lookup. For example, suppose we place two routing rules in a file
-like this:
-.code
-dict.ref.example:  mail-1.ref.example:mail-2.ref.example
-thes.ref.example:  mail-3.ref.example:mail-4.ref.example
-.endd
-This data can be accessed by setting
-.code
-route_data = ${lookup{$domain}lsearch{/the/file/name}}
-.endd
-Failure of the lookup results in an empty string, causing the router to
-decline. However, you do not have to use a lookup in &%route_data%&. The only
-requirement is that the result of expanding the string is a list of hosts,
-possibly followed by options, separated by white space. The list of hosts must
-be enclosed in quotes if it contains white space.
-
-
-
-
-.section "Format of the list of hosts" "SECID122"
-A list of hosts, whether obtained via &%route_data%& or &%route_list%&, is
-always separately expanded before use. If the expansion fails, the router
-declines. The result of the expansion must be a colon-separated list of names
-and/or IP addresses, optionally also including ports.
-If the list is written with spaces, it must be protected with quotes.
-The format of each item
-in the list is described in the next section. The list separator can be changed
-as described in section &<<SECTlistsepchange>>&.
-
-If the list of hosts was obtained from a &%route_list%& item, the following
-variables are set during its expansion:
-
-.ilist
-.cindex "numerical variables (&$1$& &$2$&  etc)" "in &(manualroute)& router"
-If the domain was matched against a regular expression, the numeric variables
-&$1$&, &$2$&, etc. may be set. For example:
-.code
-route_list = ^domain(\d+)   host-$1.text.example
-.endd
-.next
-&$0$& is always set to the entire domain.
-.next
-&$1$& is also set when partial matching is done in a file lookup.
-
-.next
-.vindex "&$value$&"
-If the pattern that matched the domain was a lookup item, the data that was
-looked up is available in the expansion variable &$value$&. For example:
-.code
-route_list = lsearch;;/some/file.routes  $value
-.endd
-.endlist
-
-Note the doubling of the semicolon in the pattern that is necessary because
-semicolon is the default route list separator.
-
-
-
-.section "Format of one host item" "SECTformatonehostitem"
-Each item in the list of hosts can be either a host name or an IP address,
-optionally with an attached port number, or it can be a single "+"
-(see &%hosts_randomize%&).
-When no port is given, an IP address
-is not enclosed in brackets. When a port is specified, it overrides the port
-specification on the transport. The port is separated from the name or address
-by a colon. This leads to some complications:
-
-.ilist
-Because colon is the default separator for the list of hosts, either
-the colon that specifies a port must be doubled, or the list separator must
-be changed. The following two examples have the same effect:
-.code
-route_list = * "host1.tld::1225 : host2.tld::1226"
-route_list = * "<+ host1.tld:1225 + host2.tld:1226"
-.endd
-.next
-When IPv6 addresses are involved, it gets worse, because they contain
-colons of their own. To make this case easier, it is permitted to
-enclose an IP address (either v4 or v6) in square brackets if a port
-number follows. For example:
-.code
-route_list = * "</ [10.1.1.1]:1225 / [::1]:1226"
-.endd
-.endlist
-
-.section "How the list of hosts is used" "SECThostshowused"
-When an address is routed to an &(smtp)& transport by &(manualroute)&, each of
-the hosts is tried, in the order specified, when carrying out the SMTP
-delivery. However, the order can be changed by setting the &%hosts_randomize%&
-option, either on the router (see section &<<SECTprioptman>>& above), or on the
-transport.
-
-Hosts may be listed by name or by IP address. An unadorned name in the list of
-hosts is interpreted as a host name. A name that is followed by &`/MX`& is
-interpreted as an indirection to a sublist of hosts obtained by looking up MX
-records in the DNS. For example:
-.code
-route_list = *  x.y.z:p.q.r/MX:e.f.g
-.endd
-If this feature is used with a port specifier, the port must come last. For
-example:
-.code
-route_list = *  dom1.tld/mx::1225
-.endd
-If the &%hosts_randomize%& option is set, the order of the items in the list is
-randomized before any lookups are done. Exim then scans the list; for any name
-that is not followed by &`/MX`& it looks up an IP address. If this turns out to
-be an interface on the local host and the item is not the first in the list,
-Exim discards it and any subsequent items. If it is the first item, what
-happens is controlled by the
-.oindex "&%self%&" "in &(manualroute)& router"
-&%self%& option of the router.
-
-A name on the list that is followed by &`/MX`& is replaced with the list of
-hosts obtained by looking up MX records for the name. This is always a DNS
-lookup; the &%bydns%& and &%byname%& options (see section &<<SECThowoptused>>&
-below) are not relevant here. The order of these hosts is determined by the
-preference values in the MX records, according to the usual rules. Because
-randomizing happens before the MX lookup, it does not affect the order that is
-defined by MX preferences.
-
-If the local host is present in the sublist obtained from MX records, but is
-not the most preferred host in that list, it and any equally or less
-preferred hosts are removed before the sublist is inserted into the main list.
-
-If the local host is the most preferred host in the MX list, what happens
-depends on where in the original list of hosts the &`/MX`& item appears. If it
-is not the first item (that is, there are previous hosts in the main list),
-Exim discards this name and any subsequent items in the main list.
-
-If the MX item is first in the list of hosts, and the local host is the
-most preferred host, what happens is controlled by the &%self%& option of the
-router.
-
-DNS failures when lookup up the MX records are treated in the same way as DNS
-failures when looking up IP addresses: &%pass_on_timeout%& and
-&%host_find_failed%& are used when relevant.
-
-The generic &%ignore_target_hosts%& option applies to all hosts in the list,
-whether obtained from an MX lookup or not.
-
-
-
-.section "How the options are used" "SECThowoptused"
-The options are a sequence of words, space-separated.
-One of the words can be the name of a transport; this overrides the
-&%transport%& option on the router for this particular routing rule only. The
-other words (if present) control randomization of the list of hosts on a
-per-rule basis, and how the IP addresses of the hosts are to be found when
-routing to a remote transport. These options are as follows:
-
-.ilist
-&%randomize%&: randomize the order of the hosts in this list, overriding the
-setting of &%hosts_randomize%& for this routing rule only.
-.next
-&%no_randomize%&: do not randomize the order of the hosts in this list,
-overriding the setting of &%hosts_randomize%& for this routing rule only.
-.next
-&%byname%&: use &[getipnodebyname()]& (&[gethostbyname()]& on older systems) to
-find IP addresses. This function may ultimately cause a DNS lookup, but it may
-also look in &_/etc/hosts_& or other sources of information.
-.next
-&%bydns%&: look up address records for the hosts directly in the DNS; fail if
-no address records are found. If there is a temporary DNS error (such as a
-timeout), delivery is deferred.
-.next
-&%ipv4_only%&: in direct DNS lookups, look up only A records.
-.next
-&%ipv4_prefer%&: in direct DNS lookups, sort A records before AAAA records.
-.endlist
-
-For example:
-.code
-route_list = domain1  host1:host2:host3  randomize bydns;\
-             domain2  host4:host5
-.endd
-If neither &%byname%& nor &%bydns%& is given, Exim behaves as follows: First, a
-DNS lookup is done. If this yields anything other than HOST_NOT_FOUND, that
-result is used. Otherwise, Exim goes on to try a call to &[getipnodebyname()]&
-or &[gethostbyname()]&, and the result of the lookup is the result of that
-call.
-
-&*Warning*&: It has been discovered that on some systems, if a DNS lookup
-called via &[getipnodebyname()]& times out, HOST_NOT_FOUND is returned
-instead of TRY_AGAIN. That is why the default action is to try a DNS
-lookup first. Only if that gives a definite &"no such host"& is the local
-function called.
-
-&*Compatibility*&: From Exim 4.85 until fixed for 4.90, there was an
-inadvertent constraint that a transport name as an option had to be the last
-option specified.
-
-
-
-If no IP address for a host can be found, what happens is controlled by the
-&%host_find_failed%& option.
-
-.vindex "&$host$&"
-When an address is routed to a local transport, IP addresses are not looked up.
-The host list is passed to the transport in the &$host$& variable.
-
-
-
-.section "Manualroute examples" "SECID123"
-In some of the examples that follow, the presence of the &%remote_smtp%&
-transport, as defined in the default configuration file, is assumed:
-
-.ilist
-.cindex "smart host" "example router"
-The &(manualroute)& router can be used to forward all external mail to a
-&'smart host'&. If you have set up, in the main part of the configuration, a
-named domain list that contains your local domains, for example:
-.code
-domainlist local_domains = my.domain.example
-.endd
-You can arrange for all other domains to be routed to a smart host by making
-your first router something like this:
-.code
-smart_route:
-  driver = manualroute
-  domains = !+local_domains
-  transport = remote_smtp
-  route_list = * smarthost.ref.example
-.endd
-This causes all non-local addresses to be sent to the single host
-&'smarthost.ref.example'&. If a colon-separated list of smart hosts is given,
-they are tried in order
-(but you can use &%hosts_randomize%& to vary the order each time).
-Another way of configuring the same thing is this:
-.code
-smart_route:
-  driver = manualroute
-  transport = remote_smtp
-  route_list = !+local_domains  smarthost.ref.example
-.endd
-There is no difference in behaviour between these two routers as they stand.
-However, they behave differently if &%no_more%& is added to them. In the first
-example, the router is skipped if the domain does not match the &%domains%&
-precondition; the following router is always tried. If the router runs, it
-always matches the domain and so can never decline. Therefore, &%no_more%&
-would have no effect. In the second case, the router is never skipped; it
-always runs. However, if it doesn't match the domain, it declines. In this case
-&%no_more%& would prevent subsequent routers from running.
-
-.next
-.cindex "mail hub example"
-A &'mail hub'& is a host which receives mail for a number of domains via MX
-records in the DNS and delivers it via its own private routing mechanism. Often
-the final destinations are behind a firewall, with the mail hub being the one
-machine that can connect to machines both inside and outside the firewall. The
-&(manualroute)& router is usually used on a mail hub to route incoming messages
-to the correct hosts. For a small number of domains, the routing can be inline,
-using the &%route_list%& option, but for a larger number a file or database
-lookup is easier to manage.
-
-If the domain names are in fact the names of the machines to which the mail is
-to be sent by the mail hub, the configuration can be quite simple. For
-example:
-.code
-hub_route:
-  driver = manualroute
-  transport = remote_smtp
-  route_list = *.rhodes.tvs.example  $domain
-.endd
-This configuration routes domains that match &`*.rhodes.tvs.example`& to hosts
-whose names are the same as the mail domains. A similar approach can be taken
-if the host name can be obtained from the domain name by a string manipulation
-that the expansion facilities can handle. Otherwise, a lookup based on the
-domain can be used to find the host:
-.code
-through_firewall:
-  driver = manualroute
-  transport = remote_smtp
-  route_data = ${lookup {$domain} cdb {/internal/host/routes}}
-.endd
-The result of the lookup must be the name or IP address of the host (or
-hosts) to which the address is to be routed. If the lookup fails, the route
-data is empty, causing the router to decline. The address then passes to the
-next router.
-
-.next
-.cindex "batched SMTP output example"
-.cindex "SMTP" "batched outgoing; example"
-You can use &(manualroute)& to deliver messages to pipes or files in batched
-SMTP format for onward transportation by some other means. This is one way of
-storing mail for a dial-up host when it is not connected. The route list entry
-can be as simple as a single domain name in a configuration like this:
-.code
-save_in_file:
-  driver = manualroute
-  transport = batchsmtp_appendfile
-  route_list = saved.domain.example
-.endd
-though often a pattern is used to pick up more than one domain. If there are
-several domains or groups of domains with different transport requirements,
-different transports can be listed in the routing information:
-.code
-save_in_file:
-  driver = manualroute
-  route_list = \
-    *.saved.domain1.example  $domain  batch_appendfile; \
-    *.saved.domain2.example  \
-      ${lookup{$domain}dbm{/domain2/hosts}{$value}fail} \
-      batch_pipe
-.endd
-.vindex "&$domain$&"
-.vindex "&$host$&"
-The first of these just passes the domain in the &$host$& variable, which
-doesn't achieve much (since it is also in &$domain$&), but the second does a
-file lookup to find a value to pass, causing the router to decline to handle
-the address if the lookup fails.
-
-.next
-.cindex "UUCP" "example of router for"
-Routing mail directly to UUCP software is a specific case of the use of
-&(manualroute)& in a gateway to another mail environment. This is an example of
-one way it can be done:
-.code
-# Transport
-uucp:
-  driver = pipe
-  user = nobody
-  command = /usr/local/bin/uux -r - \
-    ${substr_-5:$host}!rmail ${local_part}
-  return_fail_output = true
-
-# Router
-uucphost:
-  transport = uucp
-  driver = manualroute
-  route_data = \
-    ${lookup{$domain}lsearch{/usr/local/exim/uucphosts}}
-.endd
-The file &_/usr/local/exim/uucphosts_& contains entries like
-.code
-darksite.ethereal.example:           darksite.UUCP
-.endd
-It can be set up more simply without adding and removing &".UUCP"& but this way
-makes clear the distinction between the domain name
-&'darksite.ethereal.example'& and the UUCP host name &'darksite'&.
-.endlist
-.ecindex IIDmanrou1
-.ecindex IIDmanrou2
-
-
-
-
-
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "The queryprogram router" "CHAPdriverlast"
-.scindex IIDquerou1 "&(queryprogram)& router"
-.scindex IIDquerou2 "routers" "&(queryprogram)&"
-.cindex "routing" "by external program"
-The &(queryprogram)& router routes an address by running an external command
-and acting on its output. This is an expensive way to route, and is intended
-mainly for use in lightly-loaded systems, or for performing experiments.
-However, if it is possible to use the precondition options (&%domains%&,
-&%local_parts%&, etc) to skip this router for most addresses, it could sensibly
-be used in special cases, even on a busy host. There are the following private
-options:
-.cindex "options" "&(queryprogram)& router"
-
-.option command queryprogram string&!! unset
-This option must be set. It specifies the command that is to be run. The
-command is split up into a command name and arguments, and then each is
-expanded separately (exactly as for a &(pipe)& transport, described in chapter
-&<<CHAPpipetransport>>&).
-
-
-.option command_group queryprogram string unset
-.cindex "gid (group id)" "in &(queryprogram)& router"
-This option specifies a gid to be set when running the command while routing an
-address for deliver. It must be set if &%command_user%& specifies a numerical
-uid. If it begins with a digit, it is interpreted as the numerical value of the
-gid. Otherwise it is looked up using &[getgrnam()]&.
-
-
-.option command_user queryprogram string unset
-.cindex "uid (user id)" "for &(queryprogram)&"
-This option must be set. It specifies the uid which is set when running the
-command while routing an address for delivery. If the value begins with a digit,
-it is interpreted as the numerical value of the uid. Otherwise, it is looked up
-using &[getpwnam()]& to obtain a value for the uid and, if &%command_group%& is
-not set, a value for the gid also.
-
-&*Warning:*& Changing uid and gid is possible only when Exim is running as
-root, which it does during a normal delivery in a conventional configuration.
-However, when an address is being verified during message reception, Exim is
-usually running as the Exim user, not as root. If the &(queryprogram)& router
-is called from a non-root process, Exim cannot change uid or gid before running
-the command. In this circumstance the command runs under the current uid and
-gid.
-
-
-.option current_directory queryprogram string /
-This option specifies an absolute path which is made the current directory
-before running the command.
-
-
-.option timeout queryprogram time 1h
-If the command does not complete within the timeout period, its process group
-is killed and the message is frozen. A value of zero time specifies no
-timeout.
-
-
-The standard output of the command is connected to a pipe, which is read when
-the command terminates. It should consist of a single line of output,
-containing up to five fields, separated by white space. The maximum length of
-the line is 1023 characters. Longer lines are silently truncated. The first
-field is one of the following words (case-insensitive):
-
-.ilist
-&'Accept'&: routing succeeded; the remaining fields specify what to do (see
-below).
-.next
-&'Decline'&: the router declines; pass the address to the next router, unless
-&%no_more%& is set.
-.next
-&'Fail'&: routing failed; do not pass the address to any more routers. Any
-subsequent text on the line is an error message. If the router is run as part
-of address verification during an incoming SMTP message, the message is
-included in the SMTP response.
-.next
-&'Defer'&: routing could not be completed at this time; try again later. Any
-subsequent text on the line is an error message which is logged. It is not
-included in any SMTP response.
-.next
-&'Freeze'&: the same as &'defer'&, except that the message is frozen.
-.next
-&'Pass'&: pass the address to the next router (or the router specified by
-&%pass_router%&), overriding &%no_more%&.
-.next
-&'Redirect'&: the message is redirected. The remainder of the line is a list of
-new addresses, which are routed independently, starting with the first router,
-or the router specified by &%redirect_router%&, if set.
-.endlist
-
-When the first word is &'accept'&, the remainder of the line consists of a
-number of keyed data values, as follows (split into two lines here, to fit on
-the page):
-.code
-ACCEPT TRANSPORT=<transport> HOSTS=<list of hosts>
-LOOKUP=byname|bydns DATA=<text>
-.endd
-The data items can be given in any order, and all are optional. If no transport
-is included, the transport specified by the generic &%transport%& option is
-used. The list of hosts and the lookup type are needed only if the transport is
-an &(smtp)& transport that does not itself supply a list of hosts.
-
-The format of the list of hosts is the same as for the &(manualroute)& router.
-As well as host names and IP addresses with optional port numbers, as described
-in section &<<SECTformatonehostitem>>&, it may contain names followed by
-&`/MX`& to specify sublists of hosts that are obtained by looking up MX records
-(see section &<<SECThostshowused>>&).
-
-If the lookup type is not specified, Exim behaves as follows when trying to
-find an IP address for each host: First, a DNS lookup is done. If this yields
-anything other than HOST_NOT_FOUND, that result is used. Otherwise, Exim
-goes on to try a call to &[getipnodebyname()]& or &[gethostbyname()]&, and the
-result of the lookup is the result of that call.
-
-.vindex "&$address_data$&"
-If the DATA field is set, its value is placed in the &$address_data$&
-variable. For example, this return line
-.code
-accept hosts=x1.y.example:x2.y.example data="rule1"
-.endd
-routes the address to the default transport, passing a list of two hosts. When
-the transport runs, the string &"rule1"& is in &$address_data$&.
-.ecindex IIDquerou1
-.ecindex IIDquerou2
-
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "The redirect router" "CHAPredirect"
-.scindex IIDredrou1 "&(redirect)& router"
-.scindex IIDredrou2 "routers" "&(redirect)&"
-.cindex "alias file" "in a &(redirect)& router"
-.cindex "address redirection" "&(redirect)& router"
-The &(redirect)& router handles several kinds of address redirection. Its most
-common uses are for resolving local part aliases from a central alias file
-(usually called &_/etc/aliases_&) and for handling users' personal &_.forward_&
-files, but it has many other potential uses. The incoming address can be
-redirected in several different ways:
-
-.ilist
-It can be replaced by one or more new addresses which are themselves routed
-independently.
-.next
-It can be routed to be delivered to a given file or directory.
-.next
-It can be routed to be delivered to a specified pipe command.
-.next
-It can cause an automatic reply to be generated.
-.next
-It can be forced to fail, optionally with a custom error message.
-.next
-It can be temporarily deferred, optionally with a custom message.
-.next
-It can be discarded.
-.endlist
-
-The generic &%transport%& option must not be set for &(redirect)& routers.
-However, there are some private options which define transports for delivery to
-files and pipes, and for generating autoreplies. See the &%file_transport%&,
-&%pipe_transport%& and &%reply_transport%& descriptions below.
-
-If success DSNs have been requested
-.cindex "DSN" "success"
-.cindex "Delivery Status Notification" "success"
-redirection triggers one and the DSN options are not passed any further.
-
-
-
-.section "Redirection data" "SECID124"
-The router operates by interpreting a text string which it obtains either by
-expanding the contents of the &%data%& option, or by reading the entire
-contents of a file whose name is given in the &%file%& option. These two
-options are mutually exclusive. The first is commonly used for handling system
-aliases, in a configuration like this:
-.code
-system_aliases:
-  driver = redirect
-  data = ${lookup{$local_part}lsearch{/etc/aliases}}
-.endd
-If the lookup fails, the expanded string in this example is empty. When the
-expansion of &%data%& results in an empty string, the router declines. A forced
-expansion failure also causes the router to decline; other expansion failures
-cause delivery to be deferred.
-
-A configuration using &%file%& is commonly used for handling users'
-&_.forward_& files, like this:
-.code
-userforward:
-  driver = redirect
-  check_local_user
-  file = $home/.forward
-  no_verify
-.endd
-If the file does not exist, or causes no action to be taken (for example, it is
-empty or consists only of comments), the router declines. &*Warning*&: This
-is not the case when the file contains syntactically valid items that happen to
-yield empty addresses, for example, items containing only RFC 2822 address
-comments.
-
-.new
-.cindex "tainted data" "in filenames"
-.cindex redirect "tainted data"
-Tainted data may not be used for a filename.
-
-&*Warning*&: It is unwise to use &$local_part$& or &$domain$&
-directly for redirection,
-as they are provided by a potential attacker.
-In the examples above, &$local_part$& is used for looking up data held locally
-on the system, and not used directly (the second example derives &$home$& via
-the passsword file or database, using &$local_part$&).
-.wen
-
-
-
-.section "Forward files and address verification" "SECID125"
-.cindex "address redirection" "while verifying"
-It is usual to set &%no_verify%& on &(redirect)& routers which handle users'
-&_.forward_& files, as in the example above. There are two reasons for this:
-
-.ilist
-When Exim is receiving an incoming SMTP message from a remote host, it is
-running under the Exim uid, not as root. Exim is unable to change uid to read
-the file as the user, and it may not be able to read it as the Exim user. So in
-practice the router may not be able to operate.
-.next
-However, even when the router can operate, the existence of a &_.forward_& file
-is unimportant when verifying an address. What should be checked is whether the
-local part is a valid user name or not. Cutting out the redirection processing
-saves some resources.
-.endlist
-
-
-
-
-
-
-.section "Interpreting redirection data" "SECID126"
-.cindex "Sieve filter" "specifying in redirection data"
-.cindex "filter" "specifying in redirection data"
-The contents of the data string, whether obtained from &%data%& or &%file%&,
-can be interpreted in two different ways:
-
-.ilist
-If the &%allow_filter%& option is set true, and the data begins with the text
-&"#Exim filter"& or &"#Sieve filter"&, it is interpreted as a list of
-&'filtering'& instructions in the form of an Exim or Sieve filter file,
-respectively. Details of the syntax and semantics of filter files are described
-in a separate document entitled &'Exim's interfaces to mail filtering'&; this
-document is intended for use by end users.
-.next
-Otherwise, the data must be a comma-separated list of redirection items, as
-described in the next section.
-.endlist
-
-When a message is redirected to a file (a &"mail folder"&), the filename given
-in a non-filter redirection list must always be an absolute path. A filter may
-generate a relative path &-- how this is handled depends on the transport's
-configuration. See section &<<SECTfildiropt>>& for a discussion of this issue
-for the &(appendfile)& transport.
-
-
-
-.section "Items in a non-filter redirection list" "SECTitenonfilred"
-.cindex "address redirection" "non-filter list items"
-When the redirection data is not an Exim or Sieve filter, for example, if it
-comes from a conventional alias or forward file, it consists of a list of
-addresses, filenames, pipe commands, or certain special items (see section
-&<<SECTspecitredli>>& below). The special items can be individually enabled or
-disabled by means of options whose names begin with &%allow_%& or &%forbid_%&,
-depending on their default values. The items in the list are separated by
-commas or newlines.
-If a comma is required in an item, the entire item must be enclosed in double
-quotes.
-
-Lines starting with a # character are comments, and are ignored, and # may
-also appear following a comma, in which case everything between the # and the
-next newline character is ignored.
-
-If an item is entirely enclosed in double quotes, these are removed. Otherwise
-double quotes are retained because some forms of mail address require their use
-(but never to enclose the entire address). In the following description,
-&"item"& refers to what remains after any surrounding double quotes have been
-removed.
-
-.vindex "&$local_part$&"
-&*Warning*&: If you use an Exim expansion to construct a redirection address,
-and the expansion contains a reference to &$local_part$&, you should make use
-of the &%quote_local_part%& expansion operator, in case the local part contains
-special characters. For example, to redirect all mail for the domain
-&'obsolete.example'&, retaining the existing local part, you could use this
-setting:
-.code
-data = ${quote_local_part:$local_part}@newdomain.example
-.endd
-
-
-.section "Redirecting to a local mailbox" "SECTredlocmai"
-.cindex "routing" "loops in"
-.cindex "loop" "while routing, avoidance of"
-.cindex "address redirection" "to local mailbox"
-A redirection item may safely be the same as the address currently under
-consideration. This does not cause a routing loop, because a router is
-automatically skipped if any ancestor of the address that is being processed
-is the same as the current address and was processed by the current router.
-Such an address is therefore passed to the following routers, so it is handled
-as if there were no redirection. When making this loop-avoidance test, the
-complete local part, including any prefix or suffix, is used.
-
-.cindex "address redirection" "local part without domain"
-Specifying the same local part without a domain is a common usage in personal
-filter files when the user wants to have messages delivered to the local
-mailbox and also forwarded elsewhere. For example, the user whose login is
-&'cleo'& might have a &_.forward_& file containing this:
-.code
-cleo, cleopatra@egypt.example
-.endd
-.cindex "backslash in alias file"
-.cindex "alias file" "backslash in"
-For compatibility with other MTAs, such unqualified local parts may be
-preceded by &"\"&, but this is not a requirement for loop prevention. However,
-it does make a difference if more than one domain is being handled
-synonymously.
-
-If an item begins with &"\"& and the rest of the item parses as a valid RFC
-2822 address that does not include a domain, the item is qualified using the
-domain of the incoming address. In the absence of a leading &"\"&, unqualified
-addresses are qualified using the value in &%qualify_recipient%&, but you can
-force the incoming domain to be used by setting &%qualify_preserve_domain%&.
-
-Care must be taken if there are alias names for local users.
-Consider an MTA handling a single local domain where the system alias file
-contains:
-.code
-Sam.Reman: spqr
-.endd
-Now suppose that Sam (whose login id is &'spqr'&) wants to save copies of
-messages in the local mailbox, and also forward copies elsewhere. He creates
-this forward file:
-.code
-Sam.Reman, spqr@reme.elsewhere.example
-.endd
-With these settings, an incoming message addressed to &'Sam.Reman'& fails. The
-&(redirect)& router for system aliases does not process &'Sam.Reman'& the
-second time round, because it has previously routed it,
-and the following routers presumably cannot handle the alias. The forward file
-should really contain
-.code
-spqr, spqr@reme.elsewhere.example
-.endd
-but because this is such a common error, the &%check_ancestor%& option (see
-below) exists to provide a way to get round it. This is normally set on a
-&(redirect)& router that is handling users' &_.forward_& files.
-
-
-
-.section "Special items in redirection lists" "SECTspecitredli"
-In addition to addresses, the following types of item may appear in redirection
-lists (that is, in non-filter redirection data):
-
-.ilist
-.cindex "pipe" "in redirection list"
-.cindex "address redirection" "to pipe"
-An item is treated as a pipe command if it begins with &"|"& and does not parse
-as a valid RFC 2822 address that includes a domain. A transport for running the
-command must be specified by the &%pipe_transport%& option.
-Normally, either the router or the transport specifies a user and a group under
-which to run the delivery. The default is to use the Exim user and group.
-
-Single or double quotes can be used for enclosing the individual arguments of
-the pipe command; no interpretation of escapes is done for single quotes. If
-the command contains a comma character, it is necessary to put the whole item
-in double quotes, for example:
-.code
-"|/some/command ready,steady,go"
-.endd
-since items in redirection lists are terminated by commas. Do not, however,
-quote just the command. An item such as
-.code
-|"/some/command ready,steady,go"
-.endd
-is interpreted as a pipe with a rather strange command name, and no arguments.
-
-Note that the above example assumes that the text comes from a lookup source
-of some sort, so that the quotes are part of the data.  If composing a
-redirect router with a &%data%& option directly specifying this command, the
-quotes will be used by the configuration parser to define the extent of one
-string, but will not be passed down into the redirect router itself.  There
-are two main approaches to get around this: escape quotes to be part of the
-data itself, or avoid using this mechanism and instead create a custom
-transport with the &%command%& option set and reference that transport from
-an &%accept%& router.
-
-.next
-.cindex "file" "in redirection list"
-.cindex "address redirection" "to file"
-An item is interpreted as a path name if it begins with &"/"& and does not
-parse as a valid RFC 2822 address that includes a domain. For example,
-.code
-/home/world/minbari
-.endd
-is treated as a filename, but
-.code
-/s=molari/o=babylon/@x400gate.way
-.endd
-is treated as an address. For a filename, a transport must be specified using
-the &%file_transport%& option. However, if the generated path name ends with a
-forward slash character, it is interpreted as a directory name rather than a
-filename, and &%directory_transport%& is used instead.
-
-Normally, either the router or the transport specifies a user and a group under
-which to run the delivery. The default is to use the Exim user and group.
-
-.cindex "&_/dev/null_&"
-However, if a redirection item is the path &_/dev/null_&, delivery to it is
-bypassed at a high level, and the log entry shows &"**bypassed**"&
-instead of a transport name. In this case the user and group are not used.
-
-.next
-.cindex "included address list"
-.cindex "address redirection" "included external list"
-If an item is of the form
-.code
-:include:<path name>
-.endd
-a list of further items is taken from the given file and included at that
-point. &*Note*&: Such a file can not be a filter file; it is just an
-out-of-line addition to the list. The items in the included list are separated
-by commas or newlines and are not subject to expansion. If this is the first
-item in an alias list in an &(lsearch)& file, a colon must be used to terminate
-the alias name. This example is incorrect:
-.code
-list1    :include:/opt/lists/list1
-.endd
-It must be given as
-.code
-list1:   :include:/opt/lists/list1
-.endd
-.new
-.cindex "tainted data" "in filenames"
-.cindex redirect "tainted data"
-Tainted data may not be used for a filename.
-.wen
-.next
-.cindex "address redirection" "to black hole"
-.cindex "delivery" "discard"
-.cindex "delivery" "blackhole"
-.cindex "black hole"
-.cindex "abandoning mail"
-Sometimes you want to throw away mail to a particular local part.  Making the
-&%data%& option expand to an empty string does not work, because that causes
-the router to decline. Instead, the alias item
-.code
-:blackhole:
-.endd
-can be used. It does what its name implies. No delivery is
-done, and no error message is generated. This has the same effect as specifying
-&_/dev/null_& as a destination, but it can be independently disabled.
-
-&*Warning*&: If &':blackhole:'& appears anywhere in a redirection list, no
-delivery is done for the original local part, even if other redirection items
-are present. If you are generating a multi-item list (for example, by reading a
-database) and need the ability to provide a no-op item, you must use
-&_/dev/null_&.
-
-.next
-.cindex "delivery" "forcing failure"
-.cindex "delivery" "forcing deferral"
-.cindex "failing delivery" "forcing"
-.cindex "deferred delivery, forcing"
-.cindex "customizing" "failure message"
-An attempt to deliver a particular address can be deferred or forced to fail by
-redirection items of the form
-.code
-:defer:
-:fail:
-.endd
-respectively. When a redirection list contains such an item, it applies
-to the entire redirection; any other items in the list are ignored. Any
-text following &':fail:'& or &':defer:'& is placed in the error text
-associated with the failure. For example, an alias file might contain:
-.code
-X.Employee:  :fail: Gone away, no forwarding address
-.endd
-In the case of an address that is being verified from an ACL or as the subject
-of a
-.cindex "VRFY" "error text, display of"
-VRFY command, the text is included in the SMTP error response by
-default.
-.cindex "EXPN" "error text, display of"
-The text is not included in the response to an EXPN command. In non-SMTP cases
-the text is included in the error message that Exim generates.
-
-.cindex "SMTP" "error codes"
-By default, Exim sends a 451 SMTP code for a &':defer:'&, and 550 for
-&':fail:'&. However, if the message starts with three digits followed by a
-space, optionally followed by an extended code of the form &'n.n.n'&, also
-followed by a space, and the very first digit is the same as the default error
-code, the code from the message is used instead. If the very first digit is
-incorrect, a panic error is logged, and the default code is used. You can
-suppress the use of the supplied code in a redirect router by setting the
-&%forbid_smtp_code%& option true. In this case, any SMTP code is quietly
-ignored.
-
-.vindex "&$acl_verify_message$&"
-In an ACL, an explicitly provided message overrides the default, but the
-default message is available in the variable &$acl_verify_message$& and can
-therefore be included in a custom message if this is desired.
-
-Normally the error text is the rest of the redirection list &-- a comma does
-not terminate it &-- but a newline does act as a terminator. Newlines are not
-normally present in alias expansions. In &(lsearch)& lookups they are removed
-as part of the continuation process, but they may exist in other kinds of
-lookup and in &':include:'& files.
-
-During routing for message delivery (as opposed to verification), a redirection
-containing &':fail:'& causes an immediate failure of the incoming address,
-whereas &':defer:'& causes the message to remain in the queue so that a
-subsequent delivery attempt can happen at a later time. If an address is
-deferred for too long, it will ultimately fail, because the normal retry
-rules still apply.
-
-.next
-.cindex "alias file" "exception to default"
-Sometimes it is useful to use a single-key search type with a default (see
-chapter &<<CHAPfdlookup>>&) to look up aliases. However, there may be a need
-for exceptions to the default. These can be handled by aliasing them to
-&':unknown:'&. This differs from &':fail:'& in that it causes the &(redirect)&
-router to decline, whereas &':fail:'& forces routing to fail. A lookup which
-results in an empty redirection list has the same effect.
-.endlist
-
-
-.section "Duplicate addresses" "SECTdupaddr"
-.cindex "duplicate addresses"
-.cindex "address duplicate, discarding"
-.cindex "pipe" "duplicated"
-Exim removes duplicate addresses from the list to which it is delivering, so as
-to deliver just one copy to each address. This does not apply to deliveries
-routed to pipes by different immediate parent addresses, but an indirect
-aliasing scheme of the type
-.code
-pipe:       |/some/command $local_part
-localpart1: pipe
-localpart2: pipe
-.endd
-does not work with a message that is addressed to both local parts, because
-when the second is aliased to the intermediate local part &"pipe"& it gets
-discarded as being the same as a previously handled address. However, a scheme
-such as
-.code
-localpart1: |/some/command $local_part
-localpart2: |/some/command $local_part
-.endd
-does result in two different pipe deliveries, because the immediate parents of
-the pipes are distinct.
-
-
-
-.section "Repeated redirection expansion" "SECID128"
-.cindex "repeated redirection expansion"
-.cindex "address redirection" "repeated for each delivery attempt"
-When a message cannot be delivered to all of its recipients immediately,
-leading to two or more delivery attempts, redirection expansion is carried out
-afresh each time for those addresses whose children were not all previously
-delivered. If redirection is being used as a mailing list, this can lead to new
-members of the list receiving copies of old messages. The &%one_time%& option
-can be used to avoid this.
-
-
-.section "Errors in redirection lists" "SECID129"
-.cindex "address redirection" "errors"
-If &%skip_syntax_errors%& is set, a malformed address that causes a parsing
-error is skipped, and an entry is written to the main log. This may be useful
-for mailing lists that are automatically managed. Otherwise, if an error is
-detected while generating the list of new addresses, the original address is
-deferred. See also &%syntax_errors_to%&.
-
-
-
-.section "Private options for the redirect router" "SECID130"
-
-.cindex "options" "&(redirect)& router"
-The private options for the &(redirect)& router are as follows:
-
-
-.option allow_defer redirect boolean false
-Setting this option allows the use of &':defer:'& in non-filter redirection
-data, or the &%defer%& command in an Exim filter file.
-
-
-.option allow_fail redirect boolean false
-.cindex "failing delivery" "from filter"
-If this option is true, the &':fail:'& item can be used in a redirection list,
-and the &%fail%& command may be used in an Exim filter file.
-
-
-.option allow_filter redirect boolean false
-.cindex "filter" "enabling use of"
-.cindex "Sieve filter" "enabling use of"
-Setting this option allows Exim to interpret redirection data that starts with
-&"#Exim filter"& or &"#Sieve filter"& as a set of filtering instructions. There
-are some features of Exim filter files that some administrators may wish to
-lock out; see the &%forbid_filter_%&&'xxx'& options below.
-
-It is also possible to lock out Exim filters or Sieve filters while allowing
-the other type; see &%forbid_exim_filter%& and &%forbid_sieve_filter%&.
-
-
-The filter is run using the uid and gid set by the generic &%user%& and
-&%group%& options. These take their defaults from the password data if
-&%check_local_user%& is set, so in the normal case of users' personal filter
-files, the filter is run as the relevant user. When &%allow_filter%& is set
-true, Exim insists that either &%check_local_user%& or &%user%& is set.
-
-
-
-.option allow_freeze redirect boolean false
-.cindex "freezing messages" "allowing in filter"
-Setting this option allows the use of the &%freeze%& command in an Exim filter.
-This command is more normally encountered in system filters, and is disabled by
-default for redirection filters because it isn't something you usually want to
-let ordinary users do.
-
-
-
-.option check_ancestor redirect boolean false
-This option is concerned with handling generated addresses that are the same
-as some address in the list of redirection ancestors of the current address.
-Although it is turned off by default in the code, it is set in the default
-configuration file for handling users' &_.forward_& files. It is recommended
-for this use of the &(redirect)& router.
-
-When &%check_ancestor%& is set, if a generated address (including the domain)
-is the same as any ancestor of the current address, it is replaced by a copy of
-the current address. This helps in the case where local part A is aliased to B,
-and B has a &_.forward_& file pointing back to A. For example, within a single
-domain, the local part &"Joe.Bloggs"& is aliased to &"jb"& and
-&_&~jb/.forward_& contains:
-.code
-\Joe.Bloggs, <other item(s)>
-.endd
-Without the &%check_ancestor%& setting, either local part (&"jb"& or
-&"joe.bloggs"&) gets processed once by each router and so ends up as it was
-originally. If &"jb"& is the real mailbox name, mail to &"jb"& gets delivered
-(having been turned into &"joe.bloggs"& by the &_.forward_& file and back to
-&"jb"& by the alias), but mail to &"joe.bloggs"& fails. Setting
-&%check_ancestor%& on the &(redirect)& router that handles the &_.forward_&
-file prevents it from turning &"jb"& back into &"joe.bloggs"& when that was the
-original address. See also the &%repeat_use%& option below.
-
-
-.option check_group redirect boolean "see below"
-When the &%file%& option is used, the group owner of the file is checked only
-when this option is set. The permitted groups are those listed in the
-&%owngroups%& option, together with the user's default group if
-&%check_local_user%& is set. If the file has the wrong group, routing is
-deferred. The default setting for this option is true if &%check_local_user%&
-is set and the &%modemask%& option permits the group write bit, or if the
-&%owngroups%& option is set. Otherwise it is false, and no group check occurs.
-
-
-
-.option check_owner redirect boolean "see below"
-When the &%file%& option is used, the owner of the file is checked only when
-this option is set. If &%check_local_user%& is set, the local user is
-permitted; otherwise the owner must be one of those listed in the &%owners%&
-option. The default value for this option is true if &%check_local_user%& or
-&%owners%& is set. Otherwise the default is false, and no owner check occurs.
-
-
-.option data redirect string&!! unset
-This option is mutually exclusive with &%file%&. One or other of them must be
-set, but not both. The contents of &%data%& are expanded, and then used as the
-list of forwarding items, or as a set of filtering instructions. If the
-expansion is forced to fail, or the result is an empty string or a string that
-has no effect (consists entirely of comments), the router declines.
-
-When filtering instructions are used, the string must begin with &"#Exim
-filter"&, and all comments in the string, including this initial one, must be
-terminated with newline characters. For example:
-.code
-data = #Exim filter\n\
-       if $h_to: contains Exim then save $home/mail/exim endif
-.endd
-If you are reading the data from a database where newlines cannot be included,
-you can use the &${sg}$& expansion item to turn the escape string of your
-choice into a newline.
-
-
-.option directory_transport redirect string&!! unset
-A &(redirect)& router sets up a direct delivery to a directory when a path name
-ending with a slash is specified as a new &"address"&. The transport used is
-specified by this option, which, after expansion, must be the name of a
-configured transport. This should normally be an &(appendfile)& transport.
-
-
-.option file redirect string&!! unset
-This option specifies the name of a file that contains the redirection data. It
-is mutually exclusive with the &%data%& option. The string is expanded before
-use; if the expansion is forced to fail, the router declines. Other expansion
-failures cause delivery to be deferred. The result of a successful expansion
-must be an absolute path. The entire file is read and used as the redirection
-data. If the data is an empty string or a string that has no effect (consists
-entirely of comments), the router declines.
-
-.cindex "NFS" "checking for file existence"
-If the attempt to open the file fails with a &"does not exist"& error, Exim
-runs a check on the containing directory,
-unless &%ignore_enotdir%& is true (see below).
-If the directory does not appear to exist, delivery is deferred. This can
-happen when users' &_.forward_& files are in NFS-mounted directories, and there
-is a mount problem. If the containing directory does exist, but the file does
-not, the router declines.
-
-
-.option file_transport redirect string&!! unset
-.vindex "&$address_file$&"
-A &(redirect)& router sets up a direct delivery to a file when a path name not
-ending in a slash is specified as a new &"address"&. The transport used is
-specified by this option, which, after expansion, must be the name of a
-configured transport. This should normally be an &(appendfile)& transport. When
-it is running, the filename is in &$address_file$&.
-
-
-.option filter_prepend_home redirect boolean true
-When this option is true, if a &(save)& command in an Exim filter specifies a
-relative path, and &$home$& is defined, it is automatically prepended to the
-relative path. If this option is set false, this action does not happen. The
-relative path is then passed to the transport unmodified.
-
-
-.option forbid_blackhole redirect boolean false
-.cindex "restricting access to features"
-.cindex "filter" "locking out certain features"
-If this option is true, the &':blackhole:'& item may not appear in a
-redirection list.
-
-
-.option forbid_exim_filter redirect boolean false
-.cindex "restricting access to features"
-.cindex "filter" "locking out certain features"
-If this option is set true, only Sieve filters are permitted when
-&%allow_filter%& is true.
-
-
-
-
-.option forbid_file redirect boolean false
-.cindex "restricting access to features"
-.cindex "delivery" "to file; forbidding"
-.cindex "filter" "locking out certain features"
-.cindex "Sieve filter" "forbidding delivery to a file"
-.cindex "Sieve filter" "&""keep""& facility; disabling"
-If this option is true, this router may not generate a new address that
-specifies delivery to a local file or directory, either from a filter or from a
-conventional forward file. This option is forced to be true if &%one_time%& is
-set. It applies to Sieve filters as well as to Exim filters, but if true, it
-locks out the Sieve's &"keep"& facility.
-
-
-.option forbid_filter_dlfunc redirect boolean false
-.cindex "restricting access to features"
-.cindex "filter" "locking out certain features"
-If this option is true, string expansions in Exim filters are not allowed to
-make use of the &%dlfunc%& expansion facility to run dynamically loaded
-functions.
-
-.option forbid_filter_existstest redirect boolean false
-.cindex "restricting access to features"
-.cindex "filter" "locking out certain features"
-.cindex "expansion" "statting a file"
-If this option is true, string expansions in Exim filters are not allowed to
-make use of the &%exists%& condition or the &%stat%& expansion item.
-
-.option forbid_filter_logwrite redirect boolean false
-.cindex "restricting access to features"
-.cindex "filter" "locking out certain features"
-If this option is true, use of the logging facility in Exim filters is not
-permitted. Logging is in any case available only if the filter is being run
-under some unprivileged uid (which is normally the case for ordinary users'
-&_.forward_& files).
-
-
-.option forbid_filter_lookup redirect boolean false
-.cindex "restricting access to features"
-.cindex "filter" "locking out certain features"
-If this option is true, string expansions in Exim filter files are not allowed
-to make use of &%lookup%& items.
-
-
-.option forbid_filter_perl redirect boolean false
-.cindex "restricting access to features"
-.cindex "filter" "locking out certain features"
-This option has an effect only if Exim is built with embedded Perl support. If
-it is true, string expansions in Exim filter files are not allowed to make use
-of the embedded Perl support.
-
-
-.option forbid_filter_readfile redirect boolean false
-.cindex "restricting access to features"
-.cindex "filter" "locking out certain features"
-If this option is true, string expansions in Exim filter files are not allowed
-to make use of &%readfile%& items.
-
-
-.option forbid_filter_readsocket redirect boolean false
-.cindex "restricting access to features"
-.cindex "filter" "locking out certain features"
-If this option is true, string expansions in Exim filter files are not allowed
-to make use of &%readsocket%& items.
-
-
-.option forbid_filter_reply redirect boolean false
-.cindex "restricting access to features"
-.cindex "filter" "locking out certain features"
-If this option is true, this router may not generate an automatic reply
-message. Automatic replies can be generated only from Exim or Sieve filter
-files, not from traditional forward files. This option is forced to be true if
-&%one_time%& is set.
-
-
-.option forbid_filter_run redirect boolean false
-.cindex "restricting access to features"
-.cindex "filter" "locking out certain features"
-If this option is true, string expansions in Exim filter files are not allowed
-to make use of &%run%& items.
-
-
-.option forbid_include redirect boolean false
-.cindex "restricting access to features"
-.cindex "filter" "locking out certain features"
-If this option is true, items of the form
-.code
-:include:<path name>
-.endd
-are not permitted in non-filter redirection lists.
-
-
-.option forbid_pipe redirect boolean false
-.cindex "restricting access to features"
-.cindex "filter" "locking out certain features"
-.cindex "delivery" "to pipe; forbidding"
-If this option is true, this router may not generate a new address which
-specifies delivery to a pipe, either from an Exim filter or from a conventional
-forward file. This option is forced to be true if &%one_time%& is set.
-
-
-.option forbid_sieve_filter redirect boolean false
-.cindex "restricting access to features"
-.cindex "filter" "locking out certain features"
-If this option is set true, only Exim filters are permitted when
-&%allow_filter%& is true.
-
-
-.cindex "SMTP" "error codes"
-.option forbid_smtp_code redirect boolean false
-If this option is set true, any SMTP error codes that are present at the start
-of messages specified for &`:defer:`& or &`:fail:`& are quietly ignored, and
-the default codes (451 and 550, respectively) are always used.
-
-
-
-
-.option hide_child_in_errmsg redirect boolean false
-.cindex "bounce message" "redirection details; suppressing"
-If this option is true, it prevents Exim from quoting a child address if it
-generates a bounce or delay message for it. Instead it says &"an address
-generated from <&'the top level address'&>"&. Of course, this applies only to
-bounces generated locally. If a message is forwarded to another host, &'its'&
-bounce may well quote the generated address.
-
-
-.option ignore_eacces redirect boolean false
-.cindex "EACCES"
-If this option is set and an attempt to open a redirection file yields the
-EACCES error (permission denied), the &(redirect)& router behaves as if the
-file did not exist.
-
-
-.option ignore_enotdir redirect boolean false
-.cindex "ENOTDIR"
-If this option is set and an attempt to open a redirection file yields the
-ENOTDIR error (something on the path is not a directory), the &(redirect)&
-router behaves as if the file did not exist.
-
-Setting &%ignore_enotdir%& has another effect as well: When a &(redirect)&
-router that has the &%file%& option set discovers that the file does not exist
-(the ENOENT error), it tries to &[stat()]& the parent directory, as a check
-against unmounted NFS directories. If the parent can not be statted, delivery
-is deferred. However, it seems wrong to do this check when &%ignore_enotdir%&
-is set, because that option tells Exim to ignore &"something on the path is not
-a directory"& (the ENOTDIR error). This is a confusing area, because it seems
-that some operating systems give ENOENT where others give ENOTDIR.
-
-
-
-.option include_directory redirect string unset
-If this option is set, the path names of any &':include:'& items in a
-redirection list must start with this directory.
-
-
-.option modemask redirect "octal integer" 022
-This specifies mode bits which must not be set for a file specified by the
-&%file%& option. If any of the forbidden bits are set, delivery is deferred.
-
-
-.option one_time redirect boolean false
-.cindex "one-time aliasing/forwarding expansion"
-.cindex "alias file" "one-time expansion"
-.cindex "forward file" "one-time expansion"
-.cindex "mailing lists" "one-time expansion"
-.cindex "address redirection" "one-time expansion"
-Sometimes the fact that Exim re-evaluates aliases and reprocesses redirection
-files each time it tries to deliver a message causes a problem when one or more
-of the generated addresses fails be delivered at the first attempt. The problem
-is not one of duplicate delivery &-- Exim is clever enough to handle that &--
-but of what happens when the redirection list changes during the time that the
-message is on Exim's queue. This is particularly true in the case of mailing
-lists, where new subscribers might receive copies of messages that were posted
-before they subscribed.
-
-If &%one_time%& is set and any addresses generated by the router fail to
-deliver at the first attempt, the failing addresses are added to the message as
-&"top level"& addresses, and the parent address that generated them is marked
-&"delivered"&. Thus, redirection does not happen again at the next delivery
-attempt.
-
-&*Warning 1*&: Any header line addition or removal that is specified by this
-router would be lost if delivery did not succeed at the first attempt. For this
-reason, the &%headers_add%& and &%headers_remove%& generic options are not
-permitted when &%one_time%& is set.
-
-&*Warning 2*&: To ensure that the router generates only addresses (as opposed
-to pipe or file deliveries or auto-replies) &%forbid_file%&, &%forbid_pipe%&,
-and &%forbid_filter_reply%& are forced to be true when &%one_time%& is set.
-
-&*Warning 3*&: The &%unseen%& generic router option may not be set with
-&%one_time%&.
-
-The original top-level address is remembered with each of the generated
-addresses, and is output in any log messages. However, any intermediate parent
-addresses are not recorded. This makes a difference to the log only if
-&%all_parents%& log selector is set. It is expected that &%one_time%& will
-typically be used for mailing lists, where there is normally just one level of
-expansion.
-
-
-.option owners redirect "string list" unset
-.cindex "ownership" "alias file"
-.cindex "ownership" "forward file"
-.cindex "alias file" "ownership"
-.cindex "forward file" "ownership"
-This specifies a list of permitted owners for the file specified by &%file%&.
-This list is in addition to the local user when &%check_local_user%& is set.
-See &%check_owner%& above.
-
-
-.option owngroups redirect "string list" unset
-This specifies a list of permitted groups for the file specified by &%file%&.
-The list is in addition to the local user's primary group when
-&%check_local_user%& is set. See &%check_group%& above.
-
-
-.option pipe_transport redirect string&!! unset
-.vindex "&$address_pipe$&"
-A &(redirect)& router sets up a direct delivery to a pipe when a string
-starting with a vertical bar character is specified as a new &"address"&. The
-transport used is specified by this option, which, after expansion, must be the
-name of a configured transport. This should normally be a &(pipe)& transport.
-When the transport is run, the pipe command is in &$address_pipe$&.
-
-
-.option qualify_domain redirect string&!! unset
-.vindex "&$qualify_recipient$&"
-If this option is set, and an unqualified address (one without a domain) is
-generated, and that address would normally be qualified by the global setting
-in &%qualify_recipient%&, it is instead qualified with the domain specified by
-expanding this string. If the expansion fails, the router declines. If you want
-to revert to the default, you can have the expansion generate
-&$qualify_recipient$&.
-
-This option applies to all unqualified addresses generated by Exim filters,
-but for traditional &_.forward_& files, it applies only to addresses that are
-not preceded by a backslash. Sieve filters cannot generate unqualified
-addresses.
-
-.option qualify_preserve_domain redirect boolean false
-.cindex "domain" "in redirection; preserving"
-.cindex "preserving domain in redirection"
-.cindex "address redirection" "domain; preserving"
-If this option is set, the router's local &%qualify_domain%& option must not be
-set (a configuration error occurs if it is). If an unqualified address (one
-without a domain) is generated, it is qualified with the domain of the parent
-address (the immediately preceding ancestor) instead of the global
-&%qualify_recipient%& value. In the case of a traditional &_.forward_& file,
-this applies whether or not the address is preceded by a backslash.
-
-
-.option repeat_use redirect boolean true
-If this option is set false, the router is skipped for a child address that has
-any ancestor that was routed by this router. This test happens before any of
-the other preconditions are tested. Exim's default anti-looping rules skip
-only when the ancestor is the same as the current address. See also
-&%check_ancestor%& above and the generic &%redirect_router%& option.
-
-
-.option reply_transport redirect string&!! unset
-A &(redirect)& router sets up an automatic reply when a &%mail%& or
-&%vacation%& command is used in a filter file. The transport used is specified
-by this option, which, after expansion, must be the name of a configured
-transport. This should normally be an &(autoreply)& transport. Other transports
-are unlikely to do anything sensible or useful.
-
-
-.option rewrite redirect boolean true
-.cindex "address redirection" "disabling rewriting"
-If this option is set false, addresses generated by the router are not
-subject to address rewriting. Otherwise, they are treated like new addresses
-and are rewritten according to the global rewriting rules.
-
-
-.option sieve_subaddress redirect string&!! unset
-The value of this option is passed to a Sieve filter to specify the
-:subaddress part of an address.
-
-.option sieve_useraddress redirect string&!! unset
-The value of this option is passed to a Sieve filter to specify the :user part
-of an address. However, if it is unset, the entire original local part
-(including any prefix or suffix) is used for :user.
-
-
-.option sieve_vacation_directory redirect string&!! unset
-.cindex "Sieve filter" "vacation directory"
-To enable the &"vacation"& extension for Sieve filters, you must set
-&%sieve_vacation_directory%& to the directory where vacation databases are held
-(do not put anything else in that directory), and ensure that the
-&%reply_transport%& option refers to an &(autoreply)& transport. Each user
-needs their own directory; Exim will create it if necessary.
-
-
-
-.option skip_syntax_errors redirect boolean false
-.cindex "forward file" "broken"
-.cindex "address redirection" "broken files"
-.cindex "alias file" "broken"
-.cindex "broken alias or forward files"
-.cindex "ignoring faulty addresses"
-.cindex "skipping faulty addresses"
-.cindex "error" "skipping bad syntax"
-If &%skip_syntax_errors%& is set, syntactically malformed addresses in
-non-filter redirection data are skipped, and each failing address is logged. If
-&%syntax_errors_to%& is set, a message is sent to the address it defines,
-giving details of the failures. If &%syntax_errors_text%& is set, its contents
-are expanded and placed at the head of the error message generated by
-&%syntax_errors_to%&. Usually it is appropriate to set &%syntax_errors_to%& to
-be the same address as the generic &%errors_to%& option. The
-&%skip_syntax_errors%& option is often used when handling mailing lists.
-
-If all the addresses in a redirection list are skipped because of syntax
-errors, the router declines to handle the original address, and it is passed to
-the following routers.
-
-If &%skip_syntax_errors%& is set when an Exim filter is interpreted, any syntax
-error in the filter causes filtering to be abandoned without any action being
-taken. The incident is logged, and the router declines to handle the address,
-so it is passed to the following routers.
-
-.cindex "Sieve filter" "syntax errors in"
-Syntax errors in a Sieve filter file cause the &"keep"& action to occur. This
-action is specified by RFC 3028. The values of &%skip_syntax_errors%&,
-&%syntax_errors_to%&, and &%syntax_errors_text%& are not used.
-
-&%skip_syntax_errors%& can be used to specify that errors in users' forward
-lists or filter files should not prevent delivery. The &%syntax_errors_to%&
-option, used with an address that does not get redirected, can be used to
-notify users of these errors, by means of a router like this:
-.code
-userforward:
-  driver = redirect
-  allow_filter
-  check_local_user
-  file = $home/.forward
-  file_transport = address_file
-  pipe_transport = address_pipe
-  reply_transport = address_reply
-  no_verify
-  skip_syntax_errors
-  syntax_errors_to = real-$local_part@$domain
-  syntax_errors_text = \
-   This is an automatically generated message. An error has\n\
-   been found in your .forward file. Details of the error are\n\
-   reported below. While this error persists, you will receive\n\
-   a copy of this message for every message that is addressed\n\
-   to you. If your .forward file is a filter file, or if it is\n\
-   a non-filter file containing no valid forwarding addresses,\n\
-   a copy of each incoming message will be put in your normal\n\
-   mailbox. If a non-filter file contains at least one valid\n\
-   forwarding address, forwarding to the valid addresses will\n\
-   happen, and those will be the only deliveries that occur.
-.endd
-You also need a router to ensure that local addresses that are prefixed by
-&`real-`& are recognized, but not forwarded or filtered. For example, you could
-put this immediately before the &(userforward)& router:
-.code
-real_localuser:
-  driver = accept
-  check_local_user
-  local_part_prefix = real-
-  transport = local_delivery
-.endd
-For security, it would probably be a good idea to restrict the use of this
-router to locally-generated messages, using a condition such as this:
-.code
-  condition = ${if match {$sender_host_address}\
-                         {\N^(|127\.0\.0\.1)$\N}}
-.endd
-
-
-.option syntax_errors_text redirect string&!! unset
-See &%skip_syntax_errors%& above.
-
-
-.option syntax_errors_to redirect string unset
-See &%skip_syntax_errors%& above.
-.ecindex IIDredrou1
-.ecindex IIDredrou2
-
-
-
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "Environment for running local transports" "CHAPenvironment" &&&
-         "Environment for local transports"
-.scindex IIDenvlotra1 "local transports" "environment for"
-.scindex IIDenvlotra2 "environment" "local transports"
-.scindex IIDenvlotra3 "transport" "local; environment for"
-Local transports handle deliveries to files and pipes. (The &(autoreply)&
-transport can be thought of as similar to a pipe.) Exim always runs transports
-in subprocesses, under specified uids and gids. Typical deliveries to local
-mailboxes run under the uid and gid of the local user.
-
-Exim also sets a specific current directory while running the transport; for
-some transports a home directory setting is also relevant. The &(pipe)&
-transport is the only one that sets up environment variables; see section
-&<<SECTpipeenv>>& for details.
-
-The values used for the uid, gid, and the directories may come from several
-different places. In many cases, the router that handles the address associates
-settings with that address as a result of its &%check_local_user%&, &%group%&,
-or &%user%& options. However, values may also be given in the transport's own
-configuration, and these override anything that comes from the router.
-
-
-
-.section "Concurrent deliveries" "SECID131"
-.cindex "concurrent deliveries"
-.cindex "simultaneous deliveries"
-If two different messages for the same local recipient arrive more or less
-simultaneously, the two delivery processes are likely to run concurrently. When
-the &(appendfile)& transport is used to write to a file, Exim applies locking
-rules to stop concurrent processes from writing to the same file at the same
-time.
-
-However, when you use a &(pipe)& transport, it is up to you to arrange any
-locking that is needed. Here is a silly example:
-.code
-my_transport:
-  driver = pipe
-  command = /bin/sh -c 'cat >>/some/file'
-.endd
-This is supposed to write the message at the end of the file. However, if two
-messages arrive at the same time, the file will be scrambled. You can use the
-&%exim_lock%& utility program (see section &<<SECTmailboxmaint>>&) to lock a
-file using the same algorithm that Exim itself uses.
-
-
-
-
-.section "Uids and gids" "SECTenvuidgid"
-.cindex "local transports" "uid and gid"
-.cindex "transport" "local; uid and gid"
-All transports have the options &%group%& and &%user%&. If &%group%& is set, it
-overrides any group that the router set in the address, even if &%user%& is not
-set for the transport. This makes it possible, for example, to run local mail
-delivery under the uid of the recipient (set by the router), but in a special
-group (set by the transport). For example:
-.code
-# Routers ...
-# User/group are set by check_local_user in this router
-local_users:
-  driver = accept
-  check_local_user
-  transport = group_delivery
-
-# Transports ...
-# This transport overrides the group
-group_delivery:
-  driver = appendfile
-  file = /var/spool/mail/$local_part
-  group = mail
-.endd
-If &%user%& is set for a transport, its value overrides what is set in the
-address by the router. If &%user%& is non-numeric and &%group%& is not set, the
-gid associated with the user is used. If &%user%& is numeric, &%group%& must be
-set.
-
-.oindex "&%initgroups%&"
-When the uid is taken from the transport's configuration, the &[initgroups()]&
-function is called for the groups associated with that uid if the
-&%initgroups%& option is set for the transport. When the uid is not specified
-by the transport, but is associated with the address by a router, the option
-for calling &[initgroups()]& is taken from the router configuration.
-
-.cindex "&(pipe)& transport" "uid for"
-The &(pipe)& transport contains the special option &%pipe_as_creator%&. If this
-is set and &%user%& is not set, the uid of the process that called Exim to
-receive the message is used, and if &%group%& is not set, the corresponding
-original gid is also used.
-
-This is the detailed preference order for obtaining a gid; the first of the
-following that is set is used:
-
-.ilist
-A &%group%& setting of the transport;
-.next
-A &%group%& setting of the router;
-.next
-A gid associated with a user setting of the router, either as a result of
-&%check_local_user%& or an explicit non-numeric &%user%& setting;
-.next
-The group associated with a non-numeric &%user%& setting of the transport;
-.next
-In a &(pipe)& transport, the creator's gid if &%deliver_as_creator%& is set and
-the uid is the creator's uid;
-.next
-The Exim gid if the Exim uid is being used as a default.
-.endlist
-
-If, for example, the user is specified numerically on the router and there are
-no group settings, no gid is available. In this situation, an error occurs.
-This is different for the uid, for which there always is an ultimate default.
-The first of the following that is set is used:
-
-.ilist
-A &%user%& setting of the transport;
-.next
-In a &(pipe)& transport, the creator's uid if &%deliver_as_creator%& is set;
-.next
-A &%user%& setting of the router;
-.next
-A &%check_local_user%& setting of the router;
-.next
-The Exim uid.
-.endlist
-
-Of course, an error will still occur if the uid that is chosen is on the
-&%never_users%& list.
-
-
-
-
-
-.section "Current and home directories" "SECID132"
-.cindex "current directory for local transport"
-.cindex "home directory" "for local transport"
-.cindex "transport" "local; home directory for"
-.cindex "transport" "local; current directory for"
-Routers may set current and home directories for local transports by means of
-the &%transport_current_directory%& and &%transport_home_directory%& options.
-However, if the transport's &%current_directory%& or &%home_directory%& options
-are set, they override the router's values. In detail, the home directory
-for a local transport is taken from the first of these values that is set:
-
-.ilist
-The &%home_directory%& option on the transport;
-.next
-The &%transport_home_directory%& option on the router;
-.next
-The password data if &%check_local_user%& is set on the router;
-.next
-The &%router_home_directory%& option on the router.
-.endlist
-
-The current directory is taken from the first of these values that is set:
-
-.ilist
-The &%current_directory%& option on the transport;
-.next
-The &%transport_current_directory%& option on the router.
-.endlist
-
-
-If neither the router nor the transport sets a current directory, Exim uses the
-value of the home directory, if it is set. Otherwise it sets the current
-directory to &_/_& before running a local transport.
-
-
-
-.section "Expansion variables derived from the address" "SECID133"
-.vindex "&$domain$&"
-.vindex "&$local_part$&"
-.vindex "&$original_domain$&"
-Normally a local delivery is handling a single address, and in that case the
-variables such as &$domain$& and &$local_part$& are set during local
-deliveries. However, in some circumstances more than one address may be handled
-at once (for example, while writing batch SMTP for onward transmission by some
-other means). In this case, the variables associated with the local part are
-never set, &$domain$& is set only if all the addresses have the same domain,
-and &$original_domain$& is never set.
-.ecindex IIDenvlotra1
-.ecindex IIDenvlotra2
-.ecindex IIDenvlotra3
-
-
-
-
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "Generic options for transports" "CHAPtransportgeneric"
-.scindex IIDgenoptra1 "generic options" "transport"
-.scindex IIDgenoptra2 "options" "generic; for transports"
-.scindex IIDgenoptra3 "transport" "generic options for"
-The following generic options apply to all transports:
-
-
-.option body_only transports boolean false
-.cindex "transport" "body only"
-.cindex "message" "transporting body only"
-.cindex "body of message" "transporting"
-If this option is set, the message's headers are not transported. It is
-mutually exclusive with &%headers_only%&. If it is used with the &(appendfile)&
-or &(pipe)& transports, the settings of &%message_prefix%& and
-&%message_suffix%& should be checked, because this option does not
-automatically suppress them.
-
-
-.option current_directory transports string&!! unset
-.cindex "transport" "current directory for"
-This specifies the current directory that is to be set while running the
-transport, overriding any value that may have been set by the router.
-If the expansion fails for any reason, including forced failure, an error is
-logged, and delivery is deferred.
-
-
-.option disable_logging transports boolean false
-If this option is set true, nothing is logged for any
-deliveries by the transport or for any
-transport errors. You should not set this option unless you really, really know
-what you are doing.
-
-
-.option debug_print transports string&!! unset
-.cindex "testing" "variables in drivers"
-If this option is set and debugging is enabled (see the &%-d%& command line
-option), the string is expanded and included in the debugging output when the
-transport is run.
-If expansion of the string fails, the error message is written to the debugging
-output, and Exim carries on processing.
-This facility is provided to help with checking out the values of variables and
-so on when debugging driver configurations. For example, if a &%headers_add%&
-option is not working properly, &%debug_print%& could be used to output the
-variables it references. A newline is added to the text if it does not end with
-one.
-The variables &$transport_name$& and &$router_name$& contain the name of the
-transport and the router that called it.
-
-.option delivery_date_add transports boolean false
-.cindex "&'Delivery-date:'& header line"
-If this option is true, a &'Delivery-date:'& header is added to the message.
-This gives the actual time the delivery was made. As this is not a standard
-header, Exim has a configuration option (&%delivery_date_remove%&) which
-requests its removal from incoming messages, so that delivered messages can
-safely be resent to other recipients.
-
-
-.option driver transports string unset
-This specifies which of the available transport drivers is to be used.
-There is no default, and this option must be set for every transport.
-
-
-.option envelope_to_add transports boolean false
-.cindex "&'Envelope-to:'& header line"
-If this option is true, an &'Envelope-to:'& header is added to the message.
-This gives the original address(es) in the incoming envelope that caused this
-delivery to happen. More than one address may be present if the transport is
-configured to handle several addresses at once, or if more than one original
-address was redirected to the same final address. As this is not a standard
-header, Exim has a configuration option (&%envelope_to_remove%&) which requests
-its removal from incoming messages, so that delivered messages can safely be
-resent to other recipients.
-
-
-.option event_action transports string&!! unset
-.cindex events
-This option declares a string to be expanded for Exim's events mechanism.
-For details see chapter &<<CHAPevents>>&.
-
-
-.option group transports string&!! "Exim group"
-.cindex "transport" "group; specifying"
-This option specifies a gid for running the transport process, overriding any
-value that the router supplies, and also overriding any value associated with
-&%user%& (see below).
-
-
-.option headers_add transports list&!! unset
-.cindex "header lines" "adding in transport"
-.cindex "transport" "header lines; adding"
-This option specifies a list of text headers,
-newline-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
-which are (separately) expanded and added to the header
-portion of a message as it is transported, as described in section
-&<<SECTheadersaddrem>>&. Additional header lines can also be specified by
-routers. If the result of the expansion is an empty string, or if the expansion
-is forced to fail, no action is taken. Other expansion failures are treated as
-errors and cause the delivery to be deferred.
-
-Unlike most options, &%headers_add%& can be specified multiple times
-for a transport; all listed headers are added.
-
-
-.option headers_only transports boolean false
-.cindex "transport" "header lines only"
-.cindex "message" "transporting headers only"
-.cindex "header lines" "transporting"
-If this option is set, the message's body is not transported. It is mutually
-exclusive with &%body_only%&. If it is used with the &(appendfile)& or &(pipe)&
-transports, the settings of &%message_prefix%& and &%message_suffix%& should be
-checked, since this option does not automatically suppress them.
-
-
-.option headers_remove transports list&!! unset
-.cindex "header lines" "removing"
-.cindex "transport" "header lines; removing"
-This option specifies a list of text headers,
-colon-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
-to be removed from the message.
-However, the option has no effect when an address is just being verified.
-Each list item is separately expanded.
-If the result of the expansion is an empty string, or if the expansion
-is forced to fail, no action is taken. Other expansion failures are treated as
-errors and cause the delivery to be deferred.
-.new
-If an item ends in *, it will match any header with the given prefix.
-.wen
-
-Matching headers are omitted from the message as it is transported, as described
-in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
-routers.
-
-Unlike most options, &%headers_remove%& can be specified multiple times
-for a transport; all listed headers are removed.
-
-&*Warning*&: Because of the separate expansion of the list items,
-items that contain a list separator must have it doubled.
-To avoid this, change the list separator (&<<SECTlistsepchange>>&).
-
-
-
-.option headers_rewrite transports string unset
-.cindex "transport" "header lines; rewriting"
-.cindex "rewriting" "at transport time"
-This option allows addresses in header lines to be rewritten at transport time,
-that is, as the message is being copied to its destination. The contents of the
-option are a colon-separated list of rewriting rules. Each rule is in exactly
-the same form as one of the general rewriting rules that are applied when a
-message is received. These are described in chapter &<<CHAPrewrite>>&. For
-example,
-.code
-headers_rewrite = a@b c@d f : \
-                  x@y w@z
-.endd
-changes &'a@b'& into &'c@d'& in &'From:'& header lines, and &'x@y'& into
-&'w@z'& in all address-bearing header lines. The rules are applied to the
-header lines just before they are written out at transport time, so they affect
-only those copies of the message that pass through the transport. However, only
-the message's original header lines, and any that were added by a system
-filter, are rewritten. If a router or transport adds header lines, they are not
-affected by this option. These rewriting rules are &'not'& applied to the
-envelope. You can change the return path using &%return_path%&, but you cannot
-change envelope recipients at this time.
-
-
-.option home_directory transports string&!! unset
-.cindex "transport" "home directory for"
-.vindex "&$home$&"
-This option specifies a home directory setting for a local transport,
-overriding any value that may be set by the router. The home directory is
-placed in &$home$& while expanding the transport's private options. It is also
-used as the current directory if no current directory is set by the
-&%current_directory%& option on the transport or the
-&%transport_current_directory%& option on the router. If the expansion fails
-for any reason, including forced failure, an error is logged, and delivery is
-deferred.
-
-
-.option initgroups transports boolean false
-.cindex "additional groups"
-.cindex "groups" "additional"
-.cindex "transport" "group; additional"
-If this option is true and the uid for the delivery process is provided by the
-transport, the &[initgroups()]& function is called when running the transport
-to ensure that any additional groups associated with the uid are set up.
-
-
-.option max_parallel transports integer&!! unset
-.cindex limit "transport parallelism"
-.cindex transport "parallel processes"
-.cindex transport "concurrency limit"
-.cindex "delivery" "parallelism for transport"
-If this option is set and expands to an integer greater than zero
-it limits the number of concurrent runs of the transport.
-The control does not apply to shadow transports.
-
-.cindex "hints database" "transport concurrency control"
-Exim implements this control by means of a hints database in which a record is
-incremented whenever a transport process is being created. The record
-is decremented and possibly removed when the process terminates.
-Obviously there is scope for
-records to get left lying around if there is a system or program crash. To
-guard against this, Exim ignores any records that are more than six hours old.
-
-If you use this option, you should also arrange to delete the
-relevant hints database whenever your system reboots. The names of the files
-start with &_misc_& and they are kept in the &_spool/db_& directory. There
-may be one or two files, depending on the type of DBM in use. The same files
-are used for ETRN and smtp transport serialization.
-
-
-.option message_size_limit transports string&!! 0
-.cindex "limit" "message size per transport"
-.cindex "size" "of message, limit"
-.cindex "transport" "message size; limiting"
-This option controls the size of messages passed through the transport. It is
-expanded before use; the result of the expansion must be a sequence of decimal
-digits, optionally followed by K or M. If the expansion fails for any reason,
-including forced failure, or if the result is not of the required form,
-delivery is deferred. If the value is greater than zero and the size of a
-message exceeds this limit, the address is failed. If there is any chance that
-the resulting bounce message could be routed to the same transport, you should
-ensure that &%return_size_limit%& is less than the transport's
-&%message_size_limit%&, as otherwise the bounce message will fail to get
-delivered.
-
-
-
-.option rcpt_include_affixes transports boolean false
-.cindex "prefix" "for local part, including in envelope"
-.cindex "suffix for local part" "including in envelope"
-.cindex "local part" "prefix"
-.cindex "local part" "suffix"
-When this option is false (the default), and an address that has had any
-affixes (prefixes or suffixes) removed from the local part is delivered by any
-form of SMTP or LMTP, the affixes are not included. For example, if a router
-that contains
-.code
-local_part_prefix = *-
-.endd
-routes the address &'abc-xyz@some.domain'& to an SMTP transport, the envelope
-is delivered with
-.code
-RCPT TO:<xyz@some.domain>
-.endd
-This is also the case when an ACL-time callout is being used to verify a
-recipient address. However, if &%rcpt_include_affixes%& is set true, the
-whole local part is included in the RCPT command. This option applies to BSMTP
-deliveries by the &(appendfile)& and &(pipe)& transports as well as to the
-&(lmtp)& and &(smtp)& transports.
-
-
-.option retry_use_local_part transports boolean "see below"
-.cindex "hints database" "retry keys"
-When a delivery suffers a temporary failure, a retry record is created
-in Exim's hints database. For remote deliveries, the key for the retry record
-is based on the name and/or IP address of the failing remote host. For local
-deliveries, the key is normally the entire address, including both the local
-part and the domain. This is suitable for most common cases of local delivery
-temporary failure &-- for example, exceeding a mailbox quota should delay only
-deliveries to that mailbox, not to the whole domain.
-
-However, in some special cases you may want to treat a temporary local delivery
-as a failure associated with the domain, and not with a particular local part.
-(For example, if you are storing all mail for some domain in files.) You can do
-this by setting &%retry_use_local_part%& false.
-
-For all the local transports, its default value is true. For remote transports,
-the default value is false for tidiness, but changing the value has no effect
-on a remote transport in the current implementation.
-
-
-.option return_path transports string&!! unset
-.cindex "envelope sender"
-.cindex "envelope from"
-.cindex "transport" "return path; changing"
-.cindex "return path" "changing in transport"
-If this option is set, the string is expanded at transport time and replaces
-the existing return path (envelope sender) value in the copy of the message
-that is being delivered. An empty return path is permitted. This feature is
-designed for remote deliveries, where the value of this option is used in the
-SMTP MAIL command. If you set &%return_path%& for a local transport, the
-only effect is to change the address that is placed in the &'Return-path:'&
-header line, if one is added to the message (see the next option).
-
-&*Note:*& A changed return path is not logged unless you add
-&%return_path_on_delivery%& to the log selector.
-
-.vindex "&$return_path$&"
-The expansion can refer to the existing value via &$return_path$&. This is
-either the message's envelope sender, or an address set by the
-&%errors_to%& option on a router. If the expansion is forced to fail, no
-replacement occurs; if it fails for another reason, delivery is deferred. This
-option can be used to support VERP (Variable Envelope Return Paths) &-- see
-section &<<SECTverp>>&.
-
-&*Note*&: If a delivery error is detected locally, including the case when a
-remote server rejects a message at SMTP time, the bounce message is not sent to
-the value of this option. It is sent to the previously set errors address.
-This defaults to the incoming sender address, but can be changed by setting
-&%errors_to%& in a router.
-
-
-
-.option return_path_add transports boolean false
-.cindex "&'Return-path:'& header line"
-If this option is true, a &'Return-path:'& header is added to the message.
-Although the return path is normally available in the prefix line of BSD
-mailboxes, this is commonly not displayed by MUAs, and so the user does not
-have easy access to it.
-
-RFC 2821 states that the &'Return-path:'& header is added to a message &"when
-the delivery SMTP server makes the final delivery"&. This implies that this
-header should not be present in incoming messages. Exim has a configuration
-option, &%return_path_remove%&, which requests removal of this header from
-incoming messages, so that delivered messages can safely be resent to other
-recipients.
-
-
-.option shadow_condition transports string&!! unset
-See &%shadow_transport%& below.
-
-
-.option shadow_transport transports string unset
-.cindex "shadow transport"
-.cindex "transport" "shadow"
-A local transport may set the &%shadow_transport%& option to the name of
-another local transport. Shadow remote transports are not supported.
-
-Whenever a delivery to the main transport succeeds, and either
-&%shadow_condition%& is unset, or its expansion does not result in the empty
-string or one of the strings &"0"& or &"no"& or &"false"&, the message is also
-passed to the shadow transport, with the same delivery address or addresses. If
-expansion fails, no action is taken except that non-forced expansion failures
-cause a log line to be written.
-
-The result of the shadow transport is discarded and does not affect the
-subsequent processing of the message. Only a single level of shadowing is
-provided; the &%shadow_transport%& option is ignored on any transport when it
-is running as a shadow. Options concerned with output from pipes are also
-ignored. The log line for the successful delivery has an item added on the end,
-of the form
-.code
-ST=<shadow transport name>
-.endd
-If the shadow transport did not succeed, the error message is put in
-parentheses afterwards. Shadow transports can be used for a number of different
-purposes, including keeping more detailed log information than Exim normally
-provides, and implementing automatic acknowledgment policies based on message
-headers that some sites insist on.
-
-
-.option transport_filter transports string&!! unset
-.cindex "transport" "filter"
-.cindex "filter" "transport filter"
-This option sets up a filtering (in the Unix shell sense) process for messages
-at transport time. It should not be confused with mail filtering as set up by
-individual users or via a system filter.
-If unset, or expanding to an empty string, no filtering is done.
-
-When the message is about to be written out, the command specified by
-&%transport_filter%& is started up in a separate, parallel process, and
-the entire message, including the header lines, is passed to it on its standard
-input (this in fact is done from a third process, to avoid deadlock). The
-command must be specified as an absolute path.
-
-The lines of the message that are written to the transport filter are
-terminated by newline (&"\n"&). The message is passed to the filter before any
-SMTP-specific processing, such as turning &"\n"& into &"\r\n"& and escaping
-lines beginning with a dot, and also before any processing implied by the
-settings of &%check_string%& and &%escape_string%& in the &(appendfile)& or
-&(pipe)& transports.
-
-The standard error for the filter process is set to the same destination as its
-standard output; this is read and written to the message's ultimate
-destination. The process that writes the message to the filter, the
-filter itself, and the original process that reads the result and delivers it
-are all run in parallel, like a shell pipeline.
-
-The filter can perform any transformations it likes, but of course should take
-care not to break RFC 2822 syntax. Exim does not check the result, except to
-test for a final newline when SMTP is in use. All messages transmitted over
-SMTP must end with a newline, so Exim supplies one if it is missing.
-
-.cindex "content scanning" "per user"
-A transport filter can be used to provide content-scanning on a per-user basis
-at delivery time if the only required effect of the scan is to modify the
-message. For example, a content scan could insert a new header line containing
-a spam score. This could be interpreted by a filter in the user's MUA. It is
-not possible to discard a message at this stage.
-
-.cindex "SMTP" "SIZE"
-A problem might arise if the filter increases the size of a message that is
-being sent down an SMTP connection. If the receiving SMTP server has indicated
-support for the SIZE parameter, Exim will have sent the size of the message
-at the start of the SMTP session. If what is actually sent is substantially
-more, the server might reject the message. This can be worked round by setting
-the &%size_addition%& option on the &(smtp)& transport, either to allow for
-additions to the message, or to disable the use of SIZE altogether.
-
-.vindex "&$pipe_addresses$&"
-The value of the &%transport_filter%& option is the command string for starting
-the filter, which is run directly from Exim, not under a shell. The string is
-parsed by Exim in the same way as a command string for the &(pipe)& transport:
-Exim breaks it up into arguments and then expands each argument separately (see
-section &<<SECThowcommandrun>>&). Any kind of expansion failure causes delivery
-to be deferred. The special argument &$pipe_addresses$& is replaced by a number
-of arguments, one for each address that applies to this delivery. (This isn't
-an ideal name for this feature here, but as it was already implemented for the
-&(pipe)& transport, it seemed sensible not to change it.)
-
-.vindex "&$host$&"
-.vindex "&$host_address$&"
-The expansion variables &$host$& and &$host_address$& are available when the
-transport is a remote one. They contain the name and IP address of the host to
-which the message is being sent. For example:
-.code
-transport_filter = /some/directory/transport-filter.pl \
-  $host $host_address $sender_address $pipe_addresses
-.endd
-
-Two problems arise if you want to use more complicated expansion items to
-generate transport filter commands, both of which due to the fact that the
-command is split up &'before'& expansion.
-.ilist
-If an expansion item contains white space, you must quote it, so that it is all
-part of the same command item. If the entire option setting is one such
-expansion item, you have to take care what kind of quoting you use. For
-example:
-.code
-transport_filter = '/bin/cmd${if eq{$host}{a.b.c}{1}{2}}'
-.endd
-This runs the command &(/bin/cmd1)& if the host name is &'a.b.c'&, and
-&(/bin/cmd2)& otherwise. If double quotes had been used, they would have been
-stripped by Exim when it read the option's value. When the value is used, if
-the single quotes were missing, the line would be split into two items,
-&`/bin/cmd${if`& and &`eq{$host}{a.b.c}{1}{2}`&, and an error would occur when
-Exim tried to expand the first one.
-.next
-Except for the special case of &$pipe_addresses$& that is mentioned above, an
-expansion cannot generate multiple arguments, or a command name followed by
-arguments. Consider this example:
-.code
-transport_filter = ${lookup{$host}lsearch{/a/file}\
-                    {$value}{/bin/cat}}
-.endd
-The result of the lookup is interpreted as the name of the command, even
-if it contains white space. The simplest way round this is to use a shell:
-.code
-transport_filter = /bin/sh -c ${lookup{$host}lsearch{/a/file}\
-                               {$value}{/bin/cat}}
-.endd
-.endlist
-
-The filter process is run under the same uid and gid as the normal delivery.
-For remote deliveries this is the Exim uid/gid by default. The command should
-normally yield a zero return code. Transport filters are not supposed to fail.
-A non-zero code is taken to mean that the transport filter encountered some
-serious problem. Delivery of the message is deferred; the message remains on
-the queue and is tried again later. It is not possible to cause a message to be
-bounced from a transport filter.
-
-If a transport filter is set on an autoreply transport, the original message is
-passed through the filter as it is being copied into the newly generated
-message, which happens if the &%return_message%& option is set.
-
-
-.option transport_filter_timeout transports time 5m
-.cindex "transport" "filter, timeout"
-When Exim is reading the output of a transport filter, it applies a timeout
-that can be set by this option. Exceeding the timeout is normally treated as a
-temporary delivery failure. However, if a transport filter is used with a
-&(pipe)& transport, a timeout in the transport filter is treated in the same
-way as a timeout in the pipe command itself. By default, a timeout is a hard
-error, but if the &(pipe)& transport's &%timeout_defer%& option is set true, it
-becomes a temporary error.
-
-
-.option user transports string&!! "Exim user"
-.cindex "uid (user id)" "local delivery"
-.cindex "transport" "user, specifying"
-This option specifies the user under whose uid the delivery process is to be
-run, overriding any uid that may have been set by the router. If the user is
-given as a name, the uid is looked up from the password data, and the
-associated group is taken as the value of the gid to be used if the &%group%&
-option is not set.
-
-For deliveries that use local transports, a user and group are normally
-specified explicitly or implicitly (for example, as a result of
-&%check_local_user%&) by the router or transport.
-
-.cindex "hints database" "access by remote transport"
-For remote transports, you should leave this option unset unless you really are
-sure you know what you are doing. When a remote transport is running, it needs
-to be able to access Exim's hints databases, because each host may have its own
-retry data.
-.ecindex IIDgenoptra1
-.ecindex IIDgenoptra2
-.ecindex IIDgenoptra3
-
-
-
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "Address batching in local transports" "CHAPbatching" &&&
-         "Address batching"
-.cindex "transport" "local; address batching in"
-The only remote transport (&(smtp)&) is normally configured to handle more than
-one address at a time, so that when several addresses are routed to the same
-remote host, just one copy of the message is sent. Local transports, however,
-normally handle one address at a time. That is, a separate instance of the
-transport is run for each address that is routed to the transport. A separate
-copy of the message is delivered each time.
-
-.cindex "batched local delivery"
-.oindex "&%batch_max%&"
-.oindex "&%batch_id%&"
-In special cases, it may be desirable to handle several addresses at once in a
-local transport, for example:
-
-.ilist
-In an &(appendfile)& transport, when storing messages in files for later
-delivery by some other means, a single copy of the message with multiple
-recipients saves space.
-.next
-In an &(lmtp)& transport, when delivering over &"local SMTP"& to some process,
-a single copy saves time, and is the normal way LMTP is expected to work.
-.next
-In a &(pipe)& transport, when passing the message
-to a scanner program or
-to some other delivery mechanism such as UUCP, multiple recipients may be
-acceptable.
-.endlist
-
-These three local transports all have the same options for controlling multiple
-(&"batched"&) deliveries, namely &%batch_max%& and &%batch_id%&. To save
-repeating the information for each transport, these options are described here.
-
-The &%batch_max%& option specifies the maximum number of addresses that can be
-delivered together in a single run of the transport. Its default value is one
-(no batching). When more than one address is routed to a transport that has a
-&%batch_max%& value greater than one, the addresses are delivered in a batch
-(that is, in a single run of the transport with multiple recipients), subject
-to certain conditions:
-
-.ilist
-.vindex "&$local_part$&"
-If any of the transport's options contain a reference to &$local_part$&, no
-batching is possible.
-.next
-.vindex "&$domain$&"
-If any of the transport's options contain a reference to &$domain$&, only
-addresses with the same domain are batched.
-.next
-.cindex "customizing" "batching condition"
-If &%batch_id%& is set, it is expanded for each address, and only those
-addresses with the same expanded value are batched. This allows you to specify
-customized batching conditions. Failure of the expansion for any reason,
-including forced failure, disables batching, but it does not stop the delivery
-from taking place.
-.next
-Batched addresses must also have the same errors address (where to send
-delivery errors), the same header additions and removals, the same user and
-group for the transport, and if a host list is present, the first host must
-be the same.
-.endlist
-
-In the case of the &(appendfile)& and &(pipe)& transports, batching applies
-both when the file or pipe command is specified in the transport, and when it
-is specified by a &(redirect)& router, but all the batched addresses must of
-course be routed to the same file or pipe command. These two transports have an
-option called &%use_bsmtp%&, which causes them to deliver the message in
-&"batched SMTP"& format, with the envelope represented as SMTP commands. The
-&%check_string%& and &%escape_string%& options are forced to the values
-.code
-check_string = "."
-escape_string = ".."
-.endd
-when batched SMTP is in use. A full description of the batch SMTP mechanism is
-given in section &<<SECTbatchSMTP>>&. The &(lmtp)& transport does not have a
-&%use_bsmtp%& option, because it always delivers using the SMTP protocol.
-
-.cindex "&'Envelope-to:'& header line"
-If the generic &%envelope_to_add%& option is set for a batching transport, the
-&'Envelope-to:'& header that is added to the message contains all the addresses
-that are being processed together. If you are using a batching &(appendfile)&
-transport without &%use_bsmtp%&, the only way to preserve the recipient
-addresses is to set the &%envelope_to_add%& option.
-
-.cindex "&(pipe)& transport" "with multiple addresses"
-.vindex "&$pipe_addresses$&"
-If you are using a &(pipe)& transport without BSMTP, and setting the
-transport's &%command%& option, you can include &$pipe_addresses$& as part of
-the command. This is not a true variable; it is a bit of magic that causes each
-of the recipient addresses to be inserted into the command as a separate
-argument. This provides a way of accessing all the addresses that are being
-delivered in the batch. &*Note:*& This is not possible for pipe commands that
-are specified by a &(redirect)& router.
-
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "The appendfile transport" "CHAPappendfile"
-.scindex IIDapptra1 "&(appendfile)& transport"
-.scindex IIDapptra2 "transports" "&(appendfile)&"
-.cindex "directory creation"
-.cindex "creating directories"
-The &(appendfile)& transport delivers a message by appending it to an existing
-file, or by creating an entirely new file in a specified directory. Single
-files to which messages are appended can be in the traditional Unix mailbox
-format, or optionally in the MBX format supported by the Pine MUA and
-University of Washington IMAP daemon, &'inter alia'&. When each message is
-being delivered as a separate file, &"maildir"& format can optionally be used
-to give added protection against failures that happen part-way through the
-delivery. A third form of separate-file delivery known as &"mailstore"& is also
-supported. For all file formats, Exim attempts to create as many levels of
-directory as necessary, provided that &%create_directory%& is set.
-
-The code for the optional formats is not included in the Exim binary by
-default. It is necessary to set SUPPORT_MBX, SUPPORT_MAILDIR and/or
-SUPPORT_MAILSTORE in &_Local/Makefile_& to have the appropriate code
-included.
-
-.cindex "quota" "system"
-Exim recognizes system quota errors, and generates an appropriate message. Exim
-also supports its own quota control within the transport, for use when the
-system facility is unavailable or cannot be used for some reason.
-
-If there is an error while appending to a file (for example, quota exceeded or
-partition filled), Exim attempts to reset the file's length and last
-modification time back to what they were before. If there is an error while
-creating an entirely new file, the new file is removed.
-
-Before appending to a file, a number of security checks are made, and the
-file is locked. A detailed description is given below, after the list of
-private options.
-
-The &(appendfile)& transport is most commonly used for local deliveries to
-users' mailboxes. However, it can also be used as a pseudo-remote transport for
-putting messages into files for remote delivery by some means other than Exim.
-&"Batch SMTP"& format is often used in this case (see the &%use_bsmtp%&
-option).
-
-
-
-.section "The file and directory options" "SECTfildiropt"
-The &%file%& option specifies a single file, to which the message is appended;
-the &%directory%& option specifies a directory, in which a new file containing
-the message is created. Only one of these two options can be set, and for
-normal deliveries to mailboxes, one of them &'must'& be set.
-
-.vindex "&$address_file$&"
-.vindex "&$local_part$&"
-However, &(appendfile)& is also used for delivering messages to files or
-directories whose names (or parts of names) are obtained from alias,
-forwarding, or filtering operations (for example, a &%save%& command in a
-user's Exim filter). When such a transport is running, &$local_part$& contains
-the local part that was aliased or forwarded, and &$address_file$& contains the
-name (or partial name) of the file or directory generated by the redirection
-operation. There are two cases:
-
-.ilist
-If neither &%file%& nor &%directory%& is set, the redirection operation
-must specify an absolute path (one that begins with &`/`&). This is the most
-common case when users with local accounts use filtering to sort mail into
-different folders. See for example, the &(address_file)& transport in the
-default configuration. If the path ends with a slash, it is assumed to be the
-name of a directory. A delivery to a directory can also be forced by setting
-&%maildir_format%& or &%mailstore_format%&.
-.next
-If &%file%& or &%directory%& is set for a delivery from a redirection, it is
-used to determine the file or directory name for the delivery. Normally, the
-contents of &$address_file$& are used in some way in the string expansion.
-.endlist
-.new
-.cindex "tainted data" "in filenames"
-.cindex appendfile "tainted data"
-Tainted data may not be used for a file or directory name.
-This means that, for instance, &$local_part$& cannot be used directly
-as a component of a path.  It can however be used as the key for a lookup
-which returns a path (or component).
-.wen
-
-
-.cindex "Sieve filter" "configuring &(appendfile)&"
-.cindex "Sieve filter" "relative mailbox path handling"
-As an example of the second case, consider an environment where users do not
-have home directories. They may be permitted to use Exim filter commands of the
-form:
-.code
-save folder23
-.endd
-or Sieve filter commands of the form:
-.code
-require "fileinto";
-fileinto "folder23";
-.endd
-In this situation, the expansion of &%file%& or &%directory%& in the transport
-must transform the relative path into an appropriate absolute filename. In the
-case of Sieve filters, the name &'inbox'& must be handled. It is the name that
-is used as a result of a &"keep"& action in the filter. This example shows one
-way of handling this requirement:
-.code
-file = ${if eq{$address_file}{inbox} \
-            {/var/mail/$local_part} \
-            {${if eq{${substr_0_1:$address_file}}{/} \
-                  {$address_file} \
-                  {$home/mail/$address_file} \
-            }} \
-       }
-.endd
-With this setting of &%file%&, &'inbox'& refers to the standard mailbox
-location, absolute paths are used without change, and other folders are in the
-&_mail_& directory within the home directory.
-
-&*Note 1*&: While processing an Exim filter, a relative path such as
-&_folder23_& is turned into an absolute path if a home directory is known to
-the router. In particular, this is the case if &%check_local_user%& is set. If
-you want to prevent this happening at routing time, you can set
-&%router_home_directory%& empty. This forces the router to pass the relative
-path to the transport.
-
-&*Note 2*&: An absolute path in &$address_file$& is not treated specially;
-the &%file%& or &%directory%& option is still used if it is set.
-
-
-
-
-.section "Private options for appendfile" "SECID134"
-.cindex "options" "&(appendfile)& transport"
-
-
-
-.option allow_fifo appendfile boolean false
-.cindex "fifo (named pipe)"
-.cindex "named pipe (fifo)"
-.cindex "pipe" "named (fifo)"
-Setting this option permits delivery to named pipes (FIFOs) as well as to
-regular files. If no process is reading the named pipe at delivery time, the
-delivery is deferred.
-
-
-.option allow_symlink appendfile boolean false
-.cindex "symbolic link" "to mailbox"
-.cindex "mailbox" "symbolic link"
-By default, &(appendfile)& will not deliver if the path name for the file is
-that of a symbolic link. Setting this option relaxes that constraint, but there
-are security issues involved in the use of symbolic links. Be sure you know
-what you are doing if you set this. Details of exactly what this option affects
-are included in the discussion which follows this list of options.
-
-
-.option batch_id appendfile string&!! unset
-See the description of local delivery batching in chapter &<<CHAPbatching>>&.
-However, batching is automatically disabled for &(appendfile)& deliveries that
-happen as a result of forwarding or aliasing or other redirection directly to a
-file.
-
-
-.option batch_max appendfile integer 1
-See the description of local delivery batching in chapter &<<CHAPbatching>>&.
-
-
-.option check_group appendfile boolean false
-When this option is set, the group owner of the file defined by the &%file%&
-option is checked to see that it is the same as the group under which the
-delivery process is running. The default setting is false because the default
-file mode is 0600, which means that the group is irrelevant.
-
-
-.option check_owner appendfile boolean true
-When this option is set, the owner of the file defined by the &%file%& option
-is checked to ensure that it is the same as the user under which the delivery
-process is running.
-
-
-.option check_string appendfile string "see below"
-.cindex "&""From""& line"
-As &(appendfile)& writes the message, the start of each line is tested for
-matching &%check_string%&, and if it does, the initial matching characters are
-replaced by the contents of &%escape_string%&. The value of &%check_string%& is
-a literal string, not a regular expression, and the case of any letters it
-contains is significant.
-
-If &%use_bsmtp%& is set the values of &%check_string%& and &%escape_string%&
-are forced to &"."& and &".."& respectively, and any settings in the
-configuration are ignored. Otherwise, they default to &"From&~"& and
-&">From&~"& when the &%file%& option is set, and unset when any of the
-&%directory%&, &%maildir%&, or &%mailstore%& options are set.
-
-The default settings, along with &%message_prefix%& and &%message_suffix%&, are
-suitable for traditional &"BSD"& mailboxes, where a line beginning with
-&"From&~"& indicates the start of a new message. All four options need changing
-if another format is used. For example, to deliver to mailboxes in MMDF format:
-.cindex "MMDF format mailbox"
-.cindex "mailbox" "MMDF format"
-.code
-check_string = "\1\1\1\1\n"
-escape_string = "\1\1\1\1 \n"
-message_prefix = "\1\1\1\1\n"
-message_suffix = "\1\1\1\1\n"
-.endd
-.option create_directory appendfile boolean true
-.cindex "directory creation"
-When this option is true, Exim attempts to create any missing superior
-directories for the file that it is about to write. A created directory's mode
-is given by the &%directory_mode%& option.
-
-The group ownership of a newly created directory is highly dependent on the
-operating system (and possibly the file system) that is being used. For
-example, in Solaris, if the parent directory has the setgid bit set, its group
-is propagated to the child; if not, the currently set group is used. However,
-in FreeBSD, the parent's group is always used.
-
-
-
-.option create_file appendfile string anywhere
-This option constrains the location of files and directories that are created
-by this transport. It applies to files defined by the &%file%& option and
-directories defined by the &%directory%& option. In the case of maildir
-delivery, it applies to the top level directory, not the maildir directories
-beneath.
-
-The option must be set to one of the words &"anywhere"&, &"inhome"&, or
-&"belowhome"&. In the second and third cases, a home directory must have been
-set for the transport. This option is not useful when an explicit filename is
-given for normal mailbox deliveries. It is intended for the case when filenames
-are generated from users' &_.forward_& files. These are usually handled
-by an &(appendfile)& transport called &%address_file%&. See also
-&%file_must_exist%&.
-
-
-.option directory appendfile string&!! unset
-This option is mutually exclusive with the &%file%& option, but one of &%file%&
-or &%directory%& must be set, unless the delivery is the direct result of a
-redirection (see section &<<SECTfildiropt>>&).
-
-When &%directory%& is set, the string is expanded, and the message is delivered
-into a new file or files in or below the given directory, instead of being
-appended to a single mailbox file. A number of different formats are provided
-(see &%maildir_format%& and &%mailstore_format%&), and see section
-&<<SECTopdir>>& for further details of this form of delivery.
-
-
-.option directory_file appendfile string&!! "see below"
-.cindex "base62"
-.vindex "&$inode$&"
-When &%directory%& is set, but neither &%maildir_format%& nor
-&%mailstore_format%& is set, &(appendfile)& delivers each message into a file
-whose name is obtained by expanding this string. The default value is:
-.code
-q${base62:$tod_epoch}-$inode
-.endd
-This generates a unique name from the current time, in base 62 form, and the
-inode of the file. The variable &$inode$& is available only when expanding this
-option.
-
-
-.option directory_mode appendfile "octal integer" 0700
-If &(appendfile)& creates any directories as a result of the
-&%create_directory%& option, their mode is specified by this option.
-
-
-.option escape_string appendfile string "see description"
-See &%check_string%& above.
-
-
-.option file appendfile string&!! unset
-This option is mutually exclusive with the &%directory%& option, but one of
-&%file%& or &%directory%& must be set, unless the delivery is the direct result
-of a redirection (see section &<<SECTfildiropt>>&). The &%file%& option
-specifies a single file, to which the message is appended. One or more of
-&%use_fcntl_lock%&, &%use_flock_lock%&, or &%use_lockfile%& must be set with
-&%file%&.
-
-.cindex "NFS" "lock file"
-.cindex "locking files"
-.cindex "lock files"
-If you are using more than one host to deliver over NFS into the same
-mailboxes, you should always use lock files.
-
-The string value is expanded for each delivery, and must yield an absolute
-path. The most common settings of this option are variations on one of these
-examples:
-.code
-file = /var/spool/mail/$local_part
-file = /home/$local_part/inbox
-file = $home/inbox
-.endd
-.cindex "&""sticky""& bit"
-In the first example, all deliveries are done into the same directory. If Exim
-is configured to use lock files (see &%use_lockfile%& below) it must be able to
-create a file in the directory, so the &"sticky"& bit must be turned on for
-deliveries to be possible, or alternatively the &%group%& option can be used to
-run the delivery under a group id which has write access to the directory.
-
-
-
-.option file_format appendfile string unset
-.cindex "file" "mailbox; checking existing format"
-This option requests the transport to check the format of an existing file
-before adding to it. The check consists of matching a specific string at the
-start of the file. The value of the option consists of an even number of
-colon-separated strings. The first of each pair is the test string, and the
-second is the name of a transport. If the transport associated with a matched
-string is not the current transport, control is passed over to the other
-transport. For example, suppose the standard &(local_delivery)& transport has
-this added to it:
-.code
-file_format = "From       : local_delivery :\
-               \1\1\1\1\n : local_mmdf_delivery"
-.endd
-Mailboxes that begin with &"From"& are still handled by this transport, but if
-a mailbox begins with four binary ones followed by a newline, control is passed
-to a transport called &%local_mmdf_delivery%&, which presumably is configured
-to do the delivery in MMDF format. If a mailbox does not exist or is empty, it
-is assumed to match the current transport. If the start of a mailbox doesn't
-match any string, or if the transport named for a given string is not defined,
-delivery is deferred.
-
-
-.option file_must_exist appendfile boolean false
-If this option is true, the file specified by the &%file%& option must exist.
-A temporary error occurs if it does not, causing delivery to be deferred.
-If this option is false, the file is created if it does not exist.
-
-
-.option lock_fcntl_timeout appendfile time 0s
-.cindex "timeout" "mailbox locking"
-.cindex "mailbox" "locking, blocking and non-blocking"
-.cindex "locking files"
-By default, the &(appendfile)& transport uses non-blocking calls to &[fcntl()]&
-when locking an open mailbox file. If the call fails, the delivery process
-sleeps for &%lock_interval%& and tries again, up to &%lock_retries%& times.
-Non-blocking calls are used so that the file is not kept open during the wait
-for the lock; the reason for this is to make it as safe as possible for
-deliveries over NFS in the case when processes might be accessing an NFS
-mailbox without using a lock file. This should not be done, but
-misunderstandings and hence misconfigurations are not unknown.
-
-On a busy system, however, the performance of a non-blocking lock approach is
-not as good as using a blocking lock with a timeout. In this case, the waiting
-is done inside the system call, and Exim's delivery process acquires the lock
-and can proceed as soon as the previous lock holder releases it.
-
-If &%lock_fcntl_timeout%& is set to a non-zero time, blocking locks, with that
-timeout, are used. There may still be some retrying: the maximum number of
-retries is
-.code
-(lock_retries * lock_interval) / lock_fcntl_timeout
-.endd
-rounded up to the next whole number. In other words, the total time during
-which &(appendfile)& is trying to get a lock is roughly the same, unless
-&%lock_fcntl_timeout%& is set very large.
-
-You should consider setting this option if you are getting a lot of delayed
-local deliveries because of errors of the form
-.code
-failed to lock mailbox /some/file (fcntl)
-.endd
-
-.option lock_flock_timeout appendfile time 0s
-This timeout applies to file locking when using &[flock()]& (see
-&%use_flock%&); the timeout operates in a similar manner to
-&%lock_fcntl_timeout%&.
-
-
-.option lock_interval appendfile time 3s
-This specifies the time to wait between attempts to lock the file. See below
-for details of locking.
-
-
-.option lock_retries appendfile integer 10
-This specifies the maximum number of attempts to lock the file. A value of zero
-is treated as 1. See below for details of locking.
-
-
-.option lockfile_mode appendfile "octal integer" 0600
-This specifies the mode of the created lock file, when a lock file is being
-used (see &%use_lockfile%& and &%use_mbx_lock%&).
-
-
-.option lockfile_timeout appendfile time 30m
-.cindex "timeout" "mailbox locking"
-When a lock file is being used (see &%use_lockfile%&), if a lock file already
-exists and is older than this value, it is assumed to have been left behind by
-accident, and Exim attempts to remove it.
-
-
-.option mailbox_filecount appendfile string&!! unset
-.cindex "mailbox" "specifying size of"
-.cindex "size" "of mailbox"
-If this option is set, it is expanded, and the result is taken as the current
-number of files in the mailbox. It must be a decimal number, optionally
-followed by K or M. This provides a way of obtaining this information from an
-external source that maintains the data.
-
-
-.option mailbox_size appendfile string&!! unset
-.cindex "mailbox" "specifying size of"
-.cindex "size" "of mailbox"
-If this option is set, it is expanded, and the result is taken as the current
-size the mailbox. It must be a decimal number, optionally followed by K or M.
-This provides a way of obtaining this information from an external source that
-maintains the data. This is likely to be helpful for maildir deliveries where
-it is computationally expensive to compute the size of a mailbox.
-
-
-
-.option maildir_format appendfile boolean false
-.cindex "maildir format" "specifying"
-If this option is set with the &%directory%& option, the delivery is into a new
-file, in the &"maildir"& format that is used by other mail software. When the
-transport is activated directly from a &(redirect)& router (for example, the
-&(address_file)& transport in the default configuration), setting
-&%maildir_format%& causes the path received from the router to be treated as a
-directory, whether or not it ends with &`/`&. This option is available only if
-SUPPORT_MAILDIR is present in &_Local/Makefile_&. See section
-&<<SECTmaildirdelivery>>& below for further details.
-
-
-.option maildir_quota_directory_regex appendfile string "See below"
-.cindex "maildir format" "quota; directories included in"
-.cindex "quota" "maildir; directories included in"
-This option is relevant only when &%maildir_use_size_file%& is set. It defines
-a regular expression for specifying directories, relative to the quota
-directory (see &%quota_directory%&), that should be included in the quota
-calculation. The default value is:
-.code
-maildir_quota_directory_regex = ^(?:cur|new|\..*)$
-.endd
-This includes the &_cur_& and &_new_& directories, and any maildir++ folders
-(directories whose names begin with a dot). If you want to exclude the
-&_Trash_&
-folder from the count (as some sites do), you need to change this setting to
-.code
-maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$
-.endd
-This uses a negative lookahead in the regular expression to exclude the
-directory whose name is &_.Trash_&. When a directory is excluded from quota
-calculations, quota processing is bypassed for any messages that are delivered
-directly into that directory.
-
-
-.option maildir_retries appendfile integer 10
-This option specifies the number of times to retry when writing a file in
-&"maildir"& format. See section &<<SECTmaildirdelivery>>& below.
-
-
-.option maildir_tag appendfile string&!! unset
-This option applies only to deliveries in maildir format, and is described in
-section &<<SECTmaildirdelivery>>& below.
-
-
-.option maildir_use_size_file appendfile&!! boolean false
-.cindex "maildir format" "&_maildirsize_& file"
-The result of string expansion for this option must be a valid boolean value.
-If it is true, it enables support for &_maildirsize_& files. Exim
-creates a &_maildirsize_& file in a maildir if one does not exist, taking the
-quota from the &%quota%& option of the transport. If &%quota%& is unset, the
-value is zero. See &%maildir_quota_directory_regex%& above and section
-&<<SECTmaildirdelivery>>& below for further details.
-
-.option maildirfolder_create_regex appendfile string unset
-.cindex "maildir format" "&_maildirfolder_& file"
-.cindex "&_maildirfolder_&, creating"
-The value of this option is a regular expression. If it is unset, it has no
-effect. Otherwise, before a maildir delivery takes place, the pattern is
-matched against the name of the maildir directory, that is, the directory
-containing the &_new_& and &_tmp_& subdirectories that will be used for the
-delivery. If there is a match, Exim checks for the existence of a file called
-&_maildirfolder_& in the directory, and creates it if it does not exist.
-See section &<<SECTmaildirdelivery>>& for more details.
-
-
-.option mailstore_format appendfile boolean false
-.cindex "mailstore format" "specifying"
-If this option is set with the &%directory%& option, the delivery is into two
-new files in  &"mailstore"& format. The option is available only if
-SUPPORT_MAILSTORE is present in &_Local/Makefile_&. See section &<<SECTopdir>>&
-below for further details.
-
-
-.option mailstore_prefix appendfile string&!! unset
-This option applies only to deliveries in mailstore format, and is described in
-section &<<SECTopdir>>& below.
-
-
-.option mailstore_suffix appendfile string&!! unset
-This option applies only to deliveries in mailstore format, and is described in
-section &<<SECTopdir>>& below.
-
-
-.option mbx_format appendfile boolean false
-.cindex "locking files"
-.cindex "file" "locking"
-.cindex "file" "MBX format"
-.cindex "MBX format, specifying"
-This option is available only if Exim has been compiled with SUPPORT_MBX
-set in &_Local/Makefile_&. If &%mbx_format%& is set with the &%file%& option,
-the message is appended to the mailbox file in MBX format instead of
-traditional Unix format. This format is supported by Pine4 and its associated
-IMAP and POP daemons, by means of the &'c-client'& library that they all use.
-
-&*Note*&: The &%message_prefix%& and &%message_suffix%& options are not
-automatically changed by the use of &%mbx_format%&. They should normally be set
-empty when using MBX format, so this option almost always appears in this
-combination:
-.code
-mbx_format = true
-message_prefix =
-message_suffix =
-.endd
-If none of the locking options are mentioned in the configuration,
-&%use_mbx_lock%& is assumed and the other locking options default to false. It
-is possible to specify the other kinds of locking with &%mbx_format%&, but
-&%use_fcntl_lock%& and &%use_mbx_lock%& are mutually exclusive. MBX locking
-interworks with &'c-client'&, providing for shared access to the mailbox. It
-should not be used if any program that does not use this form of locking is
-going to access the mailbox, nor should it be used if the mailbox file is NFS
-mounted, because it works only when the mailbox is accessed from a single host.
-
-If you set &%use_fcntl_lock%& with an MBX-format mailbox, you cannot use
-the standard version of &'c-client'&, because as long as it has a mailbox open
-(this means for the whole of a Pine or IMAP session), Exim will not be able to
-append messages to it.
-
-
-.option message_prefix appendfile string&!! "see below"
-.cindex "&""From""& line"
-The string specified here is expanded and output at the start of every message.
-The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
-in which case it is:
-.code
-message_prefix = "From ${if def:return_path{$return_path}\
-  {MAILER-DAEMON}} $tod_bsdinbox\n"
-.endd
-&*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
-&`\n`& to &`\r\n`& in &%message_prefix%&.
-
-.option message_suffix appendfile string&!! "see below"
-The string specified here is expanded and output at the end of every message.
-The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
-in which case it is a single newline character. The suffix can be suppressed by
-setting
-.code
-message_suffix =
-.endd
-&*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
-&`\n`& to &`\r\n`& in &%message_suffix%&.
-
-.option mode appendfile "octal integer" 0600
-If the output file is created, it is given this mode. If it already exists and
-has wider permissions, they are reduced to this mode. If it has narrower
-permissions, an error occurs unless &%mode_fail_narrower%& is false. However,
-if the delivery is the result of a &%save%& command in a filter file specifying
-a particular mode, the mode of the output file is always forced to take that
-value, and this option is ignored.
-
-
-.option mode_fail_narrower appendfile boolean true
-This option applies in the case when an existing mailbox file has a narrower
-mode than that specified by the &%mode%& option. If &%mode_fail_narrower%& is
-true, the delivery is deferred (&"mailbox has the wrong mode"&); otherwise Exim
-continues with the delivery attempt, using the existing mode of the file.
-
-
-.option notify_comsat appendfile boolean false
-If this option is true, the &'comsat'& daemon is notified after every
-successful delivery to a user mailbox. This is the daemon that notifies logged
-on users about incoming mail.
-
-
-.option quota appendfile string&!! unset
-.cindex "quota" "imposed by Exim"
-This option imposes a limit on the size of the file to which Exim is appending,
-or to the total space used in the directory tree when the &%directory%& option
-is set. In the latter case, computation of the space used is expensive, because
-all the files in the directory (and any sub-directories) have to be
-individually inspected and their sizes summed. (See &%quota_size_regex%& and
-&%maildir_use_size_file%& for ways to avoid this in environments where users
-have no shell access to their mailboxes).
-
-As there is no interlock against two simultaneous deliveries into a
-multi-file mailbox, it is possible for the quota to be overrun in this case.
-For single-file mailboxes, of course, an interlock is a necessity.
-
-A file's size is taken as its &'used'& value. Because of blocking effects, this
-may be a lot less than the actual amount of disk space allocated to the file.
-If the sizes of a number of files are being added up, the rounding effect can
-become quite noticeable, especially on systems that have large block sizes.
-Nevertheless, it seems best to stick to the &'used'& figure, because this is
-the obvious value which users understand most easily.
-
-The value of the option is expanded, and must then be a numerical value
-(decimal point allowed), optionally followed by one of the letters K, M, or G,
-for kilobytes, megabytes, or gigabytes, optionally followed by a slash
-and further option modifiers. If Exim is running on a system with
-large file support (Linux and FreeBSD have this), mailboxes larger than 2G can
-be handled.
-
-The option modifier &%no_check%& can be used to force delivery even if the over
-quota condition is met. The quota gets updated as usual.
-
-&*Note*&: A value of zero is interpreted as &"no quota"&.
-
-The expansion happens while Exim is running as root, before it changes uid for
-the delivery. This means that files that are inaccessible to the end user can
-be used to hold quota values that are looked up in the expansion. When delivery
-fails because this quota is exceeded, the handling of the error is as for
-system quota failures.
-
-By default, Exim's quota checking mimics system quotas, and restricts the
-mailbox to the specified maximum size, though the value is not accurate to the
-last byte, owing to separator lines and additional headers that may get added
-during message delivery. When a mailbox is nearly full, large messages may get
-refused even though small ones are accepted, because the size of the current
-message is added to the quota when the check is made. This behaviour can be
-changed by setting &%quota_is_inclusive%& false. When this is done, the check
-for exceeding the quota does not include the current message. Thus, deliveries
-continue until the quota has been exceeded; thereafter, no further messages are
-delivered. See also &%quota_warn_threshold%&.
-
-
-.option quota_directory appendfile string&!! unset
-This option defines the directory to check for quota purposes when delivering
-into individual files. The default is the delivery directory, or, if a file
-called &_maildirfolder_& exists in a maildir directory, the parent of the
-delivery directory.
-
-
-.option quota_filecount appendfile string&!! 0
-This option applies when the &%directory%& option is set. It limits the total
-number of files in the directory (compare the inode limit in system quotas). It
-can only be used if &%quota%& is also set. The value is expanded; an expansion
-failure causes delivery to be deferred. A value of zero is interpreted as
-&"no quota"&.
-
-The option modifier &%no_check%& can be used to force delivery even if the over
-quota condition is met. The quota gets updated as usual.
-
-.option quota_is_inclusive appendfile boolean true
-See &%quota%& above.
-
-
-.option quota_size_regex appendfile string unset
-This option applies when one of the delivery modes that writes a separate file
-for each message is being used. When Exim wants to find the size of one of
-these files in order to test the quota, it first checks &%quota_size_regex%&.
-If this is set to a regular expression that matches the filename, and it
-captures one string, that string is interpreted as a representation of the
-file's size. The value of &%quota_size_regex%& is not expanded.
-
-This feature is useful only when users have no shell access to their mailboxes
-&-- otherwise they could defeat the quota simply by renaming the files. This
-facility can be used with maildir deliveries, by setting &%maildir_tag%& to add
-the file length to the filename. For example:
-.code
-maildir_tag = ,S=$message_size
-quota_size_regex = ,S=(\d+)
-.endd
-An alternative to &$message_size$& is &$message_linecount$&, which contains the
-number of lines in the message.
-
-The regular expression should not assume that the length is at the end of the
-filename (even though &%maildir_tag%& puts it there) because maildir MUAs
-sometimes add other information onto the ends of message filenames.
-
-Section &<<SECID136>>& contains further information.
-
-This option should not be used when other message-handling software
-may duplicate messages by making hardlinks to the files.  When that is done Exim
-will count the message size once for each filename, in contrast with the actual
-disk usage.  When the option is not set, calculating total usage requires
-a system-call per file to get the size; the number of links is then available also
-as is used to adjust the effective size.
-
-
-.option quota_warn_message appendfile string&!! "see below"
-See below for the use of this option. If it is not set when
-&%quota_warn_threshold%& is set, it defaults to
-.code
-quota_warn_message = "\
-  To: $local_part@$domain\n\
-  Subject: Your mailbox\n\n\
-  This message is automatically created \
-  by mail delivery software.\n\n\
-  The size of your mailbox has exceeded \
-  a warning threshold that is\n\
-  set by the system administrator.\n"
-.endd
-
-
-.option quota_warn_threshold appendfile string&!! 0
-.cindex "quota" "warning threshold"
-.cindex "mailbox" "size warning"
-.cindex "size" "of mailbox"
-This option is expanded in the same way as &%quota%& (see above). If the
-resulting value is greater than zero, and delivery of the message causes the
-size of the file or total space in the directory tree to cross the given
-threshold, a warning message is sent. If &%quota%& is also set, the threshold
-may be specified as a percentage of it by following the value with a percent
-sign. For example:
-.code
-quota = 10M
-quota_warn_threshold = 75%
-.endd
-If &%quota%& is not set, a setting of &%quota_warn_threshold%& that ends with a
-percent sign is ignored.
-
-The warning message itself is specified by the &%quota_warn_message%& option,
-and it must start with a &'To:'& header line containing the recipient(s) of the
-warning message. These do not necessarily have to include the recipient(s) of
-the original message. A &'Subject:'& line should also normally be supplied. You
-can include any other header lines that you want. If you do not include a
-&'From:'& line, the default is:
-.code
-From: Mail Delivery System <mailer-daemon@$qualify_domain_sender>
-.endd
-.oindex &%errors_reply_to%&
-If you supply a &'Reply-To:'& line, it overrides the global &%errors_reply_to%&
-option.
-
-The &%quota%& option does not have to be set in order to use this option; they
-are independent of one another except when the threshold is specified as a
-percentage.
-
-
-.option use_bsmtp appendfile boolean false
-.cindex "envelope from"
-.cindex "envelope sender"
-If this option is set true, &(appendfile)& writes messages in &"batch SMTP"&
-format, with the envelope sender and recipient(s) included as SMTP commands. If
-you want to include a leading HELO command with such messages, you can do
-so by setting the &%message_prefix%& option. See section &<<SECTbatchSMTP>>&
-for details of batch SMTP.
-
-
-.option use_crlf appendfile boolean false
-.cindex "carriage return"
-.cindex "linefeed"
-This option causes lines to be terminated with the two-character CRLF sequence
-(carriage return, linefeed) instead of just a linefeed character. In the case
-of batched SMTP, the byte sequence written to the file is then an exact image
-of what would be sent down a real SMTP connection.
-
-&*Note:*& The contents of the &%message_prefix%& and &%message_suffix%& options
-(which are used to supply the traditional &"From&~"& and blank line separators
-in Berkeley-style mailboxes) are written verbatim, so must contain their own
-carriage return characters if these are needed. In cases where these options
-have non-empty defaults, the values end with a single linefeed, so they must be
-changed to end with &`\r\n`& if &%use_crlf%& is set.
-
-
-.option use_fcntl_lock appendfile boolean "see below"
-This option controls the use of the &[fcntl()]& function to lock a file for
-exclusive use when a message is being appended. It is set by default unless
-&%use_flock_lock%& is set. Otherwise, it should be turned off only if you know
-that all your MUAs use lock file locking. When both &%use_fcntl_lock%& and
-&%use_flock_lock%& are unset, &%use_lockfile%& must be set.
-
-
-.option use_flock_lock appendfile boolean false
-This option is provided to support the use of &[flock()]& for file locking, for
-the few situations where it is needed. Most modern operating systems support
-&[fcntl()]& and &[lockf()]& locking, and these two functions interwork with
-each other. Exim uses &[fcntl()]& locking by default.
-
-This option is required only if you are using an operating system where
-&[flock()]& is used by programs that access mailboxes (typically MUAs), and
-where &[flock()]& does not correctly interwork with &[fcntl()]&. You can use
-both &[fcntl()]& and &[flock()]& locking simultaneously if you want.
-
-.cindex "Solaris" "&[flock()]& support"
-Not all operating systems provide &[flock()]&. Some versions of Solaris do not
-have it (and some, I think, provide a not quite right version built on top of
-&[lockf()]&). If the OS does not have &[flock()]&, Exim will be built without
-the ability to use it, and any attempt to do so will cause a configuration
-error.
-
-&*Warning*&: &[flock()]& locks do not work on NFS files (unless &[flock()]&
-is just being mapped onto &[fcntl()]& by the OS).
-
-
-.option use_lockfile appendfile boolean "see below"
-If this option is turned off, Exim does not attempt to create a lock file when
-appending to a mailbox file. In this situation, the only locking is by
-&[fcntl()]&. You should only turn &%use_lockfile%& off if you are absolutely
-sure that every MUA that is ever going to look at your users' mailboxes uses
-&[fcntl()]& rather than a lock file, and even then only when you are not
-delivering over NFS from more than one host.
-
-.cindex "NFS" "lock file"
-In order to append to an NFS file safely from more than one host, it is
-necessary to take out a lock &'before'& opening the file, and the lock file
-achieves this. Otherwise, even with &[fcntl()]& locking, there is a risk of
-file corruption.
-
-The &%use_lockfile%& option is set by default unless &%use_mbx_lock%& is set.
-It is not possible to turn both &%use_lockfile%& and &%use_fcntl_lock%& off,
-except when &%mbx_format%& is set.
-
-
-.option use_mbx_lock appendfile boolean "see below"
-This option is available only if Exim has been compiled with SUPPORT_MBX
-set in &_Local/Makefile_&. Setting the option specifies that special MBX
-locking rules be used. It is set by default if &%mbx_format%& is set and none
-of the locking options are mentioned in the configuration. The locking rules
-are the same as are used by the &'c-client'& library that underlies Pine and
-the IMAP4 and POP daemons that come with it (see the discussion below). The
-rules allow for shared access to the mailbox. However, this kind of locking
-does not work when the mailbox is NFS mounted.
-
-You can set &%use_mbx_lock%& with either (or both) of &%use_fcntl_lock%& and
-&%use_flock_lock%& to control what kind of locking is used in implementing the
-MBX locking rules. The default is to use &[fcntl()]& if &%use_mbx_lock%& is set
-without &%use_fcntl_lock%& or &%use_flock_lock%&.
-
-
-
-
-.section "Operational details for appending" "SECTopappend"
-.cindex "appending to a file"
-.cindex "file" "appending"
-Before appending to a file, the following preparations are made:
-
-.ilist
-If the name of the file is &_/dev/null_&, no action is taken, and a success
-return is given.
-
-.next
-.cindex "directory creation"
-If any directories on the file's path are missing, Exim creates them if the
-&%create_directory%& option is set. A created directory's mode is given by the
-&%directory_mode%& option.
-
-.next
-If &%file_format%& is set, the format of an existing file is checked. If this
-indicates that a different transport should be used, control is passed to that
-transport.
-
-.next
-.cindex "file" "locking"
-.cindex "locking files"
-.cindex "NFS" "lock file"
-If &%use_lockfile%& is set, a lock file is built in a way that will work
-reliably over NFS, as follows:
-
-.olist
-Create a &"hitching post"& file whose name is that of the lock file with the
-current time, primary host name, and process id added, by opening for writing
-as a new file. If this fails with an access error, delivery is deferred.
-.next
-Close the hitching post file, and hard link it to the lock filename.
-.next
-If the call to &[link()]& succeeds, creation of the lock file has succeeded.
-Unlink the hitching post name.
-.next
-Otherwise, use &[stat()]& to get information about the hitching post file, and
-then unlink hitching post name. If the number of links is exactly two, creation
-of the lock file succeeded but something (for example, an NFS server crash and
-restart) caused this fact not to be communicated to the &[link()]& call.
-.next
-If creation of the lock file failed, wait for &%lock_interval%& and try again,
-up to &%lock_retries%& times. However, since any program that writes to a
-mailbox should complete its task very quickly, it is reasonable to time out old
-lock files that are normally the result of user agent and system crashes. If an
-existing lock file is older than &%lockfile_timeout%& Exim attempts to unlink
-it before trying again.
-.endlist olist
-
-.next
-A call is made to &[lstat()]& to discover whether the main file exists, and if
-so, what its characteristics are. If &[lstat()]& fails for any reason other
-than non-existence, delivery is deferred.
-
-.next
-.cindex "symbolic link" "to mailbox"
-.cindex "mailbox" "symbolic link"
-If the file does exist and is a symbolic link, delivery is deferred, unless the
-&%allow_symlink%& option is set, in which case the ownership of the link is
-checked, and then &[stat()]& is called to find out about the real file, which
-is then subjected to the checks below. The check on the top-level link
-ownership prevents one user creating a link for another's mailbox in a sticky
-directory, though allowing symbolic links in this case is definitely not a good
-idea. If there is a chain of symbolic links, the intermediate ones are not
-checked.
-
-.next
-If the file already exists but is not a regular file, or if the file's owner
-and group (if the group is being checked &-- see &%check_group%& above) are
-different from the user and group under which the delivery is running,
-delivery is deferred.
-
-.next
-If the file's permissions are more generous than specified, they are reduced.
-If they are insufficient, delivery is deferred, unless &%mode_fail_narrower%&
-is set false, in which case the delivery is tried using the existing
-permissions.
-
-.next
-The file's inode number is saved, and the file is then opened for appending.
-If this fails because the file has vanished, &(appendfile)& behaves as if it
-hadn't existed (see below). For any other failures, delivery is deferred.
-
-.next
-If the file is opened successfully, check that the inode number hasn't
-changed, that it is still a regular file, and that the owner and permissions
-have not changed. If anything is wrong, defer delivery and freeze the message.
-
-.next
-If the file did not exist originally, defer delivery if the &%file_must_exist%&
-option is set. Otherwise, check that the file is being created in a permitted
-directory if the &%create_file%& option is set (deferring on failure), and then
-open for writing as a new file, with the O_EXCL and O_CREAT options,
-except when dealing with a symbolic link (the &%allow_symlink%& option must be
-set). In this case, which can happen if the link points to a non-existent file,
-the file is opened for writing using O_CREAT but not O_EXCL, because
-that prevents link following.
-
-.next
-.cindex "loop" "while file testing"
-If opening fails because the file exists, obey the tests given above for
-existing files. However, to avoid looping in a situation where the file is
-being continuously created and destroyed, the exists/not-exists loop is broken
-after 10 repetitions, and the message is then frozen.
-
-.next
-If opening fails with any other error, defer delivery.
-
-.next
-.cindex "file" "locking"
-.cindex "locking files"
-Once the file is open, unless both &%use_fcntl_lock%& and &%use_flock_lock%&
-are false, it is locked using &[fcntl()]& or &[flock()]& or both. If
-&%use_mbx_lock%& is false, an exclusive lock is requested in each case.
-However, if &%use_mbx_lock%& is true, Exim takes out a shared lock on the open
-file, and an exclusive lock on the file whose name is
-.code
-/tmp/.<device-number>.<inode-number>
-.endd
-using the device and inode numbers of the open mailbox file, in accordance with
-the MBX locking rules. This file is created with a mode that is specified by
-the &%lockfile_mode%& option.
-
-If Exim fails to lock the file, there are two possible courses of action,
-depending on the value of the locking timeout. This is obtained from
-&%lock_fcntl_timeout%& or &%lock_flock_timeout%&, as appropriate.
-
-If the timeout value is zero, the file is closed, Exim waits for
-&%lock_interval%&, and then goes back and re-opens the file as above and tries
-to lock it again. This happens up to &%lock_retries%& times, after which the
-delivery is deferred.
-
-If the timeout has a value greater than zero, blocking calls to &[fcntl()]& or
-&[flock()]& are used (with the given timeout), so there has already been some
-waiting involved by the time locking fails. Nevertheless, Exim does not give up
-immediately. It retries up to
-.code
-(lock_retries * lock_interval) / <timeout>
-.endd
-times (rounded up).
-.endlist
-
-At the end of delivery, Exim closes the file (which releases the &[fcntl()]&
-and/or &[flock()]& locks) and then deletes the lock file if one was created.
-
-
-.section "Operational details for delivery to a new file" "SECTopdir"
-.cindex "delivery" "to single file"
-.cindex "&""From""& line"
-When the &%directory%& option is set instead of &%file%&, each message is
-delivered into a newly-created file or set of files. When &(appendfile)& is
-activated directly from a &(redirect)& router, neither &%file%& nor
-&%directory%& is normally set, because the path for delivery is supplied by the
-router. (See for example, the &(address_file)& transport in the default
-configuration.) In this case, delivery is to a new file if either the path name
-ends in &`/`&, or the &%maildir_format%& or &%mailstore_format%& option is set.
-
-No locking is required while writing the message to a new file, so the various
-locking options of the transport are ignored. The &"From"& line that by default
-separates messages in a single file is not normally needed, nor is the escaping
-of message lines that start with &"From"&, and there is no need to ensure a
-newline at the end of each message. Consequently, the default values for
-&%check_string%&, &%message_prefix%&, and &%message_suffix%& are all unset when
-any of &%directory%&, &%maildir_format%&, or &%mailstore_format%& is set.
-
-If Exim is required to check a &%quota%& setting, it adds up the sizes of all
-the files in the delivery directory by default. However, you can specify a
-different directory by setting &%quota_directory%&. Also, for maildir
-deliveries (see below) the &_maildirfolder_& convention is honoured.
-
-
-.cindex "maildir format"
-.cindex "mailstore format"
-There are three different ways in which delivery to individual files can be
-done, controlled by the settings of the &%maildir_format%& and
-&%mailstore_format%& options. Note that code to support maildir or mailstore
-formats is not included in the binary unless SUPPORT_MAILDIR or
-SUPPORT_MAILSTORE, respectively, is set in &_Local/Makefile_&.
-
-.cindex "directory creation"
-In all three cases an attempt is made to create the directory and any necessary
-sub-directories if they do not exist, provided that the &%create_directory%&
-option is set (the default). The location of a created directory can be
-constrained by setting &%create_file%&. A created directory's mode is given by
-the &%directory_mode%& option. If creation fails, or if the
-&%create_directory%& option is not set when creation is required, delivery is
-deferred.
-
-
-
-.section "Maildir delivery" "SECTmaildirdelivery"
-.cindex "maildir format" "description of"
-If the &%maildir_format%& option is true, Exim delivers each message by writing
-it to a file whose name is &_tmp/<stime>.H<mtime>P<pid>.<host>_& in the
-directory that is defined by the &%directory%& option (the &"delivery
-directory"&). If the delivery is successful, the file is renamed into the
-&_new_& subdirectory.
-
-In the filename, <&'stime'&> is the current time of day in seconds, and
-<&'mtime'&> is the microsecond fraction of the time. After a maildir delivery,
-Exim checks that the time-of-day clock has moved on by at least one microsecond
-before terminating the delivery process. This guarantees uniqueness for the
-filename. However, as a precaution, Exim calls &[stat()]& for the file before
-opening it. If any response other than ENOENT (does not exist) is given,
-Exim waits 2 seconds and tries again, up to &%maildir_retries%& times.
-
-Before Exim carries out a maildir delivery, it ensures that subdirectories
-called &_new_&, &_cur_&, and &_tmp_& exist in the delivery directory. If they
-do not exist, Exim tries to create them and any superior directories in their
-path, subject to the &%create_directory%& and &%create_file%& options. If the
-&%maildirfolder_create_regex%& option is set, and the regular expression it
-contains matches the delivery directory, Exim also ensures that a file called
-&_maildirfolder_& exists in the delivery directory. If a missing directory or
-&_maildirfolder_& file cannot be created, delivery is deferred.
-
-These features make it possible to use Exim to create all the necessary files
-and directories in a maildir mailbox, including subdirectories for maildir++
-folders. Consider this example:
-.code
-maildir_format = true
-directory = /var/mail/$local_part\
-           ${if eq{$local_part_suffix}{}{}\
-           {/.${substr_1:$local_part_suffix}}}
-maildirfolder_create_regex = /\.[^/]+$
-.endd
-If &$local_part_suffix$& is empty (there was no suffix for the local part),
-delivery is into a toplevel maildir with a name like &_/var/mail/pimbo_& (for
-the user called &'pimbo'&). The pattern in &%maildirfolder_create_regex%& does
-not match this name, so Exim will not look for or create the file
-&_/var/mail/pimbo/maildirfolder_&, though it will create
-&_/var/mail/pimbo/{cur,new,tmp}_& if necessary.
-
-However, if &$local_part_suffix$& contains &`-eximusers`& (for example),
-delivery is into the maildir++ folder &_/var/mail/pimbo/.eximusers_&, which
-does match &%maildirfolder_create_regex%&. In this case, Exim will create
-&_/var/mail/pimbo/.eximusers/maildirfolder_& as well as the three maildir
-directories &_/var/mail/pimbo/.eximusers/{cur,new,tmp}_&.
-
-&*Warning:*& Take care when setting &%maildirfolder_create_regex%& that it does
-not inadvertently match the toplevel maildir directory, because a
-&_maildirfolder_& file at top level would completely break quota calculations.
-
-.cindex "quota" "in maildir delivery"
-.cindex "maildir++"
-If Exim is required to check a &%quota%& setting before a maildir delivery, and
-&%quota_directory%& is not set, it looks for a file called &_maildirfolder_& in
-the maildir directory (alongside &_new_&, &_cur_&, &_tmp_&). If this exists,
-Exim assumes the directory is a maildir++ folder directory, which is one level
-down from the user's top level mailbox directory. This causes it to start at
-the parent directory instead of the current directory when calculating the
-amount of space used.
-
-One problem with delivering into a multi-file mailbox is that it is
-computationally expensive to compute the size of the mailbox for quota
-checking. Various approaches have been taken to reduce the amount of work
-needed. The next two sections describe two of them. A third alternative is to
-use some external process for maintaining the size data, and use the expansion
-of the &%mailbox_size%& option as a way of importing it into Exim.
-
-
-
-
-.section "Using tags to record message sizes" "SECID135"
-If &%maildir_tag%& is set, the string is expanded for each delivery.
-When the maildir file is renamed into the &_new_& sub-directory, the
-tag is added to its name. However, if adding the tag takes the length of the
-name to the point where the test &[stat()]& call fails with ENAMETOOLONG,
-the tag is dropped and the maildir file is created with no tag.
-
-
-.vindex "&$message_size$&"
-Tags can be used to encode the size of files in their names; see
-&%quota_size_regex%& above for an example. The expansion of &%maildir_tag%&
-happens after the message has been written. The value of the &$message_size$&
-variable is set to the number of bytes actually written. If the expansion is
-forced to fail, the tag is ignored, but a non-forced failure causes delivery to
-be deferred. The expanded tag may contain any printing characters except &"/"&.
-Non-printing characters in the string are ignored; if the resulting string is
-empty, it is ignored. If it starts with an alphanumeric character, a leading
-colon is inserted; this default has not proven to be the path that popular
-maildir implementations have chosen (but changing it in Exim would break
-backwards compatibility).
-
-For one common implementation, you might set:
-.code
-maildir_tag = ,S=${message_size}
-.endd
-but you should check the documentation of the other software to be sure.
-
-It is advisable to also set &%quota_size_regex%& when setting &%maildir_tag%&
-as this allows Exim to extract the size from your tag, instead of having to
-&[stat()]& each message file.
-
-
-.section "Using a maildirsize file" "SECID136"
-.cindex "quota" "in maildir delivery"
-.cindex "maildir format" "&_maildirsize_& file"
-If &%maildir_use_size_file%& is true, Exim implements the maildir++ rules for
-storing quota and message size information in a file called &_maildirsize_&
-within the toplevel maildir directory. If this file does not exist, Exim
-creates it, setting the quota from the &%quota%& option of the transport. If
-the maildir directory itself does not exist, it is created before any attempt
-to write a &_maildirsize_& file.
-
-The &_maildirsize_& file is used to hold information about the sizes of
-messages in the maildir, thus speeding up quota calculations. The quota value
-in the file is just a cache; if the quota is changed in the transport, the new
-value overrides the cached value when the next message is delivered. The cache
-is maintained for the benefit of other programs that access the maildir and
-need to know the quota.
-
-If the &%quota%& option in the transport is unset or zero, the &_maildirsize_&
-file is maintained (with a zero quota setting), but no quota is imposed.
-
-A regular expression is available for controlling which directories in the
-maildir participate in quota calculations when a &_maildirsizefile_& is in use.
-See the description of the &%maildir_quota_directory_regex%& option above for
-details.
-
-
-.section "Mailstore delivery" "SECID137"
-.cindex "mailstore format" "description of"
-If the &%mailstore_format%& option is true, each message is written as two
-files in the given directory. A unique base name is constructed from the
-message id and the current delivery process, and the files that are written use
-this base name plus the suffixes &_.env_& and &_.msg_&. The &_.env_& file
-contains the message's envelope, and the &_.msg_& file contains the message
-itself. The base name is placed in the variable &$mailstore_basename$&.
-
-During delivery, the envelope is first written to a file with the suffix
-&_.tmp_&. The &_.msg_& file is then written, and when it is complete, the
-&_.tmp_& file is renamed as the &_.env_& file. Programs that access messages in
-mailstore format should wait for the presence of both a &_.msg_& and a &_.env_&
-file before accessing either of them. An alternative approach is to wait for
-the absence of a &_.tmp_& file.
-
-The envelope file starts with any text defined by the &%mailstore_prefix%&
-option, expanded and terminated by a newline if there isn't one. Then follows
-the sender address on one line, then all the recipient addresses, one per line.
-There can be more than one recipient only if the &%batch_max%& option is set
-greater than one. Finally, &%mailstore_suffix%& is expanded and the result
-appended to the file, followed by a newline if it does not end with one.
-
-If expansion of &%mailstore_prefix%& or &%mailstore_suffix%& ends with a forced
-failure, it is ignored. Other expansion errors are treated as serious
-configuration errors, and delivery is deferred. The variable
-&$mailstore_basename$& is available for use during these expansions.
-
-
-.section "Non-special new file delivery" "SECID138"
-If neither &%maildir_format%& nor &%mailstore_format%& is set, a single new
-file is created directly in the named directory. For example, when delivering
-messages into files in batched SMTP format for later delivery to some host (see
-section &<<SECTbatchSMTP>>&), a setting such as
-.code
-directory = /var/bsmtp/$host
-.endd
-might be used. A message is written to a file with a temporary name, which is
-then renamed when the delivery is complete. The final name is obtained by
-expanding the contents of the &%directory_file%& option.
-.ecindex IIDapptra1
-.ecindex IIDapptra2
-
-
-
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "The autoreply transport" "CHID8"
-.scindex IIDauttra1 "transports" "&(autoreply)&"
-.scindex IIDauttra2 "&(autoreply)& transport"
-The &(autoreply)& transport is not a true transport in that it does not cause
-the message to be transmitted. Instead, it generates a new mail message as an
-automatic reply to the incoming message. &'References:'& and
-&'Auto-Submitted:'& header lines are included. These are constructed according
-to the rules in RFCs 2822 and 3834, respectively.
-
-If the router that passes the message to this transport does not have the
-&%unseen%& option set, the original message (for the current recipient) is not
-delivered anywhere. However, when the &%unseen%& option is set on the router
-that passes the message to this transport, routing of the address continues, so
-another router can set up a normal message delivery.
-
-
-The &(autoreply)& transport is usually run as the result of mail filtering, a
-&"vacation"& message being the standard example. However, it can also be run
-directly from a router like any other transport. To reduce the possibility of
-message cascades, messages created by the &(autoreply)& transport always have
-empty envelope sender addresses, like bounce messages.
-
-The parameters of the message to be sent can be specified in the configuration
-by options described below. However, these are used only when the address
-passed to the transport does not contain its own reply information. When the
-transport is run as a consequence of a
-&%mail%&
-or &%vacation%& command in a filter file, the parameters of the message are
-supplied by the filter, and passed with the address. The transport's options
-that define the message are then ignored (so they are not usually set in this
-case). The message is specified entirely by the filter or by the transport; it
-is never built from a mixture of options. However, the &%file_optional%&,
-&%mode%&, and &%return_message%& options apply in all cases.
-
-&(Autoreply)& is implemented as a local transport. When used as a result of a
-command in a user's filter file, &(autoreply)& normally runs under the uid and
-gid of the user, and with appropriate current and home directories (see chapter
-&<<CHAPenvironment>>&).
-
-There is a subtle difference between routing a message to a &(pipe)& transport
-that generates some text to be returned to the sender, and routing it to an
-&(autoreply)& transport. This difference is noticeable only if more than one
-address from the same message is so handled. In the case of a pipe, the
-separate outputs from the different addresses are gathered up and returned to
-the sender in a single message, whereas if &(autoreply)& is used, a separate
-message is generated for each address that is passed to it.
-
-Non-printing characters are not permitted in the header lines generated for the
-message that &(autoreply)& creates, with the exception of newlines that are
-immediately followed by white space. If any non-printing characters are found,
-the transport defers.
-Whether characters with the top bit set count as printing characters or not is
-controlled by the &%print_topbitchars%& global option.
-
-If any of the generic options for manipulating headers (for example,
-&%headers_add%&) are set on an &(autoreply)& transport, they apply to the copy
-of the original message that is included in the generated message when
-&%return_message%& is set. They do not apply to the generated message itself.
-
-.vindex "&$sender_address$&"
-If the &(autoreply)& transport receives return code 2 from Exim when it submits
-the message, indicating that there were no recipients, it does not treat this
-as an error. This means that autoreplies sent to &$sender_address$& when this
-is empty (because the incoming message is a bounce message) do not cause
-problems. They are just discarded.
-
-
-
-.section "Private options for autoreply" "SECID139"
-.cindex "options" "&(autoreply)& transport"
-
-.option bcc autoreply string&!! unset
-This specifies the addresses that are to receive &"blind carbon copies"& of the
-message when the message is specified by the transport.
-
-
-.option cc autoreply string&!! unset
-This specifies recipients of the message and the contents of the &'Cc:'& header
-when the message is specified by the transport.
-
-
-.option file autoreply string&!! unset
-The contents of the file are sent as the body of the message when the message
-is specified by the transport. If both &%file%& and &%text%& are set, the text
-string comes first.
-
-
-.option file_expand autoreply boolean false
-If this is set, the contents of the file named by the &%file%& option are
-subjected to string expansion as they are added to the message.
-
-
-.option file_optional autoreply boolean false
-If this option is true, no error is generated if the file named by the &%file%&
-option or passed with the address does not exist or cannot be read.
-
-
-.option from autoreply string&!! unset
-This specifies the contents of the &'From:'& header when the message is
-specified by the transport.
-
-
-.option headers autoreply string&!! unset
-This specifies additional RFC 2822 headers that are to be added to the message
-when the message is specified by the transport. Several can be given by using
-&"\n"& to separate them. There is no check on the format.
-
-
-.option log autoreply string&!! unset
-This option names a file in which a record of every message sent is logged when
-the message is specified by the transport.
-
-
-.option mode autoreply "octal integer" 0600
-If either the log file or the &"once"& file has to be created, this mode is
-used.
-
-
-.option never_mail autoreply "address list&!!" unset
-If any run of the transport creates a message with a recipient that matches any
-item in the list, that recipient is quietly discarded. If all recipients are
-discarded, no message is created. This applies both when the recipients are
-generated by a filter and when they are specified in the transport.
-
-
-
-.option once autoreply string&!! unset
-This option names a file or DBM database in which a record of each &'To:'&
-recipient is kept when the message is specified by the transport. &*Note*&:
-This does not apply to &'Cc:'& or &'Bcc:'& recipients.
-
-If &%once%& is unset, or is set to an empty string, the message is always sent.
-By default, if &%once%& is set to a non-empty filename, the message
-is not sent if a potential recipient is already listed in the database.
-However, if the &%once_repeat%& option specifies a time greater than zero, the
-message is sent if that much time has elapsed since a message was last sent to
-this recipient. A setting of zero time for &%once_repeat%& (the default)
-prevents a message from being sent a second time &-- in this case, zero means
-infinity.
-
-If &%once_file_size%& is zero, a DBM database is used to remember recipients,
-and it is allowed to grow as large as necessary. If &%once_file_size%& is set
-greater than zero, it changes the way Exim implements the &%once%& option.
-Instead of using a DBM file to record every recipient it sends to, it uses a
-regular file, whose size will never get larger than the given value.
-
-In the file, Exim keeps a linear list of recipient addresses and the times at
-which they were sent messages. If the file is full when a new address needs to
-be added, the oldest address is dropped. If &%once_repeat%& is not set, this
-means that a given recipient may receive multiple messages, but at
-unpredictable intervals that depend on the rate of turnover of addresses in the
-file. If &%once_repeat%& is set, it specifies a maximum time between repeats.
-
-
-.option once_file_size autoreply integer 0
-See &%once%& above.
-
-
-.option once_repeat autoreply time&!! 0s
-See &%once%& above.
-After expansion, the value of this option must be a valid time value.
-
-
-.option reply_to autoreply string&!! unset
-This specifies the contents of the &'Reply-To:'& header when the message is
-specified by the transport.
-
-
-.option return_message autoreply boolean false
-If this is set, a copy of the original message is returned with the new
-message, subject to the maximum size set in the &%return_size_limit%& global
-configuration option.
-
-
-.option subject autoreply string&!! unset
-This specifies the contents of the &'Subject:'& header when the message is
-specified by the transport. It is tempting to quote the original subject in
-automatic responses. For example:
-.code
-subject = Re: $h_subject:
-.endd
-There is a danger in doing this, however. It may allow a third party to
-subscribe your users to an opt-in mailing list, provided that the list accepts
-bounce messages as subscription confirmations. Well-managed lists require a
-non-bounce message to confirm a subscription, so the danger is relatively
-small.
-
-
-
-.option text autoreply string&!! unset
-This specifies a single string to be used as the body of the message when the
-message is specified by the transport. If both &%text%& and &%file%& are set,
-the text comes first.
-
-
-.option to autoreply string&!! unset
-This specifies recipients of the message and the contents of the &'To:'& header
-when the message is specified by the transport.
-.ecindex IIDauttra1
-.ecindex IIDauttra2
-
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "The lmtp transport" "CHAPLMTP"
-.cindex "transports" "&(lmtp)&"
-.cindex "&(lmtp)& transport"
-.cindex "LMTP" "over a pipe"
-.cindex "LMTP" "over a socket"
-The &(lmtp)& transport runs the LMTP protocol (RFC 2033) over a pipe to a
-specified command
-or by interacting with a Unix domain socket.
-This transport is something of a cross between the &(pipe)& and &(smtp)&
-transports. Exim also has support for using LMTP over TCP/IP; this is
-implemented as an option for the &(smtp)& transport. Because LMTP is expected
-to be of minority interest, the default build-time configure in &_src/EDITME_&
-has it commented out. You need to ensure that
-.code
-TRANSPORT_LMTP=yes
-.endd
-.cindex "options" "&(lmtp)& transport"
-is present in your &_Local/Makefile_& in order to have the &(lmtp)& transport
-included in the Exim binary. The private options of the &(lmtp)& transport are
-as follows:
-
-.option batch_id lmtp string&!! unset
-See the description of local delivery batching in chapter &<<CHAPbatching>>&.
-
-
-.option batch_max lmtp integer 1
-This limits the number of addresses that can be handled in a single delivery.
-Most LMTP servers can handle several addresses at once, so it is normally a
-good idea to increase this value. See the description of local delivery
-batching in chapter &<<CHAPbatching>>&.
-
-
-.option command lmtp string&!! unset
-This option must be set if &%socket%& is not set. The string is a command which
-is run in a separate process. It is split up into a command name and list of
-arguments, each of which is separately expanded (so expansion cannot change the
-number of arguments). The command is run directly, not via a shell. The message
-is passed to the new process using the standard input and output to operate the
-LMTP protocol.
-
-.option ignore_quota lmtp boolean false
-.cindex "LMTP" "ignoring quota errors"
-If this option is set true, the string &`IGNOREQUOTA`& is added to RCPT
-commands, provided that the LMTP server has advertised support for IGNOREQUOTA
-in its response to the LHLO command.
-
-.option socket lmtp string&!! unset
-This option must be set if &%command%& is not set. The result of expansion must
-be the name of a Unix domain socket. The transport connects to the socket and
-delivers the message to it using the LMTP protocol.
-
-
-.option timeout lmtp time 5m
-The transport is aborted if the created process or Unix domain socket does not
-respond to LMTP commands or message input within this timeout. Delivery
-is deferred, and will be tried again later. Here is an example of a typical
-LMTP transport:
-.code
-lmtp:
-  driver = lmtp
-  command = /some/local/lmtp/delivery/program
-  batch_max = 20
-  user = exim
-.endd
-This delivers up to 20 addresses at a time, in a mixture of domains if
-necessary, running as the user &'exim'&.
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "The pipe transport" "CHAPpipetransport"
-.scindex IIDpiptra1 "transports" "&(pipe)&"
-.scindex IIDpiptra2 "&(pipe)& transport"
-The &(pipe)& transport is used to deliver messages via a pipe to a command
-running in another process. One example is the use of &(pipe)& as a
-pseudo-remote transport for passing messages to some other delivery mechanism
-(such as UUCP). Another is the use by individual users to automatically process
-their incoming messages. The &(pipe)& transport can be used in one of the
-following ways:
-
-.ilist
-.vindex "&$local_part$&"
-A router routes one address to a transport in the normal way, and the
-transport is configured as a &(pipe)& transport. In this case, &$local_part$&
-contains the local part of the address (as usual), and the command that is run
-is specified by the &%command%& option on the transport.
-.next
-.vindex "&$pipe_addresses$&"
-If the &%batch_max%& option is set greater than 1 (the default is 1), the
-transport can handle more than one address in a single run. In this case, when
-more than one address is routed to the transport, &$local_part$& is not set
-(because it is not unique). However, the pseudo-variable &$pipe_addresses$&
-(described in section &<<SECThowcommandrun>>& below) contains all the addresses
-that are routed to the transport.
-.next
-.vindex "&$address_pipe$&"
-A router redirects an address directly to a pipe command (for example, from an
-alias or forward file). In this case, &$address_pipe$& contains the text of the
-pipe command, and the &%command%& option on the transport is ignored unless
-&%force_command%& is set. If only one address is being transported
-(&%batch_max%& is not greater than one, or only one address was redirected to
-this pipe command), &$local_part$& contains the local part that was redirected.
-.endlist
-
-
-The &(pipe)& transport is a non-interactive delivery method. Exim can also
-deliver messages over pipes using the LMTP interactive protocol. This is
-implemented by the &(lmtp)& transport.
-
-In the case when &(pipe)& is run as a consequence of an entry in a local user's
-&_.forward_& file, the command runs under the uid and gid of that user. In
-other cases, the uid and gid have to be specified explicitly, either on the
-transport or on the router that handles the address. Current and &"home"&
-directories are also controllable. See chapter &<<CHAPenvironment>>& for
-details of the local delivery environment and chapter &<<CHAPbatching>>&
-for a discussion of local delivery batching.
-
-.new
-.cindex "tainted data" "in pipe command"
-.cindex pipe "tainted data"
-Tainted data may not be used for the command name.
-.wen
-
-
-.section "Concurrent delivery" "SECID140"
-If two messages arrive at almost the same time, and both are routed to a pipe
-delivery, the two pipe transports may be run concurrently. You must ensure that
-any pipe commands you set up are robust against this happening. If the commands
-write to a file, the &%exim_lock%& utility might be of use.
-Alternatively the &%max_parallel%& option could be used with a value
-of "1" to enforce serialization.
-
-
-
-
-.section "Returned status and data" "SECID141"
-.cindex "&(pipe)& transport" "returned data"
-If the command exits with a non-zero return code, the delivery is deemed to
-have failed, unless either the &%ignore_status%& option is set (in which case
-the return code is treated as zero), or the return code is one of those listed
-in the &%temp_errors%& option, which are interpreted as meaning &"try again
-later"&. In this case, delivery is deferred. Details of a permanent failure are
-logged, but are not included in the bounce message, which merely contains
-&"local delivery failed"&.
-
-If the command exits on a signal and the &%freeze_signal%& option is set then
-the message will be frozen in the queue. If that option is not set, a bounce
-will be sent as normal.
-
-If the return code is greater than 128 and the command being run is a shell
-script, it normally means that the script was terminated by a signal whose
-value is the return code minus 128. The &%freeze_signal%& option does not
-apply in this case.
-
-If Exim is unable to run the command (that is, if &[execve()]& fails), the
-return code is set to 127. This is the value that a shell returns if it is
-asked to run a non-existent command. The wording for the log line suggests that
-a non-existent command may be the problem.
-
-The &%return_output%& option can affect the result of a pipe delivery. If it is
-set and the command produces any output on its standard output or standard
-error streams, the command is considered to have failed, even if it gave a zero
-return code or if &%ignore_status%& is set. The output from the command is
-included as part of the bounce message. The &%return_fail_output%& option is
-similar, except that output is returned only when the command exits with a
-failure return code, that is, a value other than zero or a code that matches
-&%temp_errors%&.
-
-
-
-.section "How the command is run" "SECThowcommandrun"
-.cindex "&(pipe)& transport" "path for command"
-The command line is (by default) broken down into a command name and arguments
-by the &(pipe)& transport itself. The &%allow_commands%& and
-&%restrict_to_path%& options can be used to restrict the commands that may be
-run.
-
-.cindex "quoting" "in pipe command"
-Unquoted arguments are delimited by white space. If an argument appears in
-double quotes, backslash is interpreted as an escape character in the usual
-way. If an argument appears in single quotes, no escaping is done.
-
-String expansion is applied to the command line except when it comes from a
-traditional &_.forward_& file (commands from a filter file are expanded). The
-expansion is applied to each argument in turn rather than to the whole line.
-For this reason, any string expansion item that contains white space must be
-quoted so as to be contained within a single argument. A setting such as
-.code
-command = /some/path ${if eq{$local_part}{postmaster}{xx}{yy}}
-.endd
-will not work, because the expansion item gets split between several
-arguments. You have to write
-.code
-command = /some/path "${if eq{$local_part}{postmaster}{xx}{yy}}"
-.endd
-to ensure that it is all in one argument. The expansion is done in this way,
-argument by argument, so that the number of arguments cannot be changed as a
-result of expansion, and quotes or backslashes in inserted variables do not
-interact with external quoting. However, this leads to problems if you want to
-generate multiple arguments (or the command name plus arguments) from a single
-expansion. In this situation, the simplest solution is to use a shell. For
-example:
-.code
-command = /bin/sh -c ${lookup{$local_part}lsearch{/some/file}}
-.endd
-
-.cindex "transport" "filter"
-.cindex "filter" "transport filter"
-.vindex "&$pipe_addresses$&"
-Special handling takes place when an argument consists of precisely the text
-&`$pipe_addresses`& (no quotes).
-This is not a general expansion variable; the only
-place this string is recognized is when it appears as an argument for a pipe or
-transport filter command. It causes each address that is being handled to be
-inserted in the argument list at that point &'as a separate argument'&. This
-avoids any problems with spaces or shell metacharacters, and is of use when a
-&(pipe)& transport is handling groups of addresses in a batch.
-
-If &%force_command%& is enabled on the transport, special handling takes place
-for an argument that consists of precisely the text &`$address_pipe`&.  It
-is handled similarly to &$pipe_addresses$& above.  It is expanded and each
-argument is inserted in the argument list at that point
-&'as a separate argument'&.  The &`$address_pipe`& item does not need to be
-the only item in the argument; in fact, if it were then &%force_command%&
-should behave as a no-op.  Rather, it should be used to adjust the command
-run while preserving the argument vector separation.
-
-After splitting up into arguments and expansion, the resulting command is run
-in a subprocess directly from the transport, &'not'& under a shell. The
-message that is being delivered is supplied on the standard input, and the
-standard output and standard error are both connected to a single pipe that is
-read by Exim. The &%max_output%& option controls how much output the command
-may produce, and the &%return_output%& and &%return_fail_output%& options
-control what is done with it.
-
-Not running the command under a shell (by default) lessens the security risks
-in cases when a command from a user's filter file is built out of data that was
-taken from an incoming message. If a shell is required, it can of course be
-explicitly specified as the command to be run. However, there are circumstances
-where existing commands (for example, in &_.forward_& files) expect to be run
-under a shell and cannot easily be modified. To allow for these cases, there is
-an option called &%use_shell%&, which changes the way the &(pipe)& transport
-works. Instead of breaking up the command line as just described, it expands it
-as a single string and passes the result to &_/bin/sh_&. The
-&%restrict_to_path%& option and the &$pipe_addresses$& facility cannot be used
-with &%use_shell%&, and the whole mechanism is inherently less secure.
-
-
-
-.section "Environment variables" "SECTpipeenv"
-.cindex "&(pipe)& transport" "environment for command"
-.cindex "environment" "&(pipe)& transport"
-The environment variables listed below are set up when the command is invoked.
-This list is a compromise for maximum compatibility with other MTAs. Note that
-the &%environment%& option can be used to add additional variables to this
-environment. The environment for the &(pipe)& transport is not subject
-to the &%add_environment%& and &%keep_environment%& main config options.
-.display
-&`DOMAIN            `&   the domain of the address
-&`HOME              `&   the home directory, if set
-&`HOST              `&   the host name when called from a router (see below)
-&`LOCAL_PART        `&   see below
-&`LOCAL_PART_PREFIX `&   see below
-&`LOCAL_PART_SUFFIX `&   see below
-&`LOGNAME           `&   see below
-&`MESSAGE_ID        `&   Exim's local ID for the message
-&`PATH              `&   as specified by the &%path%& option below
-&`QUALIFY_DOMAIN    `&   the sender qualification domain
-&`RECIPIENT         `&   the complete recipient address
-&`SENDER            `&   the sender of the message (empty if a bounce)
-&`SHELL             `&   &`/bin/sh`&
-&`TZ                `&   the value of the &%timezone%& option, if set
-&`USER              `&   see below
-.endd
-When a &(pipe)& transport is called directly from (for example) an &(accept)&
-router, LOCAL_PART is set to the local part of the address. When it is
-called as a result of a forward or alias expansion, LOCAL_PART is set to
-the local part of the address that was expanded. In both cases, any affixes are
-removed from the local part, and made available in LOCAL_PART_PREFIX and
-LOCAL_PART_SUFFIX, respectively. LOGNAME and USER are set to the
-same value as LOCAL_PART for compatibility with other MTAs.
-
-.cindex "HOST"
-HOST is set only when a &(pipe)& transport is called from a router that
-associates hosts with an address, typically when using &(pipe)& as a
-pseudo-remote transport. HOST is set to the first host name specified by
-the router.
-
-.cindex "HOME"
-If the transport's generic &%home_directory%& option is set, its value is used
-for the HOME environment variable. Otherwise, a home directory may be set
-by the router's &%transport_home_directory%& option, which defaults to the
-user's home directory if &%check_local_user%& is set.
-
-
-.section "Private options for pipe" "SECID142"
-.cindex "options" "&(pipe)& transport"
-
-
-
-.option allow_commands pipe "string list&!!" unset
-.cindex "&(pipe)& transport" "permitted commands"
-The string is expanded, and is then interpreted as a colon-separated list of
-permitted commands. If &%restrict_to_path%& is not set, the only commands
-permitted are those in the &%allow_commands%& list. They need not be absolute
-paths; the &%path%& option is still used for relative paths. If
-&%restrict_to_path%& is set with &%allow_commands%&, the command must either be
-in the &%allow_commands%& list, or a name without any slashes that is found on
-the path. In other words, if neither &%allow_commands%& nor
-&%restrict_to_path%& is set, there is no restriction on the command, but
-otherwise only commands that are permitted by one or the other are allowed. For
-example, if
-.code
-allow_commands = /usr/bin/vacation
-.endd
-and &%restrict_to_path%& is not set, the only permitted command is
-&_/usr/bin/vacation_&. The &%allow_commands%& option may not be set if
-&%use_shell%& is set.
-
-
-.option batch_id pipe string&!! unset
-See the description of local delivery batching in chapter &<<CHAPbatching>>&.
-
-
-.option batch_max pipe integer 1
-This limits the number of addresses that can be handled in a single delivery.
-See the description of local delivery batching in chapter &<<CHAPbatching>>&.
-
-
-.option check_string pipe string unset
-As &(pipe)& writes the message, the start of each line is tested for matching
-&%check_string%&, and if it does, the initial matching characters are replaced
-by the contents of &%escape_string%&, provided both are set. The value of
-&%check_string%& is a literal string, not a regular expression, and the case of
-any letters it contains is significant. When &%use_bsmtp%& is set, the contents
-of &%check_string%& and &%escape_string%& are forced to values that implement
-the SMTP escaping protocol. Any settings made in the configuration file are
-ignored.
-
-
-.option command pipe string&!! unset
-This option need not be set when &(pipe)& is being used to deliver to pipes
-obtained directly from address redirections. In other cases, the option must be
-set, to provide a command to be run. It need not yield an absolute path (see
-the &%path%& option below). The command is split up into separate arguments by
-Exim, and each argument is separately expanded, as described in section
-&<<SECThowcommandrun>>& above.
-
-
-.option environment pipe string&!! unset
-.cindex "&(pipe)& transport" "environment for command"
-.cindex "environment" "&(pipe)& transport"
-This option is used to add additional variables to the environment in which the
-command runs (see section &<<SECTpipeenv>>& for the default list). Its value is
-a string which is expanded, and then interpreted as a colon-separated list of
-environment settings of the form <&'name'&>=<&'value'&>.
-
-
-.option escape_string pipe string unset
-See &%check_string%& above.
-
-
-.option freeze_exec_fail pipe boolean false
-.cindex "exec failure"
-.cindex "failure of exec"
-.cindex "&(pipe)& transport" "failure of exec"
-Failure to exec the command in a pipe transport is by default treated like
-any other failure while running the command. However, if &%freeze_exec_fail%&
-is set, failure to exec is treated specially, and causes the message to be
-frozen, whatever the setting of &%ignore_status%&.
-
-
-.option freeze_signal pipe boolean false
-.cindex "signal exit"
-.cindex "&(pipe)& transport", "signal exit"
-Normally if the process run by a command in a pipe transport exits on a signal,
-a bounce message is sent. If &%freeze_signal%& is set, the message will be
-frozen in Exim's queue instead.
-
-
-.option force_command pipe boolean false
-.cindex "force command"
-.cindex "&(pipe)& transport", "force command"
-Normally when a router redirects an address directly to a pipe command
-the &%command%& option on the transport is ignored.  If &%force_command%&
-is set, the &%command%& option will used. This is especially
-useful for forcing a wrapper or additional argument to be added to the
-command. For example:
-.code
-command = /usr/bin/remote_exec myhost -- $address_pipe
-force_command
-.endd
-
-Note that &$address_pipe$& is handled specially in &%command%& when
-&%force_command%& is set, expanding out to the original argument vector as
-separate items, similarly to a Unix shell &`"$@"`& construct.
-
-
-.option ignore_status pipe boolean false
-If this option is true, the status returned by the subprocess that is set up to
-run the command is ignored, and Exim behaves as if zero had been returned.
-Otherwise, a non-zero status or termination by signal causes an error return
-from the transport unless the status value is one of those listed in
-&%temp_errors%&; these cause the delivery to be deferred and tried again later.
-
-&*Note*&: This option does not apply to timeouts, which do not return a status.
-See the &%timeout_defer%& option for how timeouts are handled.
-
-
-.option log_defer_output pipe boolean false
-.cindex "&(pipe)& transport" "logging output"
-If this option is set, and the status returned by the command is
-one of the codes listed in &%temp_errors%& (that is, delivery was deferred),
-and any output was produced on stdout or stderr, the first line of it is
-written to the main log.
-
-
-.option log_fail_output pipe boolean false
-If this option is set, and the command returns any output on stdout or
-stderr, and also ends with a return code that is neither zero nor one of
-the return codes listed in &%temp_errors%& (that is, the delivery
-failed), the first line of output is written to the main log. This
-option and &%log_output%& are mutually exclusive.  Only one of them may
-be set.
-
-
-.option log_output pipe boolean false
-If this option is set and the command returns any output on stdout or
-stderr, the first line of output is written to the main log, whatever
-the return code. This option and &%log_fail_output%& are mutually
-exclusive. Only one of them may be set.
-
-
-.option max_output pipe integer 20K
-This specifies the maximum amount of output that the command may produce on its
-standard output and standard error file combined. If the limit is exceeded, the
-process running the command is killed. This is intended as a safety measure to
-catch runaway processes. The limit is applied independently of the settings of
-the options that control what is done with such output (for example,
-&%return_output%&). Because of buffering effects, the amount of output may
-exceed the limit by a small amount before Exim notices.
-
-
-.option message_prefix pipe string&!! "see below"
-The string specified here is expanded and output at the start of every message.
-The default is unset if &%use_bsmtp%& is set. Otherwise it is
-.code
-message_prefix = \
-  From ${if def:return_path{$return_path}{MAILER-DAEMON}}\
-  ${tod_bsdinbox}\n
-.endd
-.cindex "Cyrus"
-.cindex "&%tmail%&"
-.cindex "&""From""& line"
-This is required by the commonly used &_/usr/bin/vacation_& program.
-However, it must &'not'& be present if delivery is to the Cyrus IMAP server,
-or to the &%tmail%& local delivery agent. The prefix can be suppressed by
-setting
-.code
-message_prefix =
-.endd
-&*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
-&`\n`& to &`\r\n`& in &%message_prefix%&.
-
-
-.option message_suffix pipe string&!! "see below"
-The string specified here is expanded and output at the end of every message.
-The default is unset if &%use_bsmtp%& is set. Otherwise it is a single newline.
-The suffix can be suppressed by setting
-.code
-message_suffix =
-.endd
-&*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
-&`\n`& to &`\r\n`& in &%message_suffix%&.
-
-
-.option path pipe string&!! "/bin:/usr/bin"
-This option is expanded and
-specifies the string that is set up in the PATH environment
-variable of the subprocess.
-If the &%command%& option does not yield an absolute path name, the command is
-sought in the PATH directories, in the usual way. &*Warning*&: This does not
-apply to a command specified as a transport filter.
-
-
-.option permit_coredump pipe boolean false
-Normally Exim inhibits core-dumps during delivery.  If you have a need to get
-a core-dump of a pipe command, enable this command.  This enables core-dumps
-during delivery and affects both the Exim binary and the pipe command run.
-It is recommended that this option remain off unless and until you have a need
-for it and that this only be enabled when needed, as the risk of excessive
-resource consumption can be quite high.  Note also that Exim is typically
-installed as a setuid binary and most operating systems will inhibit coredumps
-of these by default, so further OS-specific action may be required.
-
-
-.option pipe_as_creator pipe boolean false
-.cindex "uid (user id)" "local delivery"
-If the generic &%user%& option is not set and this option is true, the delivery
-process is run under the uid that was in force when Exim was originally called
-to accept the message. If the group id is not otherwise set (via the generic
-&%group%& option), the gid that was in force when Exim was originally called to
-accept the message is used.
-
-
-.option restrict_to_path pipe boolean false
-When this option is set, any command name not listed in &%allow_commands%& must
-contain no slashes. The command is searched for only in the directories listed
-in the &%path%& option. This option is intended for use in the case when a pipe
-command has been generated from a user's &_.forward_& file. This is usually
-handled by a &(pipe)& transport called &%address_pipe%&.
-
-
-.option return_fail_output pipe boolean false
-If this option is true, and the command produced any output and ended with a
-return code other than zero or one of the codes listed in &%temp_errors%& (that
-is, the delivery failed), the output is returned in the bounce message.
-However, if the message has a null sender (that is, it is itself a bounce
-message), output from the command is discarded. This option and
-&%return_output%& are mutually exclusive. Only one of them may be set.
-
-
-
-.option return_output pipe boolean false
-If this option is true, and the command produced any output, the delivery is
-deemed to have failed whatever the return code from the command, and the output
-is returned in the bounce message. Otherwise, the output is just discarded.
-However, if the message has a null sender (that is, it is a bounce message),
-output from the command is always discarded, whatever the setting of this
-option. This option and &%return_fail_output%& are mutually exclusive. Only one
-of them may be set.
-
-
-
-.option temp_errors pipe "string list" "see below"
-.cindex "&(pipe)& transport" "temporary failure"
-This option contains either a colon-separated list of numbers, or a single
-asterisk. If &%ignore_status%& is false
-and &%return_output%& is not set,
-and the command exits with a non-zero return code, the failure is treated as
-temporary and the delivery is deferred if the return code matches one of the
-numbers, or if the setting is a single asterisk. Otherwise, non-zero return
-codes are treated as permanent errors. The default setting contains the codes
-defined by EX_TEMPFAIL and EX_CANTCREAT in &_sysexits.h_&. If Exim is
-compiled on a system that does not define these macros, it assumes values of 75
-and 73, respectively.
-
-
-.option timeout pipe time 1h
-If the command fails to complete within this time, it is killed. This normally
-causes the delivery to fail (but see &%timeout_defer%&). A zero time interval
-specifies no timeout. In order to ensure that any subprocesses created by the
-command are also killed, Exim makes the initial process a process group leader,
-and kills the whole process group on a timeout. However, this can be defeated
-if one of the processes starts a new process group.
-
-.option timeout_defer pipe boolean false
-A timeout in a &(pipe)& transport, either in the command that the transport
-runs, or in a transport filter that is associated with it, is by default
-treated as a hard error, and the delivery fails. However, if &%timeout_defer%&
-is set true, both kinds of timeout become temporary errors, causing the
-delivery to be deferred.
-
-.option umask pipe "octal integer" 022
-This specifies the umask setting for the subprocess that runs the command.
-
-
-.option use_bsmtp pipe boolean false
-.cindex "envelope sender"
-If this option is set true, the &(pipe)& transport writes messages in &"batch
-SMTP"& format, with the envelope sender and recipient(s) included as SMTP
-commands. If you want to include a leading HELO command with such messages,
-you can do so by setting the &%message_prefix%& option. See section
-&<<SECTbatchSMTP>>& for details of batch SMTP.
-
-.option use_classresources pipe boolean false
-.cindex "class resources (BSD)"
-This option is available only when Exim is running on FreeBSD, NetBSD, or
-BSD/OS. If it is set true, the &[setclassresources()]& function is used to set
-resource limits when a &(pipe)& transport is run to perform a delivery. The
-limits for the uid under which the pipe is to run are obtained from the login
-class database.
-
-
-.option use_crlf pipe boolean false
-.cindex "carriage return"
-.cindex "linefeed"
-This option causes lines to be terminated with the two-character CRLF sequence
-(carriage return, linefeed) instead of just a linefeed character. In the case
-of batched SMTP, the byte sequence written to the pipe is then an exact image
-of what would be sent down a real SMTP connection.
-
-The contents of the &%message_prefix%& and &%message_suffix%& options are
-written verbatim, so must contain their own carriage return characters if these
-are needed. When &%use_bsmtp%& is not set, the default values for both
-&%message_prefix%& and &%message_suffix%& end with a single linefeed, so their
-values must be changed to end with &`\r\n`& if &%use_crlf%& is set.
-
-
-.option use_shell pipe boolean false
-.vindex "&$pipe_addresses$&"
-If this option is set, it causes the command to be passed to &_/bin/sh_&
-instead of being run directly from the transport, as described in section
-&<<SECThowcommandrun>>&. This is less secure, but is needed in some situations
-where the command is expected to be run under a shell and cannot easily be
-modified. The &%allow_commands%& and &%restrict_to_path%& options, and the
-&`$pipe_addresses`& facility are incompatible with &%use_shell%&. The
-command is expanded as a single string, and handed to &_/bin/sh_& as data for
-its &%-c%& option.
-
-
-
-.section "Using an external local delivery agent" "SECID143"
-.cindex "local delivery" "using an external agent"
-.cindex "&'procmail'&"
-.cindex "external local delivery"
-.cindex "delivery" "&'procmail'&"
-.cindex "delivery" "by external agent"
-The &(pipe)& transport can be used to pass all messages that require local
-delivery to a separate local delivery agent such as &%procmail%&. When doing
-this, care must be taken to ensure that the pipe is run under an appropriate
-uid and gid. In some configurations one wants this to be a uid that is trusted
-by the delivery agent to supply the correct sender of the message. It may be
-necessary to recompile or reconfigure the delivery agent so that it trusts an
-appropriate user. The following is an example transport and router
-configuration for &%procmail%&:
-.code
-# transport
-procmail_pipe:
-  driver = pipe
-  command = /usr/local/bin/procmail -d $local_part
-  return_path_add
-  delivery_date_add
-  envelope_to_add
-  check_string = "From "
-  escape_string = ">From "
-  umask = 077
-  user = $local_part
-  group = mail
-
-# router
-procmail:
-  driver = accept
-  check_local_user
-  transport = procmail_pipe
-.endd
-In this example, the pipe is run as the local user, but with the group set to
-&'mail'&. An alternative is to run the pipe as a specific user such as &'mail'&
-or &'exim'&, but in this case you must arrange for &%procmail%& to trust that
-user to supply a correct sender address. If you do not specify either a
-&%group%& or a &%user%& option, the pipe command is run as the local user. The
-home directory is the user's home directory by default.
-
-&*Note*&: The command that the pipe transport runs does &'not'& begin with
-.code
-IFS=" "
-.endd
-as shown in some &%procmail%& documentation, because Exim does not by default
-use a shell to run pipe commands.
-
-.cindex "Cyrus"
-The next example shows a transport and a router for a system where local
-deliveries are handled by the Cyrus IMAP server.
-.code
-# transport
-local_delivery_cyrus:
-  driver = pipe
-  command = /usr/cyrus/bin/deliver \
-            -m ${substr_1:$local_part_suffix} -- $local_part
-  user = cyrus
-  group = mail
-  return_output
-  log_output
-  message_prefix =
-  message_suffix =
-
-# router
-local_user_cyrus:
-  driver = accept
-  check_local_user
-  local_part_suffix = .*
-  transport = local_delivery_cyrus
-.endd
-Note the unsetting of &%message_prefix%& and &%message_suffix%&, and the use of
-&%return_output%& to cause any text written by Cyrus to be returned to the
-sender.
-.ecindex IIDpiptra1
-.ecindex IIDpiptra2
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "The smtp transport" "CHAPsmtptrans"
-.scindex IIDsmttra1 "transports" "&(smtp)&"
-.scindex IIDsmttra2 "&(smtp)& transport"
-The &(smtp)& transport delivers messages over TCP/IP connections using the SMTP
-or LMTP protocol. The list of hosts to try can either be taken from the address
-that is being processed (having been set up by the router), or specified
-explicitly for the transport. Timeout and retry processing (see chapter
-&<<CHAPretry>>&) is applied to each IP address independently.
-
-
-.section "Multiple messages on a single connection" "SECID144"
-The sending of multiple messages over a single TCP/IP connection can arise in
-two ways:
-
-.ilist
-If a message contains more than &%max_rcpt%& (see below) addresses that are
-routed to the same host, more than one copy of the message has to be sent to
-that host. In this situation, multiple copies may be sent in a single run of
-the &(smtp)& transport over a single TCP/IP connection. (What Exim actually
-does when it has too many addresses to send in one message also depends on the
-value of the global &%remote_max_parallel%& option. Details are given in
-section &<<SECToutSMTPTCP>>&.)
-.next
-.cindex "hints database" "remembering routing"
-When a message has been successfully delivered over a TCP/IP connection, Exim
-looks in its hints database to see if there are any other messages awaiting a
-connection to the same host. If there are, a new delivery process is started
-for one of them, and the current TCP/IP connection is passed on to it. The new
-process may in turn send multiple copies and possibly create yet another
-process.
-.endlist
-
-
-For each copy sent over the same TCP/IP connection, a sequence counter is
-incremented, and if it ever gets to the value of &%connection_max_messages%&,
-no further messages are sent over that connection.
-
-
-
-.section "Use of the $host and $host_address variables" "SECID145"
-.vindex "&$host$&"
-.vindex "&$host_address$&"
-At the start of a run of the &(smtp)& transport, the values of &$host$& and
-&$host_address$& are the name and IP address of the first host on the host list
-passed by the router. However, when the transport is about to connect to a
-specific host, and while it is connected to that host, &$host$& and
-&$host_address$& are set to the values for that host. These are the values
-that are in force when the &%helo_data%&, &%hosts_try_auth%&, &%interface%&,
-&%serialize_hosts%&, and the various TLS options are expanded.
-
-
-.section "Use of $tls_cipher and $tls_peerdn" "usecippeer"
-.vindex &$tls_bits$&
-.vindex &$tls_cipher$&
-.vindex &$tls_peerdn$&
-.vindex &$tls_sni$&
-At the start of a run of the &(smtp)& transport, the values of &$tls_bits$&,
-&$tls_cipher$&, &$tls_peerdn$& and &$tls_sni$&
-are the values that were set when the message was received.
-These are the values that are used for options that are expanded before any
-SMTP connections are made. Just before each connection is made, these four
-variables are emptied. If TLS is subsequently started, they are set to the
-appropriate values for the outgoing connection, and these are the values that
-are in force when any authenticators are run and when the
-&%authenticated_sender%& option is expanded.
-
-These variables are deprecated in favour of &$tls_in_cipher$& et. al.
-and will be removed in a future release.
-
-
-.section "Private options for smtp" "SECID146"
-.cindex "options" "&(smtp)& transport"
-The private options of the &(smtp)& transport are as follows:
-
-
-.option address_retry_include_sender smtp boolean true
-.cindex "4&'xx'& responses" "retrying after"
-When an address is delayed because of a 4&'xx'& response to a RCPT command, it
-is the combination of sender and recipient that is delayed in subsequent queue
-runs until the retry time is reached. You can delay the recipient without
-reference to the sender (which is what earlier versions of Exim did), by
-setting &%address_retry_include_sender%& false. However, this can lead to
-problems with servers that regularly issue 4&'xx'& responses to RCPT commands.
-
-.option allow_localhost smtp boolean false
-.cindex "local host" "sending to"
-.cindex "fallback" "hosts specified on transport"
-When a host specified in &%hosts%& or &%fallback_hosts%& (see below) turns out
-to be the local host, or is listed in &%hosts_treat_as_local%&, delivery is
-deferred by default. However, if &%allow_localhost%& is set, Exim goes on to do
-the delivery anyway. This should be used only in special cases when the
-configuration ensures that no looping will result (for example, a differently
-configured Exim is listening on the port to which the message is sent).
-
-
-.option authenticated_sender smtp string&!! unset
-.cindex "Cyrus"
-When Exim has authenticated as a client, or if &%authenticated_sender_force%&
-is true, this option sets a value for the AUTH= item on outgoing MAIL commands,
-overriding any existing authenticated sender value. If the string expansion is
-forced to fail, the option is ignored. Other expansion failures cause delivery
-to be deferred. If the result of expansion is an empty string, that is also
-ignored.
-
-The expansion happens after the outgoing connection has been made and TLS
-started, if required. This means that the &$host$&, &$host_address$&,
-&$tls_out_cipher$&, and &$tls_out_peerdn$& variables are set according to the
-particular connection.
-
-If the SMTP session is not authenticated, the expansion of
-&%authenticated_sender%& still happens (and can cause the delivery to be
-deferred if it fails), but no AUTH= item is added to MAIL commands
-unless &%authenticated_sender_force%& is true.
-
-This option allows you to use the &(smtp)& transport in LMTP mode to
-deliver mail to Cyrus IMAP and provide the proper local part as the
-&"authenticated sender"&, via a setting such as:
-.code
-authenticated_sender = $local_part
-.endd
-This removes the need for IMAP subfolders to be assigned special ACLs to
-allow direct delivery to those subfolders.
-
-Because of expected uses such as that just described for Cyrus (when no
-domain is involved), there is no checking on the syntax of the provided
-value.
-
-
-.option authenticated_sender_force smtp boolean false
-If this option is set true, the &%authenticated_sender%& option's value
-is used for the AUTH= item on outgoing MAIL commands, even if Exim has not
-authenticated as a client.
-
-
-.option command_timeout smtp time 5m
-This sets a timeout for receiving a response to an SMTP command that has been
-sent out. It is also used when waiting for the initial banner line from the
-remote host. Its value must not be zero.
-
-
-.option connect_timeout smtp time 5m
-This sets a timeout for the &[connect()]& function, which sets up a TCP/IP call
-to a remote host. A setting of zero allows the system timeout (typically
-several minutes) to act. To have any effect, the value of this option must be
-less than the system timeout. However, it has been observed that on some
-systems there is no system timeout, which is why the default value for this
-option is 5 minutes, a value recommended by RFC 1123.
-
-
-.option connection_max_messages smtp integer 500
-.cindex "SMTP" "passed connection"
-.cindex "SMTP" "multiple deliveries"
-.cindex "multiple SMTP deliveries"
-This controls the maximum number of separate message deliveries that are sent
-over a single TCP/IP connection. If the value is zero, there is no limit.
-For testing purposes, this value can be overridden by the &%-oB%& command line
-option.
-
-
-.option dane_require_tls_ciphers smtp string&!! unset
-.cindex "TLS" "requiring specific ciphers for DANE"
-.cindex "cipher" "requiring specific"
-.cindex DANE "TLS ciphers"
-This option may be used to override &%tls_require_ciphers%& for connections
-where DANE has been determined to be in effect.
-If not set, then &%tls_require_ciphers%& will be used.
-Normal SMTP delivery is not able to make strong demands of TLS cipher
-configuration, because delivery will fall back to plaintext.  Once DANE has
-been determined to be in effect, there is no plaintext fallback and making the
-TLS cipherlist configuration stronger will increase security, rather than
-counter-intuitively decreasing it.
-If the option expands to be empty or is forced to fail, then it will
-be treated as unset and &%tls_require_ciphers%& will be used instead.
-
-
-.option data_timeout smtp time 5m
-This sets a timeout for the transmission of each block in the data portion of
-the message. As a result, the overall timeout for a message depends on the size
-of the message. Its value must not be zero. See also &%final_timeout%&.
-
-
-.option dkim_canon smtp string&!! unset
-DKIM signing option.  For details see section &<<SECDKIMSIGN>>&.
-.option dkim_domain smtp string list&!! unset
-DKIM signing option.  For details see section &<<SECDKIMSIGN>>&.
-.option dkim_hash smtp string&!! sha256
-DKIM signing option.  For details see section &<<SECDKIMSIGN>>&.
-.option dkim_identity smtp string&!! unset
-DKIM signing option.  For details see section &<<SECDKIMSIGN>>&.
-.option dkim_private_key smtp string&!! unset
-DKIM signing option.  For details see section &<<SECDKIMSIGN>>&.
-.option dkim_selector smtp string&!! unset
-DKIM signing option.  For details see section &<<SECDKIMSIGN>>&.
-.option dkim_strict smtp string&!! unset
-DKIM signing option.  For details see section &<<SECDKIMSIGN>>&.
-.option dkim_sign_headers smtp string&!! "per RFC"
-DKIM signing option.  For details see section &<<SECDKIMSIGN>>&.
-.option dkim_timestamps smtp string&!! unset
-DKIM signing option.  For details see section &<<SECDKIMSIGN>>&.
-
-
-.option delay_after_cutoff smtp boolean true
-.cindex "final cutoff" "retries, controlling"
-.cindex retry "final cutoff"
-This option controls what happens when all remote IP addresses for a given
-domain have been inaccessible for so long that they have passed their retry
-cutoff times.
-
-In the default state, if the next retry time has not been reached for any of
-them, the address is bounced without trying any deliveries. In other words,
-Exim delays retrying an IP address after the final cutoff time until a new
-retry time is reached, and can therefore bounce an address without ever trying
-a delivery, when machines have been down for a long time. Some people are
-unhappy at this prospect, so...
-
-If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
-addresses are past their final cutoff time, Exim tries to deliver to those
-IP addresses that have not been tried since the message arrived. If there are
-none, of if they all fail, the address is bounced. In other words, it does not
-delay when a new message arrives, but immediately tries those expired IP
-addresses that haven't been tried since the message arrived. If there is a
-continuous stream of messages for the dead hosts, unsetting
-&%delay_after_cutoff%& means that there will be many more attempts to deliver
-to them.
-
-
-.option dns_qualify_single smtp boolean true
-If the &%hosts%& or &%fallback_hosts%& option is being used,
-and the &%gethostbyname%& option is false,
-the RES_DEFNAMES resolver option is set. See the &%qualify_single%& option
-in chapter &<<CHAPdnslookup>>& for more details.
-
-
-.option dns_search_parents smtp boolean false
-If the &%hosts%& or &%fallback_hosts%& option is being used, and the
-&%gethostbyname%& option is false, the RES_DNSRCH resolver option is set.
-See the &%search_parents%& option in chapter &<<CHAPdnslookup>>& for more
-details.
-
-
-.option dnssec_request_domains smtp "domain list&!!" *
-.cindex "MX record" "security"
-.cindex "DNSSEC" "MX lookup"
-.cindex "security" "MX lookup"
-.cindex "DNS" "DNSSEC"
-DNS lookups for domains matching &%dnssec_request_domains%& will be done with
-the dnssec request bit set. Setting this transport option is only useful if the
-transport overrides or sets the host names. See the &%dnssec_request_domains%&
-router option.
-
-
-
-.option dnssec_require_domains smtp "domain list&!!" unset
-.cindex "MX record" "security"
-.cindex "DNSSEC" "MX lookup"
-.cindex "security" "MX lookup"
-.cindex "DNS" "DNSSEC"
-DNS lookups for domains matching &%dnssec_require_domains%& will be done with
-the dnssec request bit set.  Setting this transport option is only
-useful if the transport overrides or sets the host names. See the
-&%dnssec_require_domains%& router option.
-
-
-
-.option dscp smtp string&!! unset
-.cindex "DCSP" "outbound"
-This option causes the DSCP value associated with a socket to be set to one
-of a number of fixed strings or to numeric value.
-The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
-Common values include &`throughput`&, &`mincost`&, and on newer systems
-&`ef`&, &`af41`&, etc.  Numeric values may be in the range 0 to 0x3F.
-
-The outbound packets from Exim will be marked with this value in the header
-(for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
-that these values will have any effect, not be stripped by networking
-equipment, or do much of anything without cooperation with your Network
-Engineer and those of all network operators between the source and destination.
-
-
-.option fallback_hosts smtp "string list" unset
-.cindex "fallback" "hosts specified on transport"
-String expansion is not applied to this option. The argument must be a
-colon-separated list of host names or IP addresses, optionally also including
-port numbers, though the separator can be changed, as described in section
-&<<SECTlistconstruct>>&. Each individual item in the list is the same as an
-item in a &%route_list%& setting for the &(manualroute)& router, as described
-in section &<<SECTformatonehostitem>>&.
-
-Fallback hosts can also be specified on routers, which associate them with the
-addresses they process. As for the &%hosts%& option without &%hosts_override%&,
-&%fallback_hosts%& specified on the transport is used only if the address does
-not have its own associated fallback host list. Unlike &%hosts%&, a setting of
-&%fallback_hosts%& on an address is not overridden by &%hosts_override%&.
-However, &%hosts_randomize%& does apply to fallback host lists.
-
-If Exim is unable to deliver to any of the hosts for a particular address, and
-the errors are not permanent rejections, the address is put on a separate
-transport queue with its host list replaced by the fallback hosts, unless the
-address was routed via MX records and the current host was in the original MX
-list. In that situation, the fallback host list is not used.
-
-Once normal deliveries are complete, the fallback queue is delivered by
-re-running the same transports with the new host lists. If several failing
-addresses have the same fallback hosts (and &%max_rcpt%& permits it), a single
-copy of the message is sent.
-
-The resolution of the host names on the fallback list is controlled by the
-&%gethostbyname%& option, as for the &%hosts%& option. Fallback hosts apply
-both to cases when the host list comes with the address and when it is taken
-from &%hosts%&. This option provides a &"use a smart host only if delivery
-fails"& facility.
-
-
-.option final_timeout smtp time 10m
-This is the timeout that applies while waiting for the response to the final
-line containing just &"."& that terminates a message. Its value must not be
-zero.
-
-.option gethostbyname smtp boolean false
-If this option is true when the &%hosts%& and/or &%fallback_hosts%& options are
-being used, names are looked up using &[gethostbyname()]&
-(or &[getipnodebyname()]& when available)
-instead of using the DNS. Of course, that function may in fact use the DNS, but
-it may also consult other sources of information such as &_/etc/hosts_&.
-
-.option gnutls_compat_mode smtp boolean unset
-This option controls whether GnuTLS is used in compatibility mode in an Exim
-server. This reduces security slightly, but improves interworking with older
-implementations of TLS.
-
-.option helo_data smtp string&!! "see below"
-.cindex "HELO" "argument, setting"
-.cindex "EHLO" "argument, setting"
-.cindex "LHLO argument setting"
-The value of this option is expanded after a connection to a another host has
-been set up. The result is used as the argument for the EHLO, HELO, or LHLO
-command that starts the outgoing SMTP or LMTP session. The default value of the
-option is:
-.code
-$primary_hostname
-.endd
-During the expansion, the variables &$host$& and &$host_address$& are set to
-the identity of the remote host, and the variables &$sending_ip_address$& and
-&$sending_port$& are set to the local IP address and port number that are being
-used. These variables can be used to generate different values for different
-servers or different local IP addresses. For example, if you want the string
-that is used for &%helo_data%& to be obtained by a DNS lookup of the outgoing
-interface address, you could use this:
-.code
-helo_data = ${lookup dnsdb{ptr=$sending_ip_address}{$value}\
-  {$primary_hostname}}
-.endd
-The use of &%helo_data%& applies both to sending messages and when doing
-callouts.
-
-.option hosts smtp "string list&!!" unset
-Hosts are associated with an address by a router such as &(dnslookup)&, which
-finds the hosts by looking up the address domain in the DNS, or by
-&(manualroute)&, which has lists of hosts in its configuration. However,
-email addresses can be passed to the &(smtp)& transport by any router, and not
-all of them can provide an associated list of hosts.
-
-The &%hosts%& option specifies a list of hosts to be used if the address being
-processed does not have any hosts associated with it. The hosts specified by
-&%hosts%& are also used, whether or not the address has its own hosts, if
-&%hosts_override%& is set.
-
-The string is first expanded, before being interpreted as a colon-separated
-list of host names or IP addresses, possibly including port numbers. The
-separator may be changed to something other than colon, as described in section
-&<<SECTlistconstruct>>&. Each individual item in the list is the same as an
-item in a &%route_list%& setting for the &(manualroute)& router, as described
-in section &<<SECTformatonehostitem>>&. However, note that the &`/MX`& facility
-of the &(manualroute)& router is not available here.
-
-If the expansion fails, delivery is deferred. Unless the failure was caused by
-the inability to complete a lookup, the error is logged to the panic log as
-well as the main log. Host names are looked up either by searching directly for
-address records in the DNS or by calling &[gethostbyname()]& (or
-&[getipnodebyname()]& when available), depending on the setting of the
-&%gethostbyname%& option. When Exim is compiled with IPv6 support, if a host
-that is looked up in the DNS has both IPv4 and IPv6 addresses, both types of
-address are used.
-
-During delivery, the hosts are tried in order, subject to their retry status,
-unless &%hosts_randomize%& is set.
-
-
-.option hosts_avoid_esmtp smtp "host list&!!" unset
-.cindex "ESMTP, avoiding use of"
-.cindex "HELO" "forcing use of"
-.cindex "EHLO" "avoiding use of"
-.cindex "PIPELINING" "avoiding the use of"
-This option is for use with broken hosts that announce ESMTP facilities (for
-example, PIPELINING) and then fail to implement them properly. When a host
-matches &%hosts_avoid_esmtp%&, Exim sends HELO rather than EHLO at the
-start of the SMTP session. This means that it cannot use any of the ESMTP
-facilities such as AUTH, PIPELINING, SIZE, and STARTTLS.
-
-
-.option hosts_avoid_pipelining smtp "host list&!!" unset
-.cindex "PIPELINING" "avoiding the use of"
-Exim will not use the SMTP PIPELINING extension when delivering to any host
-that matches this list, even if the server host advertises PIPELINING support.
-
-.option hosts_pipe_connect smtp "host list&!!" unset
-.cindex "pipelining" "early connection"
-.cindex "pipelining" PIPE_CONNECT
-If Exim is built with the SUPPORT_PIPE_CONNECT build option
-this option controls which to hosts the facility watched for
-and recorded, and used for subsequent connections.
-
-The retry hints database is used for the record,
-and records are subject to the &%retry_data_expire%& option.
-When used, the pipelining saves on roundtrip times.
-It also turns SMTP into a client-first protocol
-so combines well with TCP Fast Open.
-
-See also the &%pipelining_connect_advertise_hosts%& main option.
-
-Note:
-When the facility is used, the transport &%helo_data%& option
-will be expanded before the &$sending_ip_address$& variable
-is filled in.
-A check is made for the use of that variable, without the
-presence of a &"def:"& test on it, but suitably complex coding
-can avoid the check and produce unexpected results.
-You have been warned.
-
-
-.option hosts_avoid_tls smtp "host list&!!" unset
-.cindex "TLS" "avoiding for certain hosts"
-Exim will not try to start a TLS session when delivering to any host that
-matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
-
-.option hosts_verify_avoid_tls smtp "host list&!!" unset
-.cindex "TLS" "avoiding for certain hosts"
-Exim will not try to start a TLS session for a verify callout,
-or when delivering in cutthrough mode,
-to any host that matches this list.
-
-
-.option hosts_max_try smtp integer 5
-.cindex "host" "maximum number to try"
-.cindex "limit" "number of hosts tried"
-.cindex "limit" "number of MX tried"
-.cindex "MX record" "maximum tried"
-This option limits the number of IP addresses that are tried for any one
-delivery in cases where there are temporary delivery errors. Section
-&<<SECTvalhosmax>>& describes in detail how the value of this option is used.
-
-
-.option hosts_max_try_hardlimit smtp integer 50
-This is an additional check on the maximum number of IP addresses that Exim
-tries for any one delivery. Section &<<SECTvalhosmax>>& describes its use and
-why it exists.
-
-
-
-.option hosts_nopass_tls smtp "host list&!!" unset
-.cindex "TLS" "passing connection"
-.cindex "multiple SMTP deliveries"
-.cindex "TLS" "multiple message deliveries"
-For any host that matches this list, a connection on which a TLS session has
-been started will not be passed to a new delivery process for sending another
-message on the same connection. See section &<<SECTmulmessam>>& for an
-explanation of when this might be needed.
-
-.option hosts_noproxy_tls smtp "host list&!!" unset
-.cindex "TLS" "passing connection"
-.cindex "multiple SMTP deliveries"
-.cindex "TLS" "multiple message deliveries"
-For any host that matches this list, a TLS session which has
-been started will not be passed to a new delivery process for sending another
-message on the same session.
-
-The traditional implementation closes down TLS and re-starts it in the new
-process, on the same open TCP connection, for each successive message
-sent.  If permitted by this option a pipe to to the new process is set up
-instead, and the original process maintains the TLS connection and proxies
-the SMTP connection from and to the new process and any subsequents.
-The new process has no access to TLS information, so cannot include it in
-logging.
-
-
-
-.option hosts_override smtp boolean false
-If this option is set and the &%hosts%& option is also set, any hosts that are
-attached to the address are ignored, and instead the hosts specified by the
-&%hosts%& option are always used. This option does not apply to
-&%fallback_hosts%&.
-
-
-.option hosts_randomize smtp boolean false
-.cindex "randomized host list"
-.cindex "host" "list of; randomized"
-.cindex "fallback" "randomized hosts"
-If this option is set, and either the list of hosts is taken from the
-&%hosts%& or the &%fallback_hosts%& option, or the hosts supplied by the router
-were not obtained from MX records (this includes fallback hosts from the
-router), and were not randomized by the router, the order of trying the hosts
-is randomized each time the transport runs. Randomizing the order of a host
-list can be used to do crude load sharing.
-
-When &%hosts_randomize%& is true, a host list may be split into groups whose
-order is separately randomized. This makes it possible to set up MX-like
-behaviour. The boundaries between groups are indicated by an item that is just
-&`+`& in the host list. For example:
-.code
-hosts = host1:host2:host3:+:host4:host5
-.endd
-The order of the first three hosts and the order of the last two hosts is
-randomized for each use, but the first three always end up before the last two.
-If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored.
-
-.option hosts_require_auth smtp "host list&!!" unset
-.cindex "authentication" "required by client"
-This option provides a list of servers for which authentication must succeed
-before Exim will try to transfer a message. If authentication fails for
-servers which are not in this list, Exim tries to send unauthenticated. If
-authentication fails for one of these servers, delivery is deferred. This
-temporary error is detectable in the retry rules, so it can be turned into a
-hard failure if required. See also &%hosts_try_auth%&, and chapter
-&<<CHAPSMTPAUTH>>& for details of authentication.
-
-
-.option hosts_request_ocsp smtp "host list&!!" *
-.cindex "TLS" "requiring for certain servers"
-Exim will request a Certificate Status on a
-TLS session for any host that matches this list.
-&%tls_verify_certificates%& should also be set for the transport.
-
-.option hosts_require_dane smtp "host list&!!" unset
-.cindex DANE "transport options"
-.cindex DANE "requiring for certain servers"
-If built with DANE support, Exim  will require that a DNSSEC-validated
-TLSA record is present for any host matching the list,
-and that a DANE-verified TLS connection is made. See
-the &%dnssec_request_domains%& router and transport options.
-There will be no fallback to in-clear communication.
-See section &<<SECDANE>>&.
-
-.option hosts_require_ocsp smtp "host list&!!" unset
-.cindex "TLS" "requiring for certain servers"
-Exim will request, and check for a valid Certificate Status being given, on a
-TLS session for any host that matches this list.
-&%tls_verify_certificates%& should also be set for the transport.
-
-.option hosts_require_tls smtp "host list&!!" unset
-.cindex "TLS" "requiring for certain servers"
-Exim will insist on using a TLS session when delivering to any host that
-matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
-&*Note*&: This option affects outgoing mail only. To insist on TLS for
-incoming messages, use an appropriate ACL.
-
-.option hosts_try_auth smtp "host list&!!" unset
-.cindex "authentication" "optional in client"
-This option provides a list of servers to which, provided they announce
-authentication support, Exim will attempt to authenticate as a client when it
-connects. If authentication fails, Exim will try to transfer the message
-unauthenticated. See also &%hosts_require_auth%&, and chapter
-&<<CHAPSMTPAUTH>>& for details of authentication.
-
-.option hosts_try_chunking smtp "host list&!!" *
-.cindex CHUNKING "enabling, in client"
-.cindex BDAT "SMTP command"
-.cindex "RFC 3030" "CHUNKING"
-This option provides a list of servers to which, provided they announce
-CHUNKING support, Exim will attempt to use BDAT commands rather than DATA.
-.new
-Unless DKIM signing is being done,
-.wen
-BDAT will not be used in conjunction with a transport filter.
-
-.option hosts_try_dane smtp "host list&!!" *
-.cindex DANE "transport options"
-.cindex DANE "attempting for certain servers"
-If built with DANE support, Exim  will require that a DNSSEC-validated
-TLSA record is present for any host matching the list,
-and that a DANE-verified TLS connection is made. See
-the &%dnssec_request_domains%& router and transport options.
-There will be no fallback to in-clear communication.
-See section &<<SECDANE>>&.
-
-.option hosts_try_fastopen smtp "host list&!!" *
-.cindex "fast open, TCP" "enabling, in client"
-.cindex "TCP Fast Open" "enabling, in client"
-.cindex "RFC 7413" "TCP Fast Open"
-This option provides a list of servers to which, provided
-the facility is supported by this system, Exim will attempt to
-perform a TCP Fast Open.
-No data is sent on the SYN segment but, if the remote server also
-supports the facility, it can send its SMTP banner immediately after
-the SYN,ACK segment.  This can save up to one round-trip time.
-
-The facility is only active for previously-contacted servers,
-as the initiator must present a cookie in the SYN segment.
-
-On (at least some) current Linux distributions the facility must be enabled
-in the kernel by the sysadmin before the support is usable.
-There is no option for control of the server side; if the system supports
-it it is always enabled.  Note that lengthy operations in the connect ACL,
-such as DNSBL lookups, will still delay the emission of the SMTP banner.
-
-.option hosts_try_prdr smtp "host list&!!" *
-.cindex "PRDR" "enabling, optional in client"
-This option provides a list of servers to which, provided they announce
-PRDR support, Exim will attempt to negotiate PRDR
-for multi-recipient messages.
-The option can usually be left as default.
-
-.option interface smtp "string list&!!" unset
-.cindex "bind IP address"
-.cindex "IP address" "binding"
-.vindex "&$host$&"
-.vindex "&$host_address$&"
-This option specifies which interface to bind to when making an outgoing SMTP
-call. The value is an IP address, not an interface name such as
-&`eth0`&. Do not confuse this with the interface address that was used when a
-message was received, which is in &$received_ip_address$&, formerly known as
-&$interface_address$&. The name was changed to minimize confusion with the
-outgoing interface address. There is no variable that contains an outgoing
-interface address because, unless it is set by this option, its value is
-unknown.
-
-During the expansion of the &%interface%& option the variables &$host$& and
-&$host_address$& refer to the host to which a connection is about to be made
-during the expansion of the string. Forced expansion failure, or an empty
-string result causes the option to be ignored. Otherwise, after expansion, the
-string must be a list of IP addresses, colon-separated by default, but the
-separator can be changed in the usual way (&<<SECTlistsepchange>>&).
-For example:
-.code
-interface = <; 192.168.123.123 ; 3ffe:ffff:836f::fe86:a061
-.endd
-The first interface of the correct type (IPv4 or IPv6) is used for the outgoing
-connection. If none of them are the correct type, the option is ignored. If
-&%interface%& is not set, or is ignored, the system's IP functions choose which
-interface to use if the host has more than one.
-
-
-.option keepalive smtp boolean true
-.cindex "keepalive" "on outgoing connection"
-This option controls the setting of SO_KEEPALIVE on outgoing TCP/IP socket
-connections. When set, it causes the kernel to probe idle connections
-periodically, by sending packets with &"old"& sequence numbers. The other end
-of the connection should send a acknowledgment if the connection is still okay
-or a reset if the connection has been aborted. The reason for doing this is
-that it has the beneficial effect of freeing up certain types of connection
-that can get stuck when the remote host is disconnected without tidying up the
-TCP/IP call properly. The keepalive mechanism takes several hours to detect
-unreachable hosts.
-
-
-.option lmtp_ignore_quota smtp boolean false
-.cindex "LMTP" "ignoring quota errors"
-If this option is set true when the &%protocol%& option is set to &"lmtp"&, the
-string &`IGNOREQUOTA`& is added to RCPT commands, provided that the LMTP server
-has advertised support for IGNOREQUOTA in its response to the LHLO command.
-
-.option max_rcpt smtp integer 100
-.cindex "RCPT" "maximum number of outgoing"
-This option limits the number of RCPT commands that are sent in a single
-SMTP message transaction. Each set of addresses is treated independently, and
-so can cause parallel connections to the same host if &%remote_max_parallel%&
-permits this.
-
-
-.option multi_domain smtp boolean&!! true
-.vindex "&$domain$&"
-When this option is set, the &(smtp)& transport can handle a number of
-addresses containing a mixture of different domains provided they all resolve
-to the same list of hosts. Turning the option off restricts the transport to
-handling only one domain at a time. This is useful if you want to use
-&$domain$& in an expansion for the transport, because it is set only when there
-is a single domain involved in a remote delivery.
-
-It is expanded per-address and can depend on any of
-&$address_data$&, &$domain_data$&, &$local_part_data$&,
-&$host$&, &$host_address$& and &$host_port$&.
-
-.option port smtp string&!! "see below"
-.cindex "port" "sending TCP/IP"
-.cindex "TCP/IP" "setting outgoing port"
-This option specifies the TCP/IP port on the server to which Exim connects.
-&*Note:*& Do not confuse this with the port that was used when a message was
-received, which is in &$received_port$&, formerly known as &$interface_port$&.
-The name was changed to minimize confusion with the outgoing port. There is no
-variable that contains an outgoing port.
-
-If the value of this option begins with a digit it is taken as a port number;
-otherwise it is looked up using &[getservbyname()]&. The default value is
-normally &"smtp"&,
-but if &%protocol%& is set to &"lmtp"& the default is &"lmtp"&
-and if &%protocol%& is set to &"smtps"& the default is &"smtps"&.
-If the expansion fails, or if a port number cannot be found, delivery
-is deferred.
-
-Note that at least one Linux distribution has been seen failing
-to put &"smtps"& in its &"/etc/services"& file, resulting is such deferrals.
-
-
-
-.option protocol smtp string smtp
-.cindex "LMTP" "over TCP/IP"
-.cindex "ssmtp protocol" "outbound"
-.cindex "TLS" "SSL-on-connect outbound"
-.vindex "&$port$&"
-If this option is set to &"lmtp"& instead of &"smtp"&, the default value for
-the &%port%& option changes to &"lmtp"&, and the transport operates the LMTP
-protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local
-deliveries into closed message stores. Exim also has support for running LMTP
-over a pipe to a local process &-- see chapter &<<CHAPLMTP>>&.
-
-If this option is set to &"smtps"&, the default value for the &%port%& option
-changes to &"smtps"&, and the transport initiates TLS immediately after
-connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade.
-The Internet standards bodies used to strongly discourage use of this mode,
-but as of RFC 8314 it is perferred over STARTTLS for message submission
-(as distinct from MTA-MTA communication).
-
-
-.option retry_include_ip_address smtp boolean&!! true
-Exim normally includes both the host name and the IP address in the key it
-constructs for indexing retry data after a temporary delivery failure. This
-means that when one of several IP addresses for a host is failing, it gets
-tried periodically (controlled by the retry rules), but use of the other IP
-addresses is not affected.
-
-However, in some dialup environments hosts are assigned a different IP address
-each time they connect. In this situation the use of the IP address as part of
-the retry key leads to undesirable behaviour. Setting this option false causes
-Exim to use only the host name.
-Since it is expanded it can be made to depend on the host or domain.
-
-
-.option serialize_hosts smtp "host list&!!" unset
-.cindex "serializing connections"
-.cindex "host" "serializing connections"
-Because Exim operates in a distributed manner, if several messages for the same
-host arrive at around the same time, more than one simultaneous connection to
-the remote host can occur. This is not usually a problem except when there is a
-slow link between the hosts. In that situation it may be helpful to restrict
-Exim to one connection at a time. This can be done by setting
-&%serialize_hosts%& to match the relevant hosts.
-
-.cindex "hints database" "serializing deliveries to a host"
-Exim implements serialization by means of a hints database in which a record is
-written whenever a process connects to one of the restricted hosts. The record
-is deleted when the connection is completed. Obviously there is scope for
-records to get left lying around if there is a system or program crash. To
-guard against this, Exim ignores any records that are more than six hours old.
-
-If you set up this kind of serialization, you should also arrange to delete the
-relevant hints database whenever your system reboots. The names of the files
-start with &_misc_& and they are kept in the &_spool/db_& directory. There
-may be one or two files, depending on the type of DBM in use. The same files
-are used for ETRN serialization.
-
-See also the &%max_parallel%& generic transport option.
-
-
-.option size_addition smtp integer 1024
-.cindex "SMTP" "SIZE"
-.cindex "message" "size issue for transport filter"
-.cindex "size" "of message"
-.cindex "transport" "filter"
-.cindex "filter" "transport filter"
-If a remote SMTP server indicates that it supports the SIZE option of the
-MAIL command, Exim uses this to pass over the message size at the start of
-an SMTP transaction. It adds the value of &%size_addition%& to the value it
-sends, to allow for headers and other text that may be added during delivery by
-configuration options or in a transport filter. It may be necessary to increase
-this if a lot of text is added to messages.
-
-Alternatively, if the value of &%size_addition%& is set negative, it disables
-the use of the SIZE option altogether.
-
-
-.option socks_proxy smtp string&!! unset
-.cindex proxy SOCKS
-This option enables use of SOCKS proxies for connections made by the
-transport.  For details see section &<<SECTproxySOCKS>>&.
-
-
-.option tls_certificate smtp string&!! unset
-.cindex "TLS" "client certificate, location of"
-.cindex "certificate" "client, location of"
-.vindex "&$host$&"
-.vindex "&$host_address$&"
-The value of this option must be the absolute path to a file which contains the
-client's certificate, for possible use when sending a message over an encrypted
-connection. The values of &$host$& and &$host_address$& are set to the name and
-address of the server during the expansion. See chapter &<<CHAPTLS>>& for
-details of TLS.
-
-&*Note*&: This option must be set if you want Exim to be able to use a TLS
-certificate when sending messages as a client. The global option of the same
-name specifies the certificate for Exim as a server; it is not automatically
-assumed that the same certificate should be used when Exim is operating as a
-client.
-
-
-.option tls_crl smtp string&!! unset
-.cindex "TLS" "client certificate revocation list"
-.cindex "certificate" "revocation list for client"
-This option specifies a certificate revocation list. The expanded value must
-be the name of a file that contains a CRL in PEM format.
-
-
-.option tls_dh_min_bits smtp integer 1024
-.cindex "TLS" "Diffie-Hellman minimum acceptable size"
-When establishing a TLS session, if a ciphersuite which uses Diffie-Hellman
-key agreement is negotiated, the server will provide a large prime number
-for use.  This option establishes the minimum acceptable size of that number.
-If the parameter offered by the server is too small, then the TLS handshake
-will fail.
-
-Only supported when using GnuTLS.
-
-
-.option tls_privatekey smtp string&!! unset
-.cindex "TLS" "client private key, location of"
-.vindex "&$host$&"
-.vindex "&$host_address$&"
-The value of this option must be the absolute path to a file which contains the
-client's private key. This is used when sending a message over an encrypted
-connection using a client certificate. The values of &$host$& and
-&$host_address$& are set to the name and address of the server during the
-expansion. If this option is unset, or the expansion is forced to fail, or the
-result is an empty string, the private key is assumed to be in the same file as
-the certificate. See chapter &<<CHAPTLS>>& for details of TLS.
-
-
-.option tls_require_ciphers smtp string&!! unset
-.cindex "TLS" "requiring specific ciphers"
-.cindex "cipher" "requiring specific"
-.vindex "&$host$&"
-.vindex "&$host_address$&"
-The value of this option must be a list of permitted cipher suites, for use
-when setting up an outgoing encrypted connection. (There is a global option of
-the same name for controlling incoming connections.) The values of &$host$& and
-&$host_address$& are set to the name and address of the server during the
-expansion. See chapter &<<CHAPTLS>>& for details of TLS; note that this option
-is used in different ways by OpenSSL and GnuTLS (see sections
-&<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&). For GnuTLS, the order of the
-ciphers is a preference order.
-
-
-
-.option tls_sni smtp string&!! unset
-.cindex "TLS" "Server Name Indication"
-.vindex "&$tls_sni$&"
-If this option is set then it sets the $tls_out_sni variable and causes any
-TLS session to pass this value as the Server Name Indication extension to
-the remote side, which can be used by the remote side to select an appropriate
-certificate and private key for the session.
-
-See &<<SECTtlssni>>& for more information.
-
-Note that for OpenSSL, this feature requires a build of OpenSSL that supports
-TLS extensions.
-
-
-
-
-.option tls_tempfail_tryclear smtp boolean true
-.cindex "4&'xx'& responses" "to STARTTLS"
-When the server host is not in &%hosts_require_tls%&, and there is a problem in
-setting up a TLS session, this option determines whether or not Exim should try
-to deliver the message unencrypted. If it is set false, delivery to the
-current host is deferred; if there are other hosts, they are tried. If this
-option is set true, Exim attempts to deliver unencrypted after a 4&'xx'&
-response to STARTTLS. Also, if STARTTLS is accepted, but the subsequent
-TLS negotiation fails, Exim closes the current connection (because it is in an
-unknown state), opens a new one to the same host, and then tries the delivery
-in clear.
-
-
-.option tls_try_verify_hosts smtp "host list&!!" *
-.cindex "TLS" "server certificate verification"
-.cindex "certificate" "verification of server"
-This option gives a list of hosts for which, on encrypted connections,
-certificate verification will be tried but need not succeed.
-The &%tls_verify_certificates%& option must also be set.
-Note that unless the host is in this list
-TLS connections will be denied to hosts using self-signed certificates
-when &%tls_verify_certificates%& is matched.
-The &$tls_out_certificate_verified$& variable is set when
-certificate verification succeeds.
-
-
-.option tls_verify_cert_hostnames smtp "host list&!!" *
-.cindex "TLS" "server certificate hostname verification"
-.cindex "certificate" "verification of server"
-This option give a list of hosts for which,
-while verifying the server certificate,
-checks will be included on the host name
-(note that this will generally be the result of a DNS MX lookup)
-versus Subject and Subject-Alternate-Name fields.  Wildcard names are permitted
-limited to being the initial component of a 3-or-more component FQDN.
-
-There is no equivalent checking on client certificates.
-
-
-.option tls_verify_certificates smtp string&!! system
-.cindex "TLS" "server certificate verification"
-.cindex "certificate" "verification of server"
-.vindex "&$host$&"
-.vindex "&$host_address$&"
-The value of this option must be either the
-word "system"
-or the absolute path to
-a file or directory containing permitted certificates for servers,
-for use when setting up an encrypted connection.
-
-The "system" value for the option will use a location compiled into the SSL library.
-This is not available for GnuTLS versions preceding 3.0.20; a value of "system"
-is taken as empty and an explicit location
-must be specified.
-
-The use of a directory for the option value is not available for GnuTLS versions
-preceding 3.3.6 and a single file must be used.
-
-With OpenSSL the certificates specified
-explicitly
-either by file or directory
-are added to those given by the system default location.
-
-The values of &$host$& and
-&$host_address$& are set to the name and address of the server during the
-expansion of this option. See chapter &<<CHAPTLS>>& for details of TLS.
-
-For back-compatibility,
-if neither tls_verify_hosts nor tls_try_verify_hosts are set
-(a single-colon empty list counts as being set)
-and certificate verification fails the TLS connection is closed.
-
-
-.option tls_verify_hosts smtp "host list&!!" unset
-.cindex "TLS" "server certificate verification"
-.cindex "certificate" "verification of server"
-This option gives a list of hosts for which, on encrypted connections,
-certificate verification must succeed.
-The &%tls_verify_certificates%& option must also be set.
-If both this option and &%tls_try_verify_hosts%& are unset
-operation is as if this option selected all hosts.
-
-.option utf8_downconvert smtp integer!! unset
-.cindex utf8 "address downconversion"
-.cindex i18n "utf8 address downconversion"
-If built with internationalization support,
-this option controls conversion of UTF-8 in message addresses
-to a-label form.
-For details see section &<<SECTi18nMTA>>&.
-
-
-
-
-.section "How the limits for the number of hosts to try are used" &&&
-         "SECTvalhosmax"
-.cindex "host" "maximum number to try"
-.cindex "limit" "hosts; maximum number tried"
-There are two options that are concerned with the number of hosts that are
-tried when an SMTP delivery takes place. They are &%hosts_max_try%& and
-&%hosts_max_try_hardlimit%&.
-
-
-The &%hosts_max_try%& option limits the number of hosts that are tried
-for a single delivery. However, despite the term &"host"& in its name, the
-option actually applies to each IP address independently. In other words, a
-multihomed host is treated as several independent hosts, just as it is for
-retrying.
-
-Many of the larger ISPs have multiple MX records which often point to
-multihomed hosts. As a result, a list of a dozen or more IP addresses may be
-created as a result of routing one of these domains.
-
-Trying every single IP address on such a long list does not seem sensible; if
-several at the top of the list fail, it is reasonable to assume there is some
-problem that is likely to affect all of them. Roughly speaking, the value of
-&%hosts_max_try%& is the maximum number that are tried before deferring the
-delivery. However, the logic cannot be quite that simple.
-
-Firstly, IP addresses that are skipped because their retry times have not
-arrived do not count, and in addition, addresses that are past their retry
-limits are also not counted, even when they are tried. This means that when
-some IP addresses are past their retry limits, more than the value of
-&%hosts_max_retry%& may be tried. The reason for this behaviour is to ensure
-that all IP addresses are considered before timing out an email address (but
-see below for an exception).
-
-Secondly, when the &%hosts_max_try%& limit is reached, Exim looks down the host
-list to see if there is a subsequent host with a different (higher valued) MX.
-If there is, that host is considered next, and the current IP address is used
-but not counted. This behaviour helps in the case of a domain with a retry rule
-that hardly ever delays any hosts, as is now explained:
-
-Consider the case of a long list of hosts with one MX value, and a few with a
-higher MX value. If &%hosts_max_try%& is small (the default is 5) only a few
-hosts at the top of the list are tried at first. With the default retry rule,
-which specifies increasing retry times, the higher MX hosts are eventually
-tried when those at the top of the list are skipped because they have not
-reached their retry times.
-
-However, it is common practice to put a fixed short retry time on domains for
-large ISPs, on the grounds that their servers are rarely down for very long.
-Unfortunately, these are exactly the domains that tend to resolve to long lists
-of hosts. The short retry time means that the lowest MX hosts are tried every
-time. The attempts may be in a different order because of random sorting, but
-without the special MX check, the higher MX hosts would never be tried until
-all the lower MX hosts had timed out (which might be several days), because
-there are always some lower MX hosts that have reached their retry times. With
-the special check, Exim considers at least one IP address from each MX value at
-every delivery attempt, even if the &%hosts_max_try%& limit has already been
-reached.
-
-The above logic means that &%hosts_max_try%& is not a hard limit, and in
-particular, Exim normally eventually tries all the IP addresses before timing
-out an email address. When &%hosts_max_try%& was implemented, this seemed a
-reasonable thing to do. Recently, however, some lunatic DNS configurations have
-been set up with hundreds of IP addresses for some domains. It can
-take a very long time indeed for an address to time out in these cases.
-
-The &%hosts_max_try_hardlimit%& option was added to help with this problem.
-Exim never tries more than this number of IP addresses; if it hits this limit
-and they are all timed out, the email address is bounced, even though not all
-possible IP addresses have been tried.
-.ecindex IIDsmttra1
-.ecindex IIDsmttra2
-
-
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "Address rewriting" "CHAPrewrite"
-.scindex IIDaddrew "rewriting" "addresses"
-There are some circumstances in which Exim automatically rewrites domains in
-addresses. The two most common are when an address is given without a domain
-(referred to as an &"unqualified address"&) or when an address contains an
-abbreviated domain that is expanded by DNS lookup.
-
-Unqualified envelope addresses are accepted only for locally submitted
-messages, or for messages that are received from hosts matching
-&%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
-appropriate. Unqualified addresses in header lines are qualified if they are in
-locally submitted messages, or messages from hosts that are permitted to send
-unqualified envelope addresses. Otherwise, unqualified addresses in header
-lines are neither qualified nor rewritten.
-
-One situation in which Exim does &'not'& automatically rewrite a domain is
-when it is the name of a CNAME record in the DNS. The older RFCs suggest that
-such a domain should be rewritten using the &"canonical"& name, and some MTAs
-do this. The new RFCs do not contain this suggestion.
-
-
-.section "Explicitly configured address rewriting" "SECID147"
-This chapter describes the rewriting rules that can be used in the
-main rewrite section of the configuration file, and also in the generic
-&%headers_rewrite%& option that can be set on any transport.
-
-Some people believe that configured address rewriting is a Mortal Sin.
-Others believe that life is not possible without it. Exim provides the
-facility; you do not have to use it.
-
-The main rewriting rules that appear in the &"rewrite"& section of the
-configuration file are applied to addresses in incoming messages, both envelope
-addresses and addresses in header lines. Each rule specifies the types of
-address to which it applies.
-
-Whether or not addresses in header lines are rewritten depends on the origin of
-the headers and the type of rewriting. Global rewriting, that is, rewriting
-rules from the rewrite section of the configuration file, is applied only to
-those headers that were received with the message. Header lines that are added
-by ACLs or by a system filter or by individual routers or transports (which
-are specific to individual recipient addresses) are not rewritten by the global
-rules.
-
-Rewriting at transport time, by means of the &%headers_rewrite%& option,
-applies all headers except those added by routers and transports. That is, as
-well as the headers that were received with the message, it also applies to
-headers that were added by an ACL or a system filter.
-
-
-In general, rewriting addresses from your own system or domain has some
-legitimacy. Rewriting other addresses should be done only with great care and
-in special circumstances. The author of Exim believes that rewriting should be
-used sparingly, and mainly for &"regularizing"& addresses in your own domains.
-Although it can sometimes be used as a routing tool, this is very strongly
-discouraged.
-
-There are two commonly encountered circumstances where rewriting is used, as
-illustrated by these examples:
-
-.ilist
-The company whose domain is &'hitch.fict.example'& has a number of hosts that
-exchange mail with each other behind a firewall, but there is only a single
-gateway to the outer world. The gateway rewrites &'*.hitch.fict.example'& as
-&'hitch.fict.example'& when sending mail off-site.
-.next
-A host rewrites the local parts of its own users so that, for example,
-&'fp42@hitch.fict.example'& becomes &'Ford.Prefect@hitch.fict.example'&.
-.endlist
-
-
-
-.section "When does rewriting happen?" "SECID148"
-.cindex "rewriting" "timing of"
-.cindex "&ACL;" "rewriting addresses in"
-Configured address rewriting can take place at several different stages of a
-message's processing.
-
-.vindex "&$sender_address$&"
-At the start of an ACL for MAIL, the sender address may have been rewritten
-by a special SMTP-time rewrite rule (see section &<<SECTrewriteS>>&), but no
-ordinary rewrite rules have yet been applied. If, however, the sender address
-is verified in the ACL, it is rewritten before verification, and remains
-rewritten thereafter. The subsequent value of &$sender_address$& is the
-rewritten address. This also applies if sender verification happens in a
-RCPT ACL. Otherwise, when the sender address is not verified, it is
-rewritten as soon as a message's header lines have been received.
-
-.vindex "&$domain$&"
-.vindex "&$local_part$&"
-Similarly, at the start of an ACL for RCPT, the current recipient's address
-may have been rewritten by a special SMTP-time rewrite rule, but no ordinary
-rewrite rules have yet been applied to it. However, the behaviour is different
-from the sender address when a recipient is verified. The address is rewritten
-for the verification, but the rewriting is not remembered at this stage. The
-value of &$local_part$& and &$domain$& after verification are always the same
-as they were before (that is, they contain the unrewritten &-- except for
-SMTP-time rewriting &-- address).
-
-As soon as a message's header lines have been received, all the envelope
-recipient addresses are permanently rewritten, and rewriting is also applied to
-the addresses in the header lines (if configured). This happens before adding
-any header lines that were specified in MAIL or RCPT ACLs, and
-.cindex "&[local_scan()]& function" "address rewriting; timing of"
-before the DATA ACL and &[local_scan()]& functions are run.
-
-When an address is being routed, either for delivery or for verification,
-rewriting is applied immediately to child addresses that are generated by
-redirection, unless &%no_rewrite%& is set on the router.
-
-.cindex "envelope from"
-.cindex "envelope sender" "rewriting at transport time"
-.cindex "rewriting" "at transport time"
-.cindex "header lines" "rewriting at transport time"
-At transport time, additional rewriting of addresses in header lines can be
-specified by setting the generic &%headers_rewrite%& option on a transport.
-This option contains rules that are identical in form to those in the rewrite
-section of the configuration file. They are applied to the original message
-header lines and any that were added by ACLs or a system filter. They are not
-applied to header lines that are added by routers or the transport.
-
-The outgoing envelope sender can be rewritten by means of the &%return_path%&
-transport option. However, it is not possible to rewrite envelope recipients at
-transport time.
-
-
-
-
-.section "Testing the rewriting rules that apply on input" "SECID149"
-.cindex "rewriting" "testing"
-.cindex "testing" "rewriting"
-Exim's input rewriting configuration appears in a part of the runtime
-configuration file headed by &"begin rewrite"&. It can be tested by the
-&%-brw%& command line option. This takes an address (which can be a full RFC
-2822 address) as its argument. The output is a list of how the address would be
-transformed by the rewriting rules for each of the different places it might
-appear in an incoming message, that is, for each different header and for the
-envelope sender and recipient fields. For example,
-.code
-exim -brw ph10@exim.workshop.example
-.endd
-might produce the output
-.code
-sender: Philip.Hazel@exim.workshop.example
-from: Philip.Hazel@exim.workshop.example
-to: ph10@exim.workshop.example
-cc: ph10@exim.workshop.example
-bcc: ph10@exim.workshop.example
-reply-to: Philip.Hazel@exim.workshop.example
-env-from: Philip.Hazel@exim.workshop.example
-env-to: ph10@exim.workshop.example
-.endd
-which shows that rewriting has been set up for that address when used in any of
-the source fields, but not when it appears as a recipient address. At the
-present time, there is no equivalent way of testing rewriting rules that are
-set for a particular transport.
-
-
-.section "Rewriting rules" "SECID150"
-.cindex "rewriting" "rules"
-The rewrite section of the configuration file consists of lines of rewriting
-rules in the form
-.display
-<&'source pattern'&>  <&'replacement'&>  <&'flags'&>
-.endd
-Rewriting rules that are specified for the &%headers_rewrite%& generic
-transport option are given as a colon-separated list. Each item in the list
-takes the same form as a line in the main rewriting configuration (except that
-any colons must be doubled, of course).
-
-The formats of source patterns and replacement strings are described below.
-Each is terminated by white space, unless enclosed in double quotes, in which
-case normal quoting conventions apply inside the quotes. The flags are single
-characters which may appear in any order. Spaces and tabs between them are
-ignored.
-
-For each address that could potentially be rewritten, the rules are scanned in
-order, and replacements for the address from earlier rules can themselves be
-replaced by later rules (but see the &"q"& and &"R"& flags).
-
-The order in which addresses are rewritten is undefined, may change between
-releases, and must not be relied on, with one exception: when a message is
-received, the envelope sender is always rewritten first, before any header
-lines are rewritten. For example, the replacement string for a rewrite of an
-address in &'To:'& must not assume that the message's address in &'From:'& has
-(or has not) already been rewritten. However, a rewrite of &'From:'& may assume
-that the envelope sender has already been rewritten.
-
-.vindex "&$domain$&"
-.vindex "&$local_part$&"
-The variables &$local_part$& and &$domain$& can be used in the replacement
-string to refer to the address that is being rewritten. Note that lookup-driven
-rewriting can be done by a rule of the form
-.code
-*@*   ${lookup ...
-.endd
-where the lookup key uses &$1$& and &$2$& or &$local_part$& and &$domain$& to
-refer to the address that is being rewritten.
-
-
-.section "Rewriting patterns" "SECID151"
-.cindex "rewriting" "patterns"
-.cindex "address list" "in a rewriting pattern"
-The source pattern in a rewriting rule is any item which may appear in an
-address list (see section &<<SECTaddresslist>>&). It is in fact processed as a
-single-item address list, which means that it is expanded before being tested
-against the address. As always, if you use a regular expression as a pattern,
-you must take care to escape dollar and backslash characters, or use the &`\N`&
-facility to suppress string expansion within the regular expression.
-
-Domains in patterns should be given in lower case. Local parts in patterns are
-case-sensitive. If you want to do case-insensitive matching of local parts, you
-can use a regular expression that starts with &`^(?i)`&.
-
-.cindex "numerical variables (&$1$& &$2$& etc)" "in rewriting rules"
-After matching, the numerical variables &$1$&, &$2$&, etc. may be set,
-depending on the type of match which occurred. These can be used in the
-replacement string to insert portions of the incoming address. &$0$& always
-refers to the complete incoming address. When a regular expression is used, the
-numerical variables are set from its capturing subexpressions. For other types
-of pattern they are set as follows:
-
-.ilist
-If a local part or domain starts with an asterisk, the numerical variables
-refer to the character strings matched by asterisks, with &$1$& associated with
-the first asterisk, and &$2$& with the second, if present. For example, if the
-pattern
-.code
-*queen@*.fict.example
-.endd
-is matched against the address &'hearts-queen@wonderland.fict.example'& then
-.code
-$0 = hearts-queen@wonderland.fict.example
-$1 = hearts-
-$2 = wonderland
-.endd
-Note that if the local part does not start with an asterisk, but the domain
-does, it is &$1$& that contains the wild part of the domain.
-
-.next
-If the domain part of the pattern is a partial lookup, the wild and fixed parts
-of the domain are placed in the next available numerical variables. Suppose,
-for example, that the address &'foo@bar.baz.example'& is processed by a
-rewriting rule of the form
-.display
-&`*@partial-dbm;/some/dbm/file`&    <&'replacement string'&>
-.endd
-and the key in the file that matches the domain is &`*.baz.example`&. Then
-.code
-$1 = foo
-$2 = bar
-$3 = baz.example
-.endd
-If the address &'foo@baz.example'& is looked up, this matches the same
-wildcard file entry, and in this case &$2$& is set to the empty string, but
-&$3$& is still set to &'baz.example'&. If a non-wild key is matched in a
-partial lookup, &$2$& is again set to the empty string and &$3$& is set to the
-whole domain. For non-partial domain lookups, no numerical variables are set.
-.endlist
-
-
-.section "Rewriting replacements" "SECID152"
-.cindex "rewriting" "replacements"
-If the replacement string for a rule is a single asterisk, addresses that
-match the pattern and the flags are &'not'& rewritten, and no subsequent
-rewriting rules are scanned. For example,
-.code
-hatta@lookingglass.fict.example  *  f
-.endd
-specifies that &'hatta@lookingglass.fict.example'& is never to be rewritten in
-&'From:'& headers.
-
-.vindex "&$domain$&"
-.vindex "&$local_part$&"
-If the replacement string is not a single asterisk, it is expanded, and must
-yield a fully qualified address. Within the expansion, the variables
-&$local_part$& and &$domain$& refer to the address that is being rewritten.
-Any letters they contain retain their original case &-- they are not lower
-cased. The numerical variables are set up according to the type of pattern that
-matched the address, as described above. If the expansion is forced to fail by
-the presence of &"fail"& in a conditional or lookup item, rewriting by the
-current rule is abandoned, but subsequent rules may take effect. Any other
-expansion failure causes the entire rewriting operation to be abandoned, and an
-entry written to the panic log.
-
-
-
-.section "Rewriting flags" "SECID153"
-There are three different kinds of flag that may appear on rewriting rules:
-
-.ilist
-Flags that specify which headers and envelope addresses to rewrite: E, F, T, b,
-c, f, h, r, s, t.
-.next
-A flag that specifies rewriting at SMTP time: S.
-.next
-Flags that control the rewriting process: Q, q, R, w.
-.endlist
-
-For rules that are part of the &%headers_rewrite%& generic transport option,
-E, F, T, and S are not permitted.
-
-
-
-.section "Flags specifying which headers and envelope addresses to rewrite" &&&
-         "SECID154"
-.cindex "rewriting" "flags"
-If none of the following flag letters, nor the &"S"& flag (see section
-&<<SECTrewriteS>>&) are present, a main rewriting rule applies to all headers
-and to both the sender and recipient fields of the envelope, whereas a
-transport-time rewriting rule just applies to all headers. Otherwise, the
-rewriting rule is skipped unless the relevant addresses are being processed.
-.display
-&`E`&       rewrite all envelope fields
-&`F`&       rewrite the envelope From field
-&`T`&       rewrite the envelope To field
-&`b`&       rewrite the &'Bcc:'& header
-&`c`&       rewrite the &'Cc:'& header
-&`f`&       rewrite the &'From:'& header
-&`h`&       rewrite all headers
-&`r`&       rewrite the &'Reply-To:'& header
-&`s`&       rewrite the &'Sender:'& header
-&`t`&       rewrite the &'To:'& header
-.endd
-"All headers" means all of the headers listed above that can be selected
-individually, plus their &'Resent-'& versions. It does not include
-other headers such as &'Subject:'& etc.
-
-You should be particularly careful about rewriting &'Sender:'& headers, and
-restrict this to special known cases in your own domains.
-
-
-.section "The SMTP-time rewriting flag" "SECTrewriteS"
-.cindex "SMTP" "rewriting malformed addresses"
-.cindex "RCPT" "rewriting argument of"
-.cindex "MAIL" "rewriting argument of"
-The rewrite flag &"S"& specifies a rewrite of incoming envelope addresses at
-SMTP time, as soon as an address is received in a MAIL or RCPT command, and
-before any other processing; even before syntax checking. The pattern is
-required to be a regular expression, and it is matched against the whole of the
-data for the command, including any surrounding angle brackets.
-
-.vindex "&$domain$&"
-.vindex "&$local_part$&"
-This form of rewrite rule allows for the handling of addresses that are not
-compliant with RFCs 2821 and 2822 (for example, &"bang paths"& in batched SMTP
-input). Because the input is not required to be a syntactically valid address,
-the variables &$local_part$& and &$domain$& are not available during the
-expansion of the replacement string. The result of rewriting replaces the
-original address in the MAIL or RCPT command.
-
-
-.section "Flags controlling the rewriting process" "SECID155"
-There are four flags which control the way the rewriting process works. These
-take effect only when a rule is invoked, that is, when the address is of the
-correct type (matches the flags) and matches the pattern:
-
-.ilist
-If the &"Q"& flag is set on a rule, the rewritten address is permitted to be an
-unqualified local part. It is qualified with &%qualify_recipient%&. In the
-absence of &"Q"& the rewritten address must always include a domain.
-.next
-If the &"q"& flag is set on a rule, no further rewriting rules are considered,
-even if no rewriting actually takes place because of a &"fail"& in the
-expansion. The &"q"& flag is not effective if the address is of the wrong type
-(does not match the flags) or does not match the pattern.
-.next
-The &"R"& flag causes a successful rewriting rule to be re-applied to the new
-address, up to ten times. It can be combined with the &"q"& flag, to stop
-rewriting once it fails to match (after at least one successful rewrite).
-.next
-.cindex "rewriting" "whole addresses"
-When an address in a header is rewritten, the rewriting normally applies only
-to the working part of the address, with any comments and RFC 2822 &"phrase"&
-left unchanged. For example, rewriting might change
-.code
-From: Ford Prefect <fp42@restaurant.hitch.fict.example>
-.endd
-into
-.code
-From: Ford Prefect <prefectf@hitch.fict.example>
-.endd
-.cindex "RFC 2047"
-Sometimes there is a need to replace the whole address item, and this can be
-done by adding the flag letter &"w"& to a rule. If this is set on a rule that
-causes an address in a header line to be rewritten, the entire address is
-replaced, not just the working part. The replacement must be a complete RFC
-2822 address, including the angle brackets if necessary. If text outside angle
-brackets contains a character whose value is greater than 126 or less than 32
-(except for tab), the text is encoded according to RFC 2047. The character set
-is taken from &%headers_charset%&, which gets its default at build time.
-
-When the &"w"& flag is set on a rule that causes an envelope address to be
-rewritten, all but the working part of the replacement address is discarded.
-.endlist
-
-
-.section "Rewriting examples" "SECID156"
-Here is an example of the two common rewriting paradigms:
-.code
-*@*.hitch.fict.example  $1@hitch.fict.example
-*@hitch.fict.example    ${lookup{$1}dbm{/etc/realnames}\
-                     {$value}fail}@hitch.fict.example bctfrF
-.endd
-Note the use of &"fail"& in the lookup expansion in the second rule, forcing
-the string expansion to fail if the lookup does not succeed. In this context it
-has the effect of leaving the original address unchanged, but Exim goes on to
-consider subsequent rewriting rules, if any, because the &"q"& flag is not
-present in that rule. An alternative to &"fail"& would be to supply &$1$&
-explicitly, which would cause the rewritten address to be the same as before,
-at the cost of a small bit of processing. Not supplying either of these is an
-error, since the rewritten address would then contain no local part.
-
-The first example above replaces the domain with a superior, more general
-domain. This may not be desirable for certain local parts. If the rule
-.code
-root@*.hitch.fict.example  *
-.endd
-were inserted before the first rule, rewriting would be suppressed for the
-local part &'root'& at any domain ending in &'hitch.fict.example'&.
-
-Rewriting can be made conditional on a number of tests, by making use of
-&${if$& in the expansion item. For example, to apply a rewriting rule only to
-messages that originate outside the local host:
-.code
-*@*.hitch.fict.example  "${if !eq {$sender_host_address}{}\
-                         {$1@hitch.fict.example}fail}"
-.endd
-The replacement string is quoted in this example because it contains white
-space.
-
-.cindex "rewriting" "bang paths"
-.cindex "bang paths" "rewriting"
-Exim does not handle addresses in the form of &"bang paths"&. If it sees such
-an address it treats it as an unqualified local part which it qualifies with
-the local qualification domain (if the source of the message is local or if the
-remote host is permitted to send unqualified addresses). Rewriting can
-sometimes be used to handle simple bang paths with a fixed number of
-components. For example, the rule
-.code
-\N^([^!]+)!(.*)@your.domain.example$\N   $2@$1
-.endd
-rewrites a two-component bang path &'host.name!user'& as the domain address
-&'user@host.name'&. However, there is a security implication in using this as
-a global rewriting rule for envelope addresses. It can provide a backdoor
-method for using your system as a relay, because the incoming addresses appear
-to be local. If the bang path addresses are received via SMTP, it is safer to
-use the &"S"& flag to rewrite them as they are received, so that relay checking
-can be done on the rewritten addresses.
-.ecindex IIDaddrew
-
-
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "Retry configuration" "CHAPretry"
-.scindex IIDretconf1 "retry" "configuration, description of"
-.scindex IIDregconf2 "configuration file" "retry section"
-The &"retry"& section of the runtime configuration file contains a list of
-retry rules that control how often Exim tries to deliver messages that cannot
-be delivered at the first attempt. If there are no retry rules (the section is
-empty or not present), there are no retries. In this situation, temporary
-errors are treated as permanent. The default configuration contains a single,
-general-purpose retry rule (see section &<<SECID57>>&). The &%-brt%& command
-line option can be used to test which retry rule will be used for a given
-address, domain and error.
-
-The most common cause of retries is temporary failure to deliver to a remote
-host because the host is down, or inaccessible because of a network problem.
-Exim's retry processing in this case is applied on a per-host (strictly, per IP
-address) basis, not on a per-message basis. Thus, if one message has recently
-been delayed, delivery of a new message to the same host is not immediately
-tried, but waits for the host's retry time to arrive. If the &%retry_defer%&
-log selector is set, the message
-.cindex "retry" "time not reached"
-&"retry time not reached"& is written to the main log whenever a delivery is
-skipped for this reason. Section &<<SECToutSMTPerr>>& contains more details of
-the handling of errors during remote deliveries.
-
-Retry processing applies to routing as well as to delivering, except as covered
-in the next paragraph. The retry rules do not distinguish between these
-actions. It is not possible, for example, to specify different behaviour for
-failures to route the domain &'snark.fict.example'& and failures to deliver to
-the host &'snark.fict.example'&. I didn't think anyone would ever need this
-added complication, so did not implement it. However, although they share the
-same retry rule, the actual retry times for routing and transporting a given
-domain are maintained independently.
-
-When a delivery is not part of a queue run (typically an immediate delivery on
-receipt of a message), the routers are always run, and local deliveries are
-always attempted, even if retry times are set for them. This makes for better
-behaviour if one particular message is causing problems (for example, causing
-quota overflow, or provoking an error in a filter file). If such a delivery
-suffers a temporary failure, the retry data is updated as normal, and
-subsequent delivery attempts from queue runs occur only when the retry time for
-the local address is reached.
-
-.section "Changing retry rules" "SECID157"
-If you change the retry rules in your configuration, you should consider
-whether or not to delete the retry data that is stored in Exim's spool area in
-files with names like &_db/retry_&. Deleting any of Exim's hints files is
-always safe; that is why they are called &"hints"&.
-
-The hints retry data contains suggested retry times based on the previous
-rules. In the case of a long-running problem with a remote host, it might
-record the fact that the host has timed out. If your new rules increase the
-timeout time for such a host, you should definitely remove the old retry data
-and let Exim recreate it, based on the new rules. Otherwise Exim might bounce
-messages that it should now be retaining.
-
-
-
-.section "Format of retry rules" "SECID158"
-.cindex "retry" "rules"
-Each retry rule occupies one line and consists of three or four parts,
-separated by white space: a pattern, an error name, an optional list of sender
-addresses, and a list of retry parameters. The pattern and sender lists must be
-enclosed in double quotes if they contain white space. The rules are searched
-in order until one is found where the pattern, error name, and sender list (if
-present) match the failing host or address, the error that occurred, and the
-message's sender, respectively.
-
-
-The pattern is any single item that may appear in an address list (see section
-&<<SECTaddresslist>>&). It is in fact processed as a one-item address list,
-which means that it is expanded before being tested against the address that
-has been delayed. A negated address list item is permitted. Address
-list processing treats a plain domain name as if it were preceded by &"*@"&,
-which makes it possible for many retry rules to start with just a domain. For
-example,
-.code
-lookingglass.fict.example        *  F,24h,30m;
-.endd
-provides a rule for any address in the &'lookingglass.fict.example'& domain,
-whereas
-.code
-alice@lookingglass.fict.example  *  F,24h,30m;
-.endd
-applies only to temporary failures involving the local part &%alice%&.
-In practice, almost all rules start with a domain name pattern without a local
-part.
-
-.cindex "regular expressions" "in retry rules"
-&*Warning*&: If you use a regular expression in a retry rule pattern, it
-must match a complete address, not just a domain, because that is how regular
-expressions work in address lists.
-.display
-&`^\Nxyz\d+\.abc\.example$\N        *  G,1h,10m,2`&     &%Wrong%&
-&`^\N[^@]+@xyz\d+\.abc\.example$\N  *  G,1h,10m,2`&     &%Right%&
-.endd
-
-
-.section "Choosing which retry rule to use for address errors" "SECID159"
-When Exim is looking for a retry rule after a routing attempt has failed (for
-example, after a DNS timeout), each line in the retry configuration is tested
-against the complete address only if &%retry_use_local_part%& is set for the
-router. Otherwise, only the domain is used, except when matching against a
-regular expression, when the local part of the address is replaced with &"*"&.
-A domain on its own can match a domain pattern, or a pattern that starts with
-&"*@"&. By default, &%retry_use_local_part%& is true for routers where
-&%check_local_user%& is true, and false for other routers.
-
-Similarly, when Exim is looking for a retry rule after a local delivery has
-failed (for example, after a mailbox full error), each line in the retry
-configuration is tested against the complete address only if
-&%retry_use_local_part%& is set for the transport (it defaults true for all
-local transports).
-
-.cindex "4&'xx'& responses" "retry rules for"
-However, when Exim is looking for a retry rule after a remote delivery attempt
-suffers an address error (a 4&'xx'& SMTP response for a recipient address), the
-whole address is always used as the key when searching the retry rules. The
-rule that is found is used to create a retry time for the combination of the
-failing address and the message's sender. It is the combination of sender and
-recipient that is delayed in subsequent queue runs until its retry time is
-reached. You can delay the recipient without regard to the sender by setting
-&%address_retry_include_sender%& false in the &(smtp)& transport but this can
-lead to problems with servers that regularly issue 4&'xx'& responses to RCPT
-commands.
-
-
-
-.section "Choosing which retry rule to use for host and message errors" &&&
-         "SECID160"
-For a temporary error that is not related to an individual address (for
-example, a connection timeout), each line in the retry configuration is checked
-twice. First, the name of the remote host is used as a domain name (preceded by
-&"*@"& when matching a regular expression). If this does not match the line,
-the domain from the email address is tried in a similar fashion. For example,
-suppose the MX records for &'a.b.c.example'& are
-.code
-a.b.c.example  MX  5  x.y.z.example
-               MX  6  p.q.r.example
-               MX  7  m.n.o.example
-.endd
-and the retry rules are
-.code
-p.q.r.example    *      F,24h,30m;
-a.b.c.example    *      F,4d,45m;
-.endd
-and a delivery to the host &'x.y.z.example'& suffers a connection failure. The
-first rule matches neither the host nor the domain, so Exim looks at the second
-rule. This does not match the host, but it does match the domain, so it is used
-to calculate the retry time for the host &'x.y.z.example'&. Meanwhile, Exim
-tries to deliver to &'p.q.r.example'&. If this also suffers a host error, the
-first retry rule is used, because it matches the host.
-
-In other words, temporary failures to deliver to host &'p.q.r.example'& use the
-first rule to determine retry times, but for all the other hosts for the domain
-&'a.b.c.example'&, the second rule is used. The second rule is also used if
-routing to &'a.b.c.example'& suffers a temporary failure.
-
-&*Note*&: The host name is used when matching the patterns, not its IP address.
-However, if a message is routed directly to an IP address without the use of a
-host name, for example, if a &(manualroute)& router contains a setting such as:
-.code
-route_list = *.a.example  192.168.34.23
-.endd
-then the &"host name"& that is used when searching for a retry rule is the
-textual form of the IP address.
-
-.section "Retry rules for specific errors" "SECID161"
-.cindex "retry" "specific errors; specifying"
-The second field in a retry rule is the name of a particular error, or an
-asterisk, which matches any error. The errors that can be tested for are:
-
-.vlist
-.vitem &%auth_failed%&
-Authentication failed when trying to send to a host in the
-&%hosts_require_auth%& list in an &(smtp)& transport.
-
-.vitem &%data_4xx%&
-A 4&'xx'& error was received for an outgoing DATA command, either immediately
-after the command, or after sending the message's data.
-
-.vitem &%mail_4xx%&
-A 4&'xx'& error was received for an outgoing MAIL command.
-
-.vitem &%rcpt_4xx%&
-A 4&'xx'& error was received for an outgoing RCPT command.
-.endlist
-
-For the three 4&'xx'& errors, either the first or both of the x's can be given
-as specific digits, for example: &`mail_45x`& or &`rcpt_436`&. For example, to
-recognize 452 errors given to RCPT commands for addresses in a certain domain,
-and have retries every ten minutes with a one-hour timeout, you could set up a
-retry rule of this form:
-.code
-the.domain.name  rcpt_452   F,1h,10m
-.endd
-These errors apply to both outgoing SMTP (the &(smtp)& transport) and outgoing
-LMTP (either the &(lmtp)& transport, or the &(smtp)& transport in LMTP mode).
-
-.vlist
-.vitem &%lost_connection%&
-A server unexpectedly closed the SMTP connection. There may, of course,
-legitimate reasons for this (host died, network died), but if it repeats a lot
-for the same host, it indicates something odd.
-
-.vitem &%lookup%&
-A DNS lookup for a host failed.
-Note that a &%dnslookup%& router will need to have matched
-its &%fail_defer_domains%& option for this retry type to be usable.
-Also note that a &%manualroute%& router will probably need
-its &%host_find_failed%& option set to &%defer%&.
-
-.vitem &%refused_MX%&
-A connection to a host obtained from an MX record was refused.
-
-.vitem &%refused_A%&
-A connection to a host not obtained from an MX record was refused.
-
-.vitem &%refused%&
-A connection was refused.
-
-.vitem &%timeout_connect_MX%&
-A connection attempt to a host obtained from an MX record timed out.
-
-.vitem &%timeout_connect_A%&
-A connection attempt to a host not obtained from an MX record timed out.
-
-.vitem &%timeout_connect%&
-A connection attempt timed out.
-
-.vitem &%timeout_MX%&
-There was a timeout while connecting or during an SMTP session with a host
-obtained from an MX record.
-
-.vitem &%timeout_A%&
-There was a timeout while connecting or during an SMTP session with a host not
-obtained from an MX record.
-
-.vitem &%timeout%&
-There was a timeout while connecting or during an SMTP session.
-
-.vitem &%tls_required%&
-The server was required to use TLS (it matched &%hosts_require_tls%& in the
-&(smtp)& transport), but either did not offer TLS, or it responded with 4&'xx'&
-to STARTTLS, or there was a problem setting up the TLS connection.
-
-.vitem &%quota%&
-A mailbox quota was exceeded in a local delivery by the &(appendfile)&
-transport.
-
-.vitem &%quota_%&<&'time'&>
-.cindex "quota" "error testing in retry rule"
-.cindex "retry" "quota error testing"
-A mailbox quota was exceeded in a local delivery by the &(appendfile)&
-transport, and the mailbox has not been accessed for <&'time'&>. For example,
-&'quota_4d'& applies to a quota error when the mailbox has not been accessed
-for four days.
-.endlist
-
-.cindex "mailbox" "time of last read"
-The idea of &%quota_%&<&'time'&> is to make it possible to have shorter
-timeouts when the mailbox is full and is not being read by its owner. Ideally,
-it should be based on the last time that the user accessed the mailbox.
-However, it is not always possible to determine this. Exim uses the following
-heuristic rules:
-
-.ilist
-If the mailbox is a single file, the time of last access (the &"atime"&) is
-used. As no new messages are being delivered (because the mailbox is over
-quota), Exim does not access the file, so this is the time of last user access.
-.next
-.cindex "maildir format" "time of last read"
-For a maildir delivery, the time of last modification of the &_new_&
-subdirectory is used. As the mailbox is over quota, no new files are created in
-the &_new_& subdirectory, because no new messages are being delivered. Any
-change to the &_new_& subdirectory is therefore assumed to be the result of an
-MUA moving a new message to the &_cur_& directory when it is first read. The
-time that is used is therefore the last time that the user read a new message.
-.next
-For other kinds of multi-file mailbox, the time of last access cannot be
-obtained, so a retry rule that uses this type of error field is never matched.
-.endlist
-
-The quota errors apply both to system-enforced quotas and to Exim's own quota
-mechanism in the &(appendfile)& transport. The &'quota'& error also applies
-when a local delivery is deferred because a partition is full (the ENOSPC
-error).
-
-
-
-.section "Retry rules for specified senders" "SECID162"
-.cindex "retry" "rules; sender-specific"
-You can specify retry rules that apply only when the failing message has a
-specific sender. In particular, this can be used to define retry rules that
-apply only to bounce messages. The third item in a retry rule can be of this
-form:
-.display
-&`senders=`&<&'address list'&>
-.endd
-The retry timings themselves are then the fourth item. For example:
-.code
-*   rcpt_4xx   senders=:   F,1h,30m
-.endd
-matches recipient 4&'xx'& errors for bounce messages sent to any address at any
-host. If the address list contains white space, it must be enclosed in quotes.
-For example:
-.code
-a.domain  rcpt_452  senders="xb.dom : yc.dom"  G,8h,10m,1.5
-.endd
-&*Warning*&: This facility can be unhelpful if it is used for host errors
-(which do not depend on the recipient). The reason is that the sender is used
-only to match the retry rule. Once the rule has been found for a host error,
-its contents are used to set a retry time for the host, and this will apply to
-all messages, not just those with specific senders.
-
-When testing retry rules using &%-brt%&, you can supply a sender using the
-&%-f%& command line option, like this:
-.code
-exim -f "" -brt user@dom.ain
-.endd
-If you do not set &%-f%& with &%-brt%&, a retry rule that contains a senders
-list is never matched.
-
-
-
-
-
-.section "Retry parameters" "SECID163"
-.cindex "retry" "parameters in rules"
-The third (or fourth, if a senders list is present) field in a retry rule is a
-sequence of retry parameter sets, separated by semicolons. Each set consists of
-.display
-<&'letter'&>,<&'cutoff time'&>,<&'arguments'&>
-.endd
-The letter identifies the algorithm for computing a new retry time; the cutoff
-time is the time beyond which this algorithm no longer applies, and the
-arguments vary the algorithm's action. The cutoff time is measured from the
-time that the first failure for the domain (combined with the local part if
-relevant) was detected, not from the time the message was received.
-
-.cindex "retry" "algorithms"
-.cindex "retry" "fixed intervals"
-.cindex "retry" "increasing intervals"
-.cindex "retry" "random intervals"
-The available algorithms are:
-
-.ilist
-&'F'&: retry at fixed intervals. There is a single time parameter specifying
-the interval.
-.next
-&'G'&: retry at geometrically increasing intervals. The first argument
-specifies a starting value for the interval, and the second a multiplier, which
-is used to increase the size of the interval at each retry.
-.next
-&'H'&: retry at randomized intervals. The arguments are as for &'G'&. For each
-retry, the previous interval is multiplied by the factor in order to get a
-maximum for the next interval. The minimum interval is the first argument of
-the parameter, and an actual interval is chosen randomly between them. Such a
-rule has been found to be helpful in cluster configurations when all the
-members of the cluster restart at once, and may therefore synchronize their
-queue processing times.
-.endlist
-
-When computing the next retry time, the algorithm definitions are scanned in
-order until one whose cutoff time has not yet passed is reached. This is then
-used to compute a new retry time that is later than the current time. In the
-case of fixed interval retries, this simply means adding the interval to the
-current time. For geometrically increasing intervals, retry intervals are
-computed from the rule's parameters until one that is greater than the previous
-interval is found. The main configuration variable
-.cindex "limit" "retry interval"
-.cindex "retry" "interval, maximum"
-.oindex "&%retry_interval_max%&"
-&%retry_interval_max%& limits the maximum interval between retries. It
-cannot be set greater than &`24h`&, which is its default value.
-
-A single remote domain may have a number of hosts associated with it, and each
-host may have more than one IP address. Retry algorithms are selected on the
-basis of the domain name, but are applied to each IP address independently. If,
-for example, a host has two IP addresses and one is unusable, Exim will
-generate retry times for it and will not try to use it until its next retry
-time comes. Thus the good IP address is likely to be tried first most of the
-time.
-
-.cindex "hints database" "use for retrying"
-Retry times are hints rather than promises. Exim does not make any attempt to
-run deliveries exactly at the computed times. Instead, a queue runner process
-starts delivery processes for delayed messages periodically, and these attempt
-new deliveries only for those addresses that have passed their next retry time.
-If a new message arrives for a deferred address, an immediate delivery attempt
-occurs only if the address has passed its retry time. In the absence of new
-messages, the minimum time between retries is the interval between queue runner
-processes. There is not much point in setting retry times of five minutes if
-your queue runners happen only once an hour, unless there are a significant
-number of incoming messages (which might be the case on a system that is
-sending everything to a smart host, for example).
-
-The data in the retry hints database can be inspected by using the
-&'exim_dumpdb'& or &'exim_fixdb'& utility programs (see chapter
-&<<CHAPutils>>&). The latter utility can also be used to change the data. The
-&'exinext'& utility script can be used to find out what the next retry times
-are for the hosts associated with a particular mail domain, and also for local
-deliveries that have been deferred.
-
-
-.section "Retry rule examples" "SECID164"
-Here are some example retry rules:
-.code
-alice@wonderland.fict.example quota_5d  F,7d,3h
-wonderland.fict.example       quota_5d
-wonderland.fict.example       *         F,1h,15m; G,2d,1h,2;
-lookingglass.fict.example     *         F,24h,30m;
-*                 refused_A   F,2h,20m;
-*                 *           F,2h,15m; G,16h,1h,1.5; F,5d,8h
-.endd
-The first rule sets up special handling for mail to
-&'alice@wonderland.fict.example'& when there is an over-quota error and the
-mailbox has not been read for at least 5 days. Retries continue every three
-hours for 7 days. The second rule handles over-quota errors for all other local
-parts at &'wonderland.fict.example'&; the absence of a local part has the same
-effect as supplying &"*@"&. As no retry algorithms are supplied, messages that
-fail are bounced immediately if the mailbox has not been read for at least 5
-days.
-
-The third rule handles all other errors at &'wonderland.fict.example'&; retries
-happen every 15 minutes for an hour, then with geometrically increasing
-intervals until two days have passed since a delivery first failed. After the
-first hour there is a delay of one hour, then two hours, then four hours, and
-so on (this is a rather extreme example).
-
-The fourth rule controls retries for the domain &'lookingglass.fict.example'&.
-They happen every 30 minutes for 24 hours only. The remaining two rules handle
-all other domains, with special action for connection refusal from hosts that
-were not obtained from an MX record.
-
-The final rule in a retry configuration should always have asterisks in the
-first two fields so as to provide a general catch-all for any addresses that do
-not have their own special handling. This example tries every 15 minutes for 2
-hours, then with intervals starting at one hour and increasing by a factor of
-1.5 up to 16 hours, then every 8 hours up to 5 days.
-
-
-
-.section "Timeout of retry data" "SECID165"
-.cindex "timeout" "of retry data"
-.oindex "&%retry_data_expire%&"
-.cindex "hints database" "data expiry"
-.cindex "retry" "timeout of data"
-Exim timestamps the data that it writes to its retry hints database. When it
-consults the data during a delivery it ignores any that is older than the value
-set in &%retry_data_expire%& (default 7 days). If, for example, a host hasn't
-been tried for 7 days, Exim will try to deliver to it immediately a message
-arrives, and if that fails, it will calculate a retry time as if it were
-failing for the first time.
-
-This improves the behaviour for messages routed to rarely-used hosts such as MX
-backups. If such a host was down at one time, and happens to be down again when
-Exim tries a month later, using the old retry data would imply that it had been
-down all the time, which is not a justified assumption.
-
-If a host really is permanently dead, this behaviour causes a burst of retries
-every now and again, but only if messages routed to it are rare. If there is a
-message at least once every 7 days the retry data never expires.
-
-
-
-
-.section "Long-term failures" "SECID166"
-.cindex "delivery failure, long-term"
-.cindex "retry" "after long-term failure"
-Special processing happens when an email address has been failing for so long
-that the cutoff time for the last algorithm is reached. For example, using the
-default retry rule:
-.code
-* * F,2h,15m; G,16h,1h,1.5; F,4d,6h
-.endd
-the cutoff time is four days. Reaching the retry cutoff is independent of how
-long any specific message has been failing; it is the length of continuous
-failure for the recipient address that counts.
-
-When the cutoff time is reached for a local delivery, or for all the IP
-addresses associated with a remote delivery, a subsequent delivery failure
-causes Exim to give up on the address, and a bounce message is generated.
-In order to cater for new messages that use the failing address, a next retry
-time is still computed from the final algorithm, and is used as follows:
-
-For local deliveries, one delivery attempt is always made for any subsequent
-messages. If this delivery fails, the address fails immediately. The
-post-cutoff retry time is not used.
-
-.cindex "final cutoff" "retries, controlling"
-.cindex retry "final cutoff"
-If the delivery is remote, there are two possibilities, controlled by the
-.oindex "&%delay_after_cutoff%&"
-&%delay_after_cutoff%& option of the &(smtp)& transport. The option is true by
-default. Until the post-cutoff retry time for one of the IP addresses,
-as set by the &%retry_data_expire%& option, is
-reached, the failing email address is bounced immediately, without a delivery
-attempt taking place. After that time, one new delivery attempt is made to
-those IP addresses that are past their retry times, and if that still fails,
-the address is bounced and new retry times are computed.
-
-In other words, when all the hosts for a given email address have been failing
-for a long time, Exim bounces rather then defers until one of the hosts' retry
-times is reached. Then it tries once, and bounces if that attempt fails. This
-behaviour ensures that few resources are wasted in repeatedly trying to deliver
-to a broken destination, but if the host does recover, Exim will eventually
-notice.
-
-If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
-addresses are past their final cutoff time, Exim tries to deliver to those IP
-addresses that have not been tried since the message arrived. If there are
-no suitable IP addresses, or if they all fail, the address is bounced. In other
-words, it does not delay when a new message arrives, but tries the expired
-addresses immediately, unless they have been tried since the message arrived.
-If there is a continuous stream of messages for the failing domains, setting
-&%delay_after_cutoff%& false means that there will be many more attempts to
-deliver to permanently failing IP addresses than when &%delay_after_cutoff%& is
-true.
-
-.section "Deliveries that work intermittently" "SECID167"
-.cindex "retry" "intermittently working deliveries"
-Some additional logic is needed to cope with cases where a host is
-intermittently available, or when a message has some attribute that prevents
-its delivery when others to the same address get through. In this situation,
-because some messages are successfully delivered, the &"retry clock"& for the
-host or address keeps getting reset by the successful deliveries, and so
-failing messages remain in the queue for ever because the cutoff time is never
-reached.
-
-Two exceptional actions are applied to prevent this happening. The first
-applies to errors that are related to a message rather than a remote host.
-Section &<<SECToutSMTPerr>>& has a discussion of the different kinds of error;
-examples of message-related errors are 4&'xx'& responses to MAIL or DATA
-commands, and quota failures. For this type of error, if a message's arrival
-time is earlier than the &"first failed"& time for the error, the earlier time
-is used when scanning the retry rules to decide when to try next and when to
-time out the address.
-
-The exceptional second action applies in all cases. If a message has been on
-the queue for longer than the cutoff time of any applicable retry rule for a
-given address, a delivery is attempted for that address, even if it is not yet
-time, and if this delivery fails, the address is timed out. A new retry time is
-not computed in this case, so that other messages for the same address are
-considered immediately.
-.ecindex IIDretconf1
-.ecindex IIDregconf2
-
-
-
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "SMTP authentication" "CHAPSMTPAUTH"
-.scindex IIDauthconf1 "SMTP" "authentication configuration"
-.scindex IIDauthconf2 "authentication"
-The &"authenticators"& section of Exim's runtime configuration is concerned
-with SMTP authentication. This facility is an extension to the SMTP protocol,
-described in RFC 2554, which allows a client SMTP host to authenticate itself
-to a server. This is a common way for a server to recognize clients that are
-permitted to use it as a relay. SMTP authentication is not of relevance to the
-transfer of mail between servers that have no managerial connection with each
-other.
-
-.cindex "AUTH" "description of"
-Very briefly, the way SMTP authentication works is as follows:
-
-.ilist
-The server advertises a number of authentication &'mechanisms'& in response to
-the client's EHLO command.
-.next
-The client issues an AUTH command, naming a specific mechanism. The command
-may, optionally, contain some authentication data.
-.next
-The server may issue one or more &'challenges'&, to which the client must send
-appropriate responses. In simple authentication mechanisms, the challenges are
-just prompts for user names and passwords. The server does not have to issue
-any challenges &-- in some mechanisms the relevant data may all be transmitted
-with the AUTH command.
-.next
-The server either accepts or denies authentication.
-.next
-If authentication succeeds, the client may optionally make use of the AUTH
-option on the MAIL command to pass an authenticated sender in subsequent
-mail transactions. Authentication lasts for the remainder of the SMTP
-connection.
-.next
-If authentication fails, the client may give up, or it may try a different
-authentication mechanism, or it may try transferring mail over the
-unauthenticated connection.
-.endlist
-
-If you are setting up a client, and want to know which authentication
-mechanisms the server supports, you can use Telnet to connect to port 25 (the
-SMTP port) on the server, and issue an EHLO command. The response to this
-includes the list of supported mechanisms. For example:
-.display
-&`$ `&&*&`telnet server.example 25`&*&
-&`Trying 192.168.34.25...`&
-&`Connected to server.example.`&
-&`Escape character is &#x0027;^]&#x0027;.`&
-&`220 server.example ESMTP Exim 4.20 ...`&
-&*&`ehlo client.example`&*&
-&`250-server.example Hello client.example [10.8.4.5]`&
-&`250-SIZE 52428800`&
-&`250-PIPELINING`&
-&`250-AUTH PLAIN`&
-&`250 HELP`&
-.endd
-The second-last line of this example output shows that the server supports
-authentication using the PLAIN mechanism. In Exim, the different authentication
-mechanisms are configured by specifying &'authenticator'& drivers. Like the
-routers and transports, which authenticators are included in the binary is
-controlled by build-time definitions. The following are currently available,
-included by setting
-.code
-AUTH_CRAM_MD5=yes
-AUTH_CYRUS_SASL=yes
-AUTH_DOVECOT=yes
-AUTH_EXTERNAL=yes
-AUTH_GSASL=yes
-AUTH_HEIMDAL_GSSAPI=yes
-AUTH_PLAINTEXT=yes
-AUTH_SPA=yes
-AUTH_TLS=yes
-.endd
-in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5
-authentication mechanism (RFC 2195), and the second provides an interface to
-the Cyrus SASL authentication library.
-The third is an interface to Dovecot's authentication system, delegating the
-work via a socket interface.
-The fourth provides for negotiation of authentication done via non-SMTP means,
-as defined by RFC 4422 Appendix A.
-The fifth provides an interface to the GNU SASL authentication library, which
-provides mechanisms but typically not data sources.
-The sixth provides direct access to Heimdal GSSAPI, geared for Kerberos, but
-supporting setting a server keytab.
-The seventh can be configured to support
-the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is
-not formally documented, but used by several MUAs.
-The eighth authenticator
-supports Microsoft's &'Secure Password Authentication'& mechanism.
-The last is an Exim authenticator but not an SMTP one;
-instead it can use information from a TLS negotiation.
-
-The authenticators are configured using the same syntax as other drivers (see
-section &<<SECTfordricon>>&). If no authenticators are required, no
-authentication section need be present in the configuration file. Each
-authenticator can in principle have both server and client functions. When Exim
-is receiving SMTP mail, it is acting as a server; when it is sending out
-messages over SMTP, it is acting as a client. Authenticator configuration
-options are provided for use in both these circumstances.
-
-To make it clear which options apply to which situation, the prefixes
-&%server_%& and &%client_%& are used on option names that are specific to
-either the server or the client function, respectively. Server and client
-functions are disabled if none of their options are set. If an authenticator is
-to be used for both server and client functions, a single definition, using
-both sets of options, is required. For example:
-.code
-cram:
-  driver = cram_md5
-  public_name = CRAM-MD5
-  server_secret = ${if eq{$auth1}{ph10}{secret1}fail}
-  client_name = ph10
-  client_secret = secret2
-.endd
-The &%server_%& option is used when Exim is acting as a server, and the
-&%client_%& options when it is acting as a client.
-
-Descriptions of the individual authenticators are given in subsequent chapters.
-The remainder of this chapter covers the generic options for the
-authenticators, followed by general discussion of the way authentication works
-in Exim.
-
-&*Beware:*& the meaning of &$auth1$&, &$auth2$&, ... varies on a per-driver and
-per-mechanism basis.  Please read carefully to determine which variables hold
-account labels such as usercodes and which hold passwords or other
-authenticating data.
-
-Note that some mechanisms support two different identifiers for accounts: the
-&'authentication id'& and the &'authorization id'&.  The contractions &'authn'&
-and &'authz'& are commonly encountered.  The American spelling is standard here.
-Conceptually, authentication data such as passwords are tied to the identifier
-used to authenticate; servers may have rules to permit one user to act as a
-second user, so that after login the session is treated as though that second
-user had logged in.  That second user is the &'authorization id'&.  A robust
-configuration might confirm that the &'authz'& field is empty or matches the
-&'authn'& field.  Often this is just ignored.  The &'authn'& can be considered
-as verified data, the &'authz'& as an unverified request which the server might
-choose to honour.
-
-A &'realm'& is a text string, typically a domain name, presented by a server
-to a client to help it select an account and credentials to use.  In some
-mechanisms, the client and server provably agree on the realm, but clients
-typically can not treat the realm as secure data to be blindly trusted.
-
-
-
-.section "Generic options for authenticators" "SECID168"
-.cindex "authentication" "generic options"
-.cindex "options" "generic; for authenticators"
-
-.option client_condition authenticators string&!! unset
-When Exim is authenticating as a client, it skips any authenticator whose
-&%client_condition%& expansion yields &"0"&, &"no"&, or &"false"&. This can be
-used, for example, to skip plain text authenticators when the connection is not
-encrypted by a setting such as:
-.code
-client_condition = ${if !eq{$tls_out_cipher}{}}
-.endd
-
-
-.option client_set_id authenticators string&!! unset
-When client authentication succeeds, this condition is expanded; the
-result is used in the log lines for outbound messages.
-Typically it will be the user name used for authentication.
-
-
-.option driver authenticators string unset
-This option must always be set. It specifies which of the available
-authenticators is to be used.
-
-
-.option public_name authenticators string unset
-This option specifies the name of the authentication mechanism that the driver
-implements, and by which it is known to the outside world. These names should
-contain only upper case letters, digits, underscores, and hyphens (RFC 2222),
-but Exim in fact matches them caselessly. If &%public_name%& is not set, it
-defaults to the driver's instance name.
-
-
-.option server_advertise_condition authenticators string&!! unset
-When a server is about to advertise an authentication mechanism, the condition
-is expanded. If it yields the empty string, &"0"&, &"no"&, or &"false"&, the
-mechanism is not advertised.
-If the expansion fails, the mechanism is not advertised. If the failure was not
-forced, and was not caused by a lookup defer, the incident is logged.
-See section &<<SECTauthexiser>>& below for further discussion.
-
-
-.option server_condition authenticators string&!! unset
-This option must be set for a &%plaintext%& server authenticator, where it
-is used directly to control authentication. See section &<<SECTplainserver>>&
-for details.
-
-For the &(gsasl)& authenticator, this option is required for various
-mechanisms; see chapter &<<CHAPgsasl>>& for details.
-
-For the other authenticators, &%server_condition%& can be used as an additional
-authentication or authorization mechanism that is applied after the other
-authenticator conditions succeed. If it is set, it is expanded when the
-authenticator would otherwise return a success code. If the expansion is forced
-to fail, authentication fails. Any other expansion failure causes a temporary
-error code to be returned. If the result of a successful expansion is an empty
-string, &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
-expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds. For any
-other result, a temporary error code is returned, with the expanded string as
-the error text.
-
-
-.option server_debug_print authenticators string&!! unset
-If this option is set and authentication debugging is enabled (see the &%-d%&
-command line option), the string is expanded and included in the debugging
-output when the authenticator is run as a server. This can help with checking
-out the values of variables.
-If expansion of the string fails, the error message is written to the debugging
-output, and Exim carries on processing.
-
-
-.option server_set_id authenticators string&!! unset
-.vindex "&$authenticated_id$&"
-.vindex "&$authenticated_fail_id$&"
-When an Exim server successfully authenticates a client, this string is
-expanded using data from the authentication, and preserved for any incoming
-messages in the variable &$authenticated_id$&. It is also included in the log
-lines for incoming messages. For example, a user/password authenticator
-configuration might preserve the user name that was used to authenticate, and
-refer to it subsequently during delivery of the message.
-On a failing authentication the expansion result is instead saved in
-the &$authenticated_fail_id$& variable.
-If expansion fails, the option is ignored.
-
-
-.option server_mail_auth_condition authenticators string&!! unset
-This option allows a server to discard authenticated sender addresses supplied
-as part of MAIL commands in SMTP connections that are authenticated by the
-driver on which &%server_mail_auth_condition%& is set. The option is not used
-as part of the authentication process; instead its (unexpanded) value is
-remembered for later use.
-How it is used is described in the following section.
-
-
-
-
-
-.section "The AUTH parameter on MAIL commands" "SECTauthparamail"
-.cindex "authentication" "sender; authenticated"
-.cindex "AUTH" "on MAIL command"
-When a client supplied an AUTH= item on a MAIL command, Exim applies
-the following checks before accepting it as the authenticated sender of the
-message:
-
-.ilist
-If the connection is not using extended SMTP (that is, HELO was used rather
-than EHLO), the use of AUTH= is a syntax error.
-.next
-If the value of the AUTH= parameter is &"<>"&, it is ignored.
-.next
-.vindex "&$authenticated_sender$&"
-If &%acl_smtp_mailauth%& is defined, the ACL it specifies is run. While it is
-running, the value of &$authenticated_sender$& is set to the value obtained
-from the AUTH= parameter. If the ACL does not yield &"accept"&, the value of
-&$authenticated_sender$& is deleted. The &%acl_smtp_mailauth%& ACL may not
-return &"drop"& or &"discard"&. If it defers, a temporary error code (451) is
-given for the MAIL command.
-.next
-If &%acl_smtp_mailauth%& is not defined, the value of the AUTH= parameter
-is accepted and placed in &$authenticated_sender$& only if the client has
-authenticated.
-.next
-If the AUTH= value was accepted by either of the two previous rules, and
-the client has authenticated, and the authenticator has a setting for the
-&%server_mail_auth_condition%&, the condition is checked at this point. The
-valued that was saved from the authenticator is expanded. If the expansion
-fails, or yields an empty string, &"0"&, &"no"&, or &"false"&, the value of
-&$authenticated_sender$& is deleted. If the expansion yields any other value,
-the value of &$authenticated_sender$& is retained and passed on with the
-message.
-.endlist
-
-
-When &$authenticated_sender$& is set for a message, it is passed on to other
-hosts to which Exim authenticates as a client. Do not confuse this value with
-&$authenticated_id$&, which is a string obtained from the authentication
-process, and which is not usually a complete email address.
-
-.vindex "&$sender_address$&"
-Whenever an AUTH= value is ignored, the incident is logged. The ACL for
-MAIL, if defined, is run after AUTH= is accepted or ignored. It can
-therefore make use of &$authenticated_sender$&. The converse is not true: the
-value of &$sender_address$& is not yet set up when the &%acl_smtp_mailauth%&
-ACL is run.
-
-
-
-.section "Authentication on an Exim server" "SECTauthexiser"
-.cindex "authentication" "on an Exim server"
-When Exim receives an EHLO command, it advertises the public names of those
-authenticators that are configured as servers, subject to the following
-conditions:
-
-.ilist
-The client host must match &%auth_advertise_hosts%& (default *).
-.next
-It the &%server_advertise_condition%& option is set, its expansion must not
-yield the empty string, &"0"&, &"no"&, or &"false"&.
-.endlist
-
-The order in which the authenticators are defined controls the order in which
-the mechanisms are advertised.
-
-Some mail clients (for example, some versions of Netscape) require the user to
-provide a name and password for authentication whenever AUTH is advertised,
-even though authentication may not in fact be needed (for example, Exim may be
-set up to allow unconditional relaying from the client by an IP address check).
-You can make such clients more friendly by not advertising AUTH to them.
-For example, if clients on the 10.9.8.0/24 network are permitted (by the ACL
-that runs for RCPT) to relay without authentication, you should set
-.code
-auth_advertise_hosts = ! 10.9.8.0/24
-.endd
-so that no authentication mechanisms are advertised to them.
-
-The &%server_advertise_condition%& controls the advertisement of individual
-authentication mechanisms. For example, it can be used to restrict the
-advertisement of a particular mechanism to encrypted connections, by a setting
-such as:
-.code
-server_advertise_condition = ${if eq{$tls_in_cipher}{}{no}{yes}}
-.endd
-.vindex "&$tls_in_cipher$&"
-If the session is encrypted, &$tls_in_cipher$& is not empty, and so the expansion
-yields &"yes"&, which allows the advertisement to happen.
-
-When an Exim server receives an AUTH command from a client, it rejects it
-immediately if AUTH was not advertised in response to an earlier EHLO
-command. This is the case if
-
-.ilist
-The client host does not match &%auth_advertise_hosts%&; or
-.next
-No authenticators are configured with server options; or
-.next
-Expansion of &%server_advertise_condition%& blocked the advertising of all the
-server authenticators.
-.endlist
-
-
-Otherwise, Exim runs the ACL specified by &%acl_smtp_auth%& in order
-to decide whether to accept the command. If &%acl_smtp_auth%& is not set,
-AUTH is accepted from any client host.
-
-If AUTH is not rejected by the ACL, Exim searches its configuration for a
-server authentication mechanism that was advertised in response to EHLO and
-that matches the one named in the AUTH command. If it finds one, it runs
-the appropriate authentication protocol, and authentication either succeeds or
-fails. If there is no matching advertised mechanism, the AUTH command is
-rejected with a 504 error.
-
-.vindex "&$received_protocol$&"
-.vindex "&$sender_host_authenticated$&"
-When a message is received from an authenticated host, the value of
-&$received_protocol$& is set to &"esmtpa"& or &"esmtpsa"& instead of &"esmtp"&
-or &"esmtps"&, and &$sender_host_authenticated$& contains the name (not the
-public name) of the authenticator driver that successfully authenticated the
-client from which the message was received. This variable is empty if there was
-no successful authentication.
-
-.cindex authentication "expansion item"
-Successful authentication sets up information used by the
-&%authresults%& expansion item.
-
-
-
-
-.section "Testing server authentication" "SECID169"
-.cindex "authentication" "testing a server"
-.cindex "AUTH" "testing a server"
-.cindex "base64 encoding" "creating authentication test data"
-Exim's &%-bh%& option can be useful for testing server authentication
-configurations. The data for the AUTH command has to be sent using base64
-encoding. A quick way to produce such data for testing is the following Perl
-script:
-.code
-use MIME::Base64;
-printf ("%s", encode_base64(eval "\"$ARGV[0]\""));
-.endd
-.cindex "binary zero" "in authentication data"
-This interprets its argument as a Perl string, and then encodes it. The
-interpretation as a Perl string allows binary zeros, which are required for
-some kinds of authentication, to be included in the data. For example, a
-command line to run this script on such data might be
-.code
-encode '\0user\0password'
-.endd
-Note the use of single quotes to prevent the shell interpreting the
-backslashes, so that they can be interpreted by Perl to specify characters
-whose code value is zero.
-
-&*Warning 1*&: If either of the user or password strings starts with an octal
-digit, you must use three zeros instead of one after the leading backslash. If
-you do not, the octal digit that starts your string will be incorrectly
-interpreted as part of the code for the first character.
-
-&*Warning 2*&: If there are characters in the strings that Perl interprets
-specially, you must use a Perl escape to prevent them being misinterpreted. For
-example, a command such as
-.code
-encode '\0user@domain.com\0pas$$word'
-.endd
-gives an incorrect answer because of the unescaped &"@"& and &"$"& characters.
-
-If you have the &%mimencode%& command installed, another way to do produce
-base64-encoded strings is to run the command
-.code
-echo -e -n `\0user\0password' | mimencode
-.endd
-The &%-e%& option of &%echo%& enables the interpretation of backslash escapes
-in the argument, and the &%-n%& option specifies no newline at the end of its
-output. However, not all versions of &%echo%& recognize these options, so you
-should check your version before relying on this suggestion.
-
-
-
-.section "Authentication by an Exim client" "SECID170"
-.cindex "authentication" "on an Exim client"
-The &(smtp)& transport has two options called &%hosts_require_auth%& and
-&%hosts_try_auth%&. When the &(smtp)& transport connects to a server that
-announces support for authentication, and the host matches an entry in either
-of these options, Exim (as a client) tries to authenticate as follows:
-
-.ilist
-For each authenticator that is configured as a client, in the order in which
-they are defined in the configuration, it searches the authentication
-mechanisms announced by the server for one whose name matches the public name
-of the authenticator.
-.next
-.vindex "&$host$&"
-.vindex "&$host_address$&"
-When it finds one that matches, it runs the authenticator's client code. The
-variables &$host$& and &$host_address$& are available for any string expansions
-that the client might do. They are set to the server's name and IP address. If
-any expansion is forced to fail, the authentication attempt is abandoned, and
-Exim moves on to the next authenticator. Otherwise an expansion failure causes
-delivery to be deferred.
-.next
-If the result of the authentication attempt is a temporary error or a timeout,
-Exim abandons trying to send the message to the host for the moment. It will
-try again later. If there are any backup hosts available, they are tried in the
-usual way.
-.next
-If the response to authentication is a permanent error (5&'xx'& code), Exim
-carries on searching the list of authenticators and tries another one if
-possible. If all authentication attempts give permanent errors, or if there are
-no attempts because no mechanisms match (or option expansions force failure),
-what happens depends on whether the host matches &%hosts_require_auth%& or
-&%hosts_try_auth%&. In the first case, a temporary error is generated, and
-delivery is deferred. The error can be detected in the retry rules, and thereby
-turned into a permanent error if you wish. In the second case, Exim tries to
-deliver the message unauthenticated.
-.endlist
-
-Note that the hostlist test for whether to do authentication can be
-confused if name-IP lookups change between the time the peer is decided
-upon and the time that the transport runs.  For example, with a manualroute
-router given a host name, and with DNS "round-robin" used by that name: if
-the local resolver cache times out between the router and the transport
-running, the transport may get an IP for the name for its authentication
-check which does not match the connection peer IP.
-No authentication will then be done, despite the names being identical.
-
-For such cases use a separate transport which always authenticates.
-
-.cindex "AUTH" "on MAIL command"
-When Exim has authenticated itself to a remote server, it adds the AUTH
-parameter to the MAIL commands it sends, if it has an authenticated sender for
-the message. If the message came from a remote host, the authenticated sender
-is the one that was receiving on an incoming MAIL command, provided that the
-incoming connection was authenticated and the &%server_mail_auth%& condition
-allowed the authenticated sender to be retained. If a local process calls Exim
-to send a message, the sender address that is built from the login name and
-&%qualify_domain%& is treated as authenticated. However, if the
-&%authenticated_sender%& option is set on the &(smtp)& transport, it overrides
-the authenticated sender that was received with the message.
-.ecindex IIDauthconf1
-.ecindex IIDauthconf2
-
-
-
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "The plaintext authenticator" "CHAPplaintext"
-.scindex IIDplaiauth1 "&(plaintext)& authenticator"
-.scindex IIDplaiauth2 "authenticators" "&(plaintext)&"
-The &(plaintext)& authenticator can be configured to support the PLAIN and
-LOGIN authentication mechanisms, both of which transfer authentication data as
-plain (unencrypted) text (though base64 encoded). The use of plain text is a
-security risk; you are strongly advised to insist on the use of SMTP encryption
-(see chapter &<<CHAPTLS>>&) if you use the PLAIN or LOGIN mechanisms. If you do
-use unencrypted plain text, you should not use the same passwords for SMTP
-connections as you do for login accounts.
-
-.section "Avoiding cleartext use" "SECTplain_TLS"
-The following generic option settings will disable &(plaintext)& authenticators when
-TLS is not being used:
-.code
-  server_advertise_condition = ${if def:tls_in_cipher }
-  client_condition =           ${if def:tls_out_cipher}
-.endd
-
-&*Note*&: a plaintext SMTP AUTH done inside TLS is not vulnerable to casual snooping,
-but is still vulnerable to a Man In The Middle attack unless certificates
-(including their names) have been properly verified.
-
-.section "Plaintext server options" "SECID171"
-.cindex "options" "&(plaintext)& authenticator (server)"
-When configured as a server, &(plaintext)& uses the following options:
-
-.option server_condition authenticators string&!! unset
-This is actually a global authentication option, but it must be set in order to
-configure the &(plaintext)& driver as a server. Its use is described below.
-
-.option server_prompts plaintext "string list&!!" unset
-The contents of this option, after expansion, must be a colon-separated list of
-prompt strings. If expansion fails, a temporary authentication rejection is
-given.
-
-.section "Using plaintext in a server" "SECTplainserver"
-.cindex "AUTH" "in &(plaintext)& authenticator"
-.cindex "binary zero" "in &(plaintext)& authenticator"
-.cindex "numerical variables (&$1$& &$2$& etc)" &&&
-        "in &(plaintext)& authenticator"
-.vindex "&$auth1$&, &$auth2$&, etc"
-.cindex "base64 encoding" "in &(plaintext)& authenticator"
-
-When running as a server, &(plaintext)& performs the authentication test by
-expanding a string. The data sent by the client with the AUTH command, or in
-response to subsequent prompts, is base64 encoded, and so may contain any byte
-values when decoded. If any data is supplied with the command, it is treated as
-a list of strings, separated by NULs (binary zeros), the first three of which
-are placed in the expansion variables &$auth1$&, &$auth2$&, and &$auth3$&
-(neither LOGIN nor PLAIN uses more than three strings).
-
-For compatibility with previous releases of Exim, the values are also placed in
-the expansion variables &$1$&, &$2$&, and &$3$&. However, the use of these
-variables for this purpose is now deprecated, as it can lead to confusion in
-string expansions that also use them for other things.
-
-If there are more strings in &%server_prompts%& than the number of strings
-supplied with the AUTH command, the remaining prompts are used to obtain more
-data. Each response from the client may be a list of NUL-separated strings.
-
-.vindex "&$authenticated_id$&"
-Once a sufficient number of data strings have been received,
-&%server_condition%& is expanded. If the expansion is forced to fail,
-authentication fails. Any other expansion failure causes a temporary error code
-to be returned. If the result of a successful expansion is an empty string,
-&"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
-expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
-generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
-For any other result, a temporary error code is returned, with the expanded
-string as the error text.
-
-&*Warning*&: If you use a lookup in the expansion to find the user's
-password, be sure to make the authentication fail if the user is unknown.
-There are good and bad examples at the end of the next section.
-
-
-
-.section "The PLAIN authentication mechanism" "SECID172"
-.cindex "PLAIN authentication mechanism"
-.cindex authentication PLAIN
-.cindex "binary zero" "in &(plaintext)& authenticator"
-The PLAIN authentication mechanism (RFC 2595) specifies that three strings be
-sent as one item of data (that is, one combined string containing two NUL
-separators). The data is sent either as part of the AUTH command, or
-subsequently in response to an empty prompt from the server.
-
-The second and third strings are a user name and a corresponding password.
-Using a single fixed user name and password as an example, this could be
-configured as follows:
-.code
-fixed_plain:
-  driver = plaintext
-  public_name = PLAIN
-  server_prompts = :
-  server_condition = \
-    ${if and {{eq{$auth2}{username}}{eq{$auth3}{mysecret}}}}
-  server_set_id = $auth2
-.endd
-Note that the default result strings from &%if%& (&"true"& or an empty string)
-are exactly what we want here, so they need not be specified. Obviously, if the
-password contains expansion-significant characters such as dollar, backslash,
-or closing brace, they have to be escaped.
-
-The &%server_prompts%& setting specifies a single, empty prompt (empty items at
-the end of a string list are ignored). If all the data comes as part of the
-AUTH command, as is commonly the case, the prompt is not used. This
-authenticator is advertised in the response to EHLO as
-.code
-250-AUTH PLAIN
-.endd
-and a client host can authenticate itself by sending the command
-.code
-AUTH PLAIN AHVzZXJuYW1lAG15c2VjcmV0
-.endd
-As this contains three strings (more than the number of prompts), no further
-data is required from the client. Alternatively, the client may just send
-.code
-AUTH PLAIN
-.endd
-to initiate authentication, in which case the server replies with an empty
-prompt. The client must respond with the combined data string.
-
-The data string is base64 encoded, as required by the RFC. This example,
-when decoded, is <&'NUL'&>&`username`&<&'NUL'&>&`mysecret`&, where <&'NUL'&>
-represents a zero byte. This is split up into three strings, the first of which
-is empty. The &%server_condition%& option in the authenticator checks that the
-second two are &`username`& and &`mysecret`& respectively.
-
-Having just one fixed user name and password, as in this example, is not very
-realistic, though for a small organization with only a handful of
-authenticating clients it could make sense.
-
-A more sophisticated instance of this authenticator could use the user name in
-&$auth2$& to look up a password in a file or database, and maybe do an encrypted
-comparison (see &%crypteq%& in chapter &<<CHAPexpand>>&). Here is a example of
-this approach, where the passwords are looked up in a DBM file. &*Warning*&:
-This is an incorrect example:
-.code
-server_condition = \
-  ${if eq{$auth3}{${lookup{$auth2}dbm{/etc/authpwd}}}}
-.endd
-The expansion uses the user name (&$auth2$&) as the key to look up a password,
-which it then compares to the supplied password (&$auth3$&). Why is this example
-incorrect? It works fine for existing users, but consider what happens if a
-non-existent user name is given. The lookup fails, but as no success/failure
-strings are given for the lookup, it yields an empty string. Thus, to defeat
-the authentication, all a client has to do is to supply a non-existent user
-name and an empty password. The correct way of writing this test is:
-.code
-server_condition = ${lookup{$auth2}dbm{/etc/authpwd}\
-  {${if eq{$value}{$auth3}}} {false}}
-.endd
-In this case, if the lookup succeeds, the result is checked; if the lookup
-fails, &"false"& is returned and authentication fails. If &%crypteq%& is being
-used instead of &%eq%&, the first example is in fact safe, because &%crypteq%&
-always fails if its second argument is empty. However, the second way of
-writing the test makes the logic clearer.
-
-
-.section "The LOGIN authentication mechanism" "SECID173"
-.cindex "LOGIN authentication mechanism"
-.cindex authentication LOGIN
-The LOGIN authentication mechanism is not documented in any RFC, but is in use
-in a number of programs. No data is sent with the AUTH command. Instead, a
-user name and password are supplied separately, in response to prompts. The
-plaintext authenticator can be configured to support this as in this example:
-.code
-fixed_login:
-  driver = plaintext
-  public_name = LOGIN
-  server_prompts = User Name : Password
-  server_condition = \
-    ${if and {{eq{$auth1}{username}}{eq{$auth2}{mysecret}}}}
-  server_set_id = $auth1
-.endd
-Because of the way plaintext operates, this authenticator accepts data supplied
-with the AUTH command (in contravention of the specification of LOGIN), but
-if the client does not supply it (as is the case for LOGIN clients), the prompt
-strings are used to obtain two data items.
-
-Some clients are very particular about the precise text of the prompts. For
-example, Outlook Express is reported to recognize only &"Username:"& and
-&"Password:"&. Here is an example of a LOGIN authenticator that uses those
-strings. It uses the &%ldapauth%& expansion condition to check the user
-name and password by binding to an LDAP server:
-.code
-login:
-  driver = plaintext
-  public_name = LOGIN
-  server_prompts = Username:: : Password::
-  server_condition = ${if and{{ \
-    !eq{}{$auth1} }{ \
-    ldapauth{\
-      user="uid=${quote_ldap_dn:$auth1},ou=people,o=example.org" \
-      pass=${quote:$auth2} \
-      ldap://ldap.example.org/} }} }
-  server_set_id = uid=$auth1,ou=people,o=example.org
-.endd
-We have to check that the username is not empty before using it, because LDAP
-does not permit empty DN components. We must also use the &%quote_ldap_dn%&
-operator to correctly quote the DN for authentication. However, the basic
-&%quote%& operator, rather than any of the LDAP quoting operators, is the
-correct one to use for the password, because quoting is needed only to make
-the password conform to the Exim syntax. At the LDAP level, the password is an
-uninterpreted string.
-
-
-.section "Support for different kinds of authentication" "SECID174"
-A number of string expansion features are provided for the purpose of
-interfacing to different ways of user authentication. These include checking
-traditionally encrypted passwords from &_/etc/passwd_& (or equivalent), PAM,
-Radius, &%ldapauth%&, &'pwcheck'&, and &'saslauthd'&. For details see section
-&<<SECTexpcond>>&.
-
-
-
-
-.section "Using plaintext in a client" "SECID175"
-.cindex "options" "&(plaintext)& authenticator (client)"
-The &(plaintext)& authenticator has two client options:
-
-.option client_ignore_invalid_base64 plaintext boolean false
-If the client receives a server prompt that is not a valid base64 string,
-authentication is abandoned by default. However, if this option is set true,
-the error in the challenge is ignored and the client sends the response as
-usual.
-
-.option client_send plaintext string&!! unset
-The string is a colon-separated list of authentication data strings. Each
-string is independently expanded before being sent to the server. The first
-string is sent with the AUTH command; any more strings are sent in response
-to prompts from the server. Before each string is expanded, the value of the
-most recent prompt is placed in the next &$auth$&<&'n'&> variable, starting
-with &$auth1$& for the first prompt. Up to three prompts are stored in this
-way. Thus, the prompt that is received in response to sending the first string
-(with the AUTH command) can be used in the expansion of the second string, and
-so on. If an invalid base64 string is received when
-&%client_ignore_invalid_base64%& is set, an empty string is put in the
-&$auth$&<&'n'&> variable.
-
-&*Note*&: You cannot use expansion to create multiple strings, because
-splitting takes priority and happens first.
-
-Because the PLAIN authentication mechanism requires NUL (binary zero) bytes in
-the data, further processing is applied to each string before it is sent. If
-there are any single circumflex characters in the string, they are converted to
-NULs. Should an actual circumflex be required as data, it must be doubled in
-the string.
-
-This is an example of a client configuration that implements the PLAIN
-authentication mechanism with a fixed user name and password:
-.code
-fixed_plain:
-  driver = plaintext
-  public_name = PLAIN
-  client_send = ^username^mysecret
-.endd
-The lack of colons means that the entire text is sent with the AUTH
-command, with the circumflex characters converted to NULs. A similar example
-that uses the LOGIN mechanism is:
-.code
-fixed_login:
-  driver = plaintext
-  public_name = LOGIN
-  client_send = : username : mysecret
-.endd
-The initial colon means that the first string is empty, so no data is sent with
-the AUTH command itself. The remaining strings are sent in response to
-prompts.
-.ecindex IIDplaiauth1
-.ecindex IIDplaiauth2
-
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "The cram_md5 authenticator" "CHID9"
-.scindex IIDcramauth1 "&(cram_md5)& authenticator"
-.scindex IIDcramauth2 "authenticators" "&(cram_md5)&"
-.cindex "CRAM-MD5 authentication mechanism"
-.cindex authentication CRAM-MD5
-The CRAM-MD5 authentication mechanism is described in RFC 2195. The server
-sends a challenge string to the client, and the response consists of a user
-name and the CRAM-MD5 digest of the challenge string combined with a secret
-string (password) which is known to both server and client. Thus, the secret
-is not sent over the network as plain text, which makes this authenticator more
-secure than &(plaintext)&. However, the downside is that the secret has to be
-available in plain text at either end.
-
-
-.section "Using cram_md5 as a server" "SECID176"
-.cindex "options" "&(cram_md5)& authenticator (server)"
-This authenticator has one server option, which must be set to configure the
-authenticator as a server:
-
-.option server_secret cram_md5 string&!! unset
-.cindex "numerical variables (&$1$& &$2$& etc)" "in &(cram_md5)& authenticator"
-When the server receives the client's response, the user name is placed in
-the expansion variable &$auth1$&, and &%server_secret%& is expanded to
-obtain the password for that user. The server then computes the CRAM-MD5 digest
-that the client should have sent, and checks that it received the correct
-string. If the expansion of &%server_secret%& is forced to fail, authentication
-fails. If the expansion fails for some other reason, a temporary error code is
-returned to the client.
-
-For compatibility with previous releases of Exim, the user name is also placed
-in &$1$&. However, the use of this variables for this purpose is now
-deprecated, as it can lead to confusion in string expansions that also use
-numeric variables for other things.
-
-For example, the following authenticator checks that the user name given by the
-client is &"ph10"&, and if so, uses &"secret"& as the password. For any other
-user name, authentication fails.
-.code
-fixed_cram:
-  driver = cram_md5
-  public_name = CRAM-MD5
-  server_secret = ${if eq{$auth1}{ph10}{secret}fail}
-  server_set_id = $auth1
-.endd
-.vindex "&$authenticated_id$&"
-If authentication succeeds, the setting of &%server_set_id%& preserves the user
-name in &$authenticated_id$&. A more typical configuration might look up the
-secret string in a file, using the user name as the key. For example:
-.code
-lookup_cram:
-  driver = cram_md5
-  public_name = CRAM-MD5
-  server_secret = ${lookup{$auth1}lsearch{/etc/authpwd}\
-                  {$value}fail}
-  server_set_id = $auth1
-.endd
-Note that this expansion explicitly forces failure if the lookup fails
-because &$auth1$& contains an unknown user name.
-
-As another example, if you wish to re-use a Cyrus SASL sasldb2 file without
-using the relevant libraries, you need to know the realm to specify in the
-lookup and then ask for the &"userPassword"& attribute for that user in that
-realm, with:
-.code
-cyrusless_crammd5:
-  driver = cram_md5
-  public_name = CRAM-MD5
-  server_secret = ${lookup{$auth1:mail.example.org:userPassword}\
-                  dbmjz{/etc/sasldb2}{$value}fail}
-  server_set_id = $auth1
-.endd
-
-.section "Using cram_md5 as a client" "SECID177"
-.cindex "options" "&(cram_md5)& authenticator (client)"
-When used as a client, the &(cram_md5)& authenticator has two options:
-
-
-
-.option client_name cram_md5 string&!! "the primary host name"
-This string is expanded, and the result used as the user name data when
-computing the response to the server's challenge.
-
-
-.option client_secret cram_md5 string&!! unset
-This option must be set for the authenticator to work as a client. Its value is
-expanded and the result used as the secret string when computing the response.
-
-
-.vindex "&$host$&"
-.vindex "&$host_address$&"
-Different user names and secrets can be used for different servers by referring
-to &$host$& or &$host_address$& in the options. Forced failure of either
-expansion string is treated as an indication that this authenticator is not
-prepared to handle this case. Exim moves on to the next configured client
-authenticator. Any other expansion failure causes Exim to give up trying to
-send the message to the current server.
-
-A simple example configuration of a &(cram_md5)& authenticator, using fixed
-strings, is:
-.code
-fixed_cram:
-  driver = cram_md5
-  public_name = CRAM-MD5
-  client_name = ph10
-  client_secret = secret
-.endd
-.ecindex IIDcramauth1
-.ecindex IIDcramauth2
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "The cyrus_sasl authenticator" "CHID10"
-.scindex IIDcyrauth1 "&(cyrus_sasl)& authenticator"
-.scindex IIDcyrauth2 "authenticators" "&(cyrus_sasl)&"
-.cindex "Cyrus" "SASL library"
-.cindex "Kerberos"
-The code for this authenticator was provided by Matthew Byng-Maddick while
-at A L Digital Ltd.
-
-The &(cyrus_sasl)& authenticator provides server support for the Cyrus SASL
-library implementation of the RFC 2222 (&"Simple Authentication and Security
-Layer"&). This library supports a number of authentication mechanisms,
-including PLAIN and LOGIN, but also several others that Exim does not support
-directly. In particular, there is support for Kerberos authentication.
-
-The &(cyrus_sasl)& authenticator provides a gatewaying mechanism directly to
-the Cyrus interface, so if your Cyrus library can do, for example, CRAM-MD5,
-then so can the &(cyrus_sasl)& authenticator. By default it uses the public
-name of the driver to determine which mechanism to support.
-
-Where access to some kind of secret file is required, for example, in GSSAPI
-or CRAM-MD5, it is worth noting that the authenticator runs as the Exim
-user, and that the Cyrus SASL library has no way of escalating privileges
-by default. You may also find you need to set environment variables,
-depending on the driver you are using.
-
-The application name provided by Exim is &"exim"&, so various SASL options may
-be set in &_exim.conf_& in your SASL directory. If you are using GSSAPI for
-Kerberos, note that because of limitations in the GSSAPI interface,
-changing the server keytab might need to be communicated down to the Kerberos
-layer independently. The mechanism for doing so is dependent upon the Kerberos
-implementation.
-
-For example, for older releases of Heimdal, the environment variable KRB5_KTNAME
-may be set to point to an alternative keytab file. Exim will pass this
-variable through from its own inherited environment when started as root or the
-Exim user. The keytab file needs to be readable by the Exim user.
-With newer releases of Heimdal, a setuid Exim may cause Heimdal to discard the
-environment variable.  In practice, for those releases, the Cyrus authenticator
-is not a suitable interface for GSSAPI (Kerberos) support.  Instead, consider
-the &(heimdal_gssapi)& authenticator, described in chapter &<<CHAPheimdalgss>>&
-
-
-.section "Using cyrus_sasl as a server" "SECID178"
-The &(cyrus_sasl)& authenticator has four private options. It puts the username
-(on a successful authentication) into &$auth1$&. For compatibility with
-previous releases of Exim, the username is also placed in &$1$&. However, the
-use of this variable for this purpose is now deprecated, as it can lead to
-confusion in string expansions that also use numeric variables for other
-things.
-
-
-.option server_hostname cyrus_sasl string&!! "see below"
-This option selects the hostname that is used when communicating with the
-library. The default value is &`$primary_hostname`&. It is up to the underlying
-SASL plug-in what it does with this data.
-
-
-.option server_mech cyrus_sasl string "see below"
-This option selects the authentication mechanism this driver should use. The
-default is the value of the generic &%public_name%& option. This option allows
-you to use a different underlying mechanism from the advertised name. For
-example:
-.code
-sasl:
-  driver = cyrus_sasl
-  public_name = X-ANYTHING
-  server_mech = CRAM-MD5
-  server_set_id = $auth1
-.endd
-
-.option server_realm cyrus_sasl string&!! unset
-This specifies the SASL realm that the server claims to be in.
-
-
-.option server_service cyrus_sasl string &`smtp`&
-This is the SASL service that the server claims to implement.
-
-
-For straightforward cases, you do not need to set any of the authenticator's
-private options. All you need to do is to specify an appropriate mechanism as
-the public name. Thus, if you have a SASL library that supports CRAM-MD5 and
-PLAIN, you could have two authenticators as follows:
-.code
-sasl_cram_md5:
-  driver = cyrus_sasl
-  public_name = CRAM-MD5
-  server_set_id = $auth1
-
-sasl_plain:
-  driver = cyrus_sasl
-  public_name = PLAIN
-  server_set_id = $auth2
-.endd
-Cyrus SASL does implement the LOGIN authentication method, even though it is
-not a standard method. It is disabled by default in the source distribution,
-but it is present in many binary distributions.
-.ecindex IIDcyrauth1
-.ecindex IIDcyrauth2
-
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-.chapter "The dovecot authenticator" "CHAPdovecot"
-.scindex IIDdcotauth1 "&(dovecot)& authenticator"
-.scindex IIDdcotauth2 "authenticators" "&(dovecot)&"
-This authenticator is an interface to the authentication facility of the
-Dovecot 2 POP/IMAP server, which can support a number of authentication methods.
-Note that Dovecot must be configured to use auth-client not auth-userdb.
-If you are using Dovecot to authenticate POP/IMAP clients, it might be helpful
-to use the same mechanisms for SMTP authentication. This is a server
-authenticator only. There is only one option:
-
-.option server_socket dovecot string unset
-
-This option must specify the UNIX socket that is the interface to Dovecot
-authentication. The &%public_name%& option must specify an authentication
-mechanism that Dovecot is configured to support. You can have several
-authenticators for different mechanisms. For example:
-.code
-dovecot_plain:
-  driver = dovecot
-  public_name = PLAIN
-  server_socket = /var/run/dovecot/auth-client
-  server_set_id = $auth1
-
-dovecot_ntlm:
-  driver = dovecot
-  public_name = NTLM
-  server_socket = /var/run/dovecot/auth-client
-  server_set_id = $auth1
-.endd
-If the SMTP connection is encrypted, or if &$sender_host_address$& is equal to
-&$received_ip_address$& (that is, the connection is local), the &"secured"&
-option is passed in the Dovecot authentication command. If, for a TLS
-connection, a client certificate has been verified, the &"valid-client-cert"&
-option is passed. When authentication succeeds, the identity of the user
-who authenticated is placed in &$auth1$&.
-
-.new
-The Dovecot configuration to match the above wil look
-something like:
-.code
-conf.d/10-master.conf :-
-
-service auth {
-...
-#SASL
-  unix_listener auth-client {
-    mode = 0660
-    user = mail
-  }
-...
-}
-
-conf.d/10-auth.conf :-
-
-auth_mechanisms = plain login ntlm
-.endd
-.wen
-
-.ecindex IIDdcotauth1
-.ecindex IIDdcotauth2
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-.chapter "The gsasl authenticator" "CHAPgsasl"
-.scindex IIDgsaslauth1 "&(gsasl)& authenticator"
-.scindex IIDgsaslauth2 "authenticators" "&(gsasl)&"
-.cindex "authentication" "GNU SASL"
-.cindex "authentication" "SASL"
-.cindex "authentication" "EXTERNAL"
-.cindex "authentication" "ANONYMOUS"
-.cindex "authentication" "PLAIN"
-.cindex "authentication" "LOGIN"
-.cindex "authentication" "DIGEST-MD5"
-.cindex "authentication" "CRAM-MD5"
-.cindex "authentication" "SCRAM family"
-The &(gsasl)& authenticator provides integration for the GNU SASL
-library and the mechanisms it provides.  This is new as of the 4.80 release
-and there are a few areas where the library does not let Exim smoothly
-scale to handle future authentication mechanisms, so no guarantee can be
-made that any particular new authentication mechanism will be supported
-without code changes in Exim.
-
-.new
-The library is expected to add support in an upcoming
-realease for the SCRAM-SHA-256 method.
-The macro _HAVE_AUTH_GSASL_SCRAM_SHA_256 will be defined
-when this happens.
-
-
-.option client_authz gsasl string&!! unset
-This option can be used to supply an &'authorization id'&
-which is different to the &'authentication_id'& provided
-by &%client_username%& option.
-If unset or (after expansion) empty it is not used,
-which is the common case.
-
-.option client_channelbinding gsasl boolean false
-See &%server_channelbinding%& below.
-
-.option client_password gsasl string&!! unset
-This option is exapanded before use, and should result in
-the password to be used, in clear.
-
-.option client_username gsasl string&!! unset
-This option is exapanded before use, and should result in
-the account name to be used.
-.wen
-
-.new
-.option client_spassword gsasl string&!! unset
-If a SCRAM mechanism is being used and this option is set
-it is used in preference to &%client_password%&.
-The value after expansion should be
-a 40 (for SHA-1) or 64 (for SHA-256) character string
-with the PBKDF2-prepared password, hex-encoded.
-Note that this value will depend on the salt and iteration-count
-supplied by the server.
-.wen
-
-
-
-.option server_channelbinding gsasl boolean false
-Do not set this true and rely on the properties
-without consulting a cryptographic engineer.
-
-Some authentication mechanisms are able to use external context at both ends
-of the session to bind the authentication to that context, and fail the
-authentication process if that context differs.  Specifically, some TLS
-ciphersuites can provide identifying information about the cryptographic
-context.
-
-This should have meant that certificate identity and verification becomes a
-non-issue, as a man-in-the-middle attack will cause the correct client and
-server to see different identifiers and authentication will fail.
-
-.new
-This is
-only usable by mechanisms which support "channel binding"; at time of
-writing, that's the SCRAM family.
-When using this feature the "-PLUS" variants of the method names need to be used.
-.wen
-
-This defaults off to ensure smooth upgrade across Exim releases, in case
-this option causes some clients to start failing.  Some future release
-of Exim might have switched the default to be true.
-
-However, Channel Binding in TLS has proven to be vulnerable in current versions.
-Do not plan to rely upon this feature for security, ever, without consulting
-with a subject matter expert (a cryptographic engineer).
-
-
-.option server_hostname gsasl string&!! "see below"
-This option selects the hostname that is used when communicating with the
-library. The default value is &`$primary_hostname`&.
-Some mechanisms will use this data.
-
-
-.option server_mech gsasl string "see below"
-This option selects the authentication mechanism this driver should use. The
-default is the value of the generic &%public_name%& option. This option allows
-you to use a different underlying mechanism from the advertised name. For
-example:
-.code
-sasl:
-  driver = gsasl
-  public_name = X-ANYTHING
-  server_mech = CRAM-MD5
-  server_set_id = $auth1
-.endd
-
-
-.option server_password gsasl string&!! unset
-Various mechanisms need access to the cleartext password on the server, so
-that proof-of-possession can be demonstrated on the wire, without sending
-the password itself.
-
-The data available for lookup varies per mechanism.
-In all cases, &$auth1$& is set to the &'authentication id'&.
-The &$auth2$& variable will always be the &'authorization id'& (&'authz'&)
-if available, else the empty string.
-The &$auth3$& variable will always be the &'realm'& if available,
-else the empty string.
-
-A forced failure will cause authentication to defer.
-
-If using this option, it may make sense to set the &%server_condition%&
-option to be simply "true".
-
-
-.option server_realm gsasl string&!! unset
-This specifies the SASL realm that the server claims to be in.
-Some mechanisms will use this data.
-
-
-.option server_scram_iter gsasl string&!! 4096
-This option provides data for the SCRAM family of mechanisms.
-.new
-The &$auth1$&, &$auth2$& and &$auth3$& variables are available
-when this option is expanded.
-
-The result of expansion should be a decimal number,
-and represents both a lower-bound on the security, and
-a compute cost factor imposed on the client
-(if it does not cache results, or the server changes
-either the iteration count or the salt).
-A minimum value of 4096 is required by the standards
-for all current SCRAM mechanism variants.
-.wen
-
-.option server_scram_salt gsasl string&!! unset
-This option provides data for the SCRAM family of mechanisms.
-.new
-The &$auth1$&, &$auth2$& and &$auth3$& variables are available
-when this option is expanded.
-The value should be a base64-encoded string,
-of random data typically 4-to-16 bytes long.
-If unset or empty after expansion the library will provides a value for the
-protocol conversation.
-.wen
-
-
-.new
-.option server_key gsasl string&!! unset
-.option server_skey gsasl string&!! unset
-These options can be used for the SCRAM family of mechanisms
-to provide stored information related to a password,
-the storage of which is preferable to plaintext.
-
-&%server_key%& is the value defined in the SCRAM standards as ServerKey;
-&%server_skey%& is StoredKey.
-
-They are only available for version 1.9.0 (or later) of the gsasl library.
-When this is so, the macros
-_OPT_AUTHENTICATOR_GSASL_SERVER_KEY
-and _HAVE_AUTH_GSASL_SCRAM_S_KEY
-will be defined.
-
-The &$authN$& variables are available when these options are expanded.
-
-If set, the results of expansion should for each
-should be a 28 (for SHA-1) or 44 (for SHA-256) character string
-of base64-coded data, and will be used in preference to the
-&%server_password%& option.
-If unset or not of the right length, &%server_password%& will be used.
-
-The libgsasl library release includes a utility &'gsasl'& which can be used
-to generate these values.
-.wen
-
-
-.option server_service gsasl string &`smtp`&
-This is the SASL service that the server claims to implement.
-Some mechanisms will use this data.
-
-
-.section "&(gsasl)& auth variables" "SECTgsaslauthvar"
-.vindex "&$auth1$&, &$auth2$&, etc"
-These may be set when evaluating specific options, as detailed above.
-They will also be set when evaluating &%server_condition%&.
-
-Unless otherwise stated below, the &(gsasl)& integration will use the following
-meanings for these variables:
-
-.ilist
-.vindex "&$auth1$&"
-&$auth1$&: the &'authentication id'&
-.next
-.vindex "&$auth2$&"
-&$auth2$&: the &'authorization id'&
-.next
-.vindex "&$auth3$&"
-&$auth3$&: the &'realm'&
-.endlist
-
-On a per-mechanism basis:
-
-.ilist
-.cindex "authentication" "EXTERNAL"
-EXTERNAL: only &$auth1$& is set, to the possibly empty &'authorization id'&;
-the &%server_condition%& option must be present.
-.next
-.cindex "authentication" "ANONYMOUS"
-ANONYMOUS: only &$auth1$& is set, to the possibly empty &'anonymous token'&;
-the &%server_condition%& option must be present.
-.next
-.cindex "authentication" "GSSAPI"
-GSSAPI: &$auth1$& will be set to the &'GSSAPI Display Name'&;
-&$auth2$& will be set to the &'authorization id'&,
-the &%server_condition%& option must be present.
-.endlist
-
-An &'anonymous token'& is something passed along as an unauthenticated
-identifier; this is analogous to FTP anonymous authentication passing an
-email address, or software-identifier@, as the "password".
-
-
-An example showing the password having the realm specified in the callback
-and demonstrating a Cyrus SASL to GSASL migration approach is:
-.code
-gsasl_cyrusless_crammd5:
-  driver = gsasl
-  public_name = CRAM-MD5
-  server_realm = imap.example.org
-  server_password = ${lookup{$auth1:$auth3:userPassword}\
-                    dbmjz{/etc/sasldb2}{$value}fail}
-  server_set_id = ${quote:$auth1}
-  server_condition = yes
-.endd
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "The heimdal_gssapi authenticator" "CHAPheimdalgss"
-.scindex IIDheimdalgssauth1 "&(heimdal_gssapi)& authenticator"
-.scindex IIDheimdalgssauth2 "authenticators" "&(heimdal_gssapi)&"
-.cindex "authentication" "GSSAPI"
-.cindex "authentication" "Kerberos"
-The &(heimdal_gssapi)& authenticator provides server integration for the
-Heimdal GSSAPI/Kerberos library, permitting Exim to set a keytab pathname
-reliably.
-
-.option server_hostname heimdal_gssapi string&!! "see below"
-This option selects the hostname that is used, with &%server_service%&,
-for constructing the GSS server name, as a &'GSS_C_NT_HOSTBASED_SERVICE'&
-identifier.  The default value is &`$primary_hostname`&.
-
-.option server_keytab heimdal_gssapi string&!! unset
-If set, then Heimdal will not use the system default keytab (typically
-&_/etc/krb5.keytab_&) but instead the pathname given in this option.
-The value should be a pathname, with no &"file:"& prefix.
-
-.option server_service heimdal_gssapi string&!! "smtp"
-This option specifies the service identifier used, in conjunction with
-&%server_hostname%&, for building the identifier for finding credentials
-from the keytab.
-
-
-.section "&(heimdal_gssapi)& auth variables" "SECTheimdalgssauthvar"
-Beware that these variables will typically include a realm, thus will appear
-to be roughly like an email address already.  The &'authzid'& in &$auth2$& is
-not verified, so a malicious client can set it to anything.
-
-The &$auth1$& field should be safely trustable as a value from the Key
-Distribution Center.  Note that these are not quite email addresses.
-Each identifier is for a role, and so the left-hand-side may include a
-role suffix.  For instance, &"joe/admin@EXAMPLE.ORG"&.
-
-.vindex "&$auth1$&, &$auth2$&, etc"
-.ilist
-.vindex "&$auth1$&"
-&$auth1$&: the &'authentication id'&, set to the GSS Display Name.
-.next
-.vindex "&$auth2$&"
-&$auth2$&: the &'authorization id'&, sent within SASL encapsulation after
-authentication.  If that was empty, this will also be set to the
-GSS Display Name.
-.endlist
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "The spa authenticator" "CHAPspa"
-.scindex IIDspaauth1 "&(spa)& authenticator"
-.scindex IIDspaauth2 "authenticators" "&(spa)&"
-.cindex "authentication" "Microsoft Secure Password"
-.cindex "authentication" "NTLM"
-.cindex "Microsoft Secure Password Authentication"
-.cindex "NTLM authentication"
-The &(spa)& authenticator provides client support for Microsoft's &'Secure
-Password Authentication'& mechanism,
-which is also sometimes known as NTLM (NT LanMan). The code for client side of
-this authenticator was contributed by Marc Prud'hommeaux, and much of it is
-taken from the Samba project (&url(https://www.samba.org/)). The code for the
-server side was subsequently contributed by Tom Kistner. The mechanism works as
-follows:
-
-.ilist
-After the AUTH command has been accepted, the client sends an SPA
-authentication request based on the user name and optional domain.
-.next
-The server sends back a challenge.
-.next
-The client builds a challenge response which makes use of the user's password
-and sends it to the server, which then accepts or rejects it.
-.endlist
-
-Encryption is used to protect the password in transit.
-
-
-
-.section "Using spa as a server" "SECID179"
-.cindex "options" "&(spa)& authenticator (server)"
-The &(spa)& authenticator has just one server option:
-
-.option server_password spa string&!! unset
-.cindex "numerical variables (&$1$& &$2$& etc)" "in &(spa)& authenticator"
-This option is expanded, and the result must be the cleartext password for the
-authenticating user, whose name is at this point in &$auth1$&. For
-compatibility with previous releases of Exim, the user name is also placed in
-&$1$&. However, the use of this variable for this purpose is now deprecated, as
-it can lead to confusion in string expansions that also use numeric variables
-for other things. For example:
-.code
-spa:
-  driver = spa
-  public_name = NTLM
-  server_password = \
-    ${lookup{$auth1}lsearch{/etc/exim/spa_clearpass}{$value}fail}
-.endd
-If the expansion is forced to fail, authentication fails. Any other expansion
-failure causes a temporary error code to be returned.
-
-
-
-
-
-.section "Using spa as a client" "SECID180"
-.cindex "options" "&(spa)& authenticator (client)"
-The &(spa)& authenticator has the following client options:
-
-
-
-.option client_domain spa string&!! unset
-This option specifies an optional domain for the authentication.
-
-
-.option client_password spa string&!! unset
-This option specifies the user's password, and must be set.
-
-
-.option client_username spa string&!! unset
-This option specifies the user name, and must be set. Here is an example of a
-configuration of this authenticator for use with the mail servers at
-&'msn.com'&:
-.code
-msn:
-  driver = spa
-  public_name = MSN
-  client_username = msn/msn_username
-  client_password = msn_plaintext_password
-  client_domain = DOMAIN_OR_UNSET
-.endd
-.ecindex IIDspaauth1
-.ecindex IIDspaauth2
-
-
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "The external authenticator" "CHAPexternauth"
-.scindex IIDexternauth1 "&(external)& authenticator"
-.scindex IIDexternauth2 "authenticators" "&(external)&"
-.cindex "authentication" "Client Certificate"
-.cindex "authentication" "X509"
-.cindex "Certificate-based authentication"
-The &(external)& authenticator provides support for
-authentication based on non-SMTP information.
-The specification is in RFC 4422 Appendix A
-(&url(https://tools.ietf.org/html/rfc4422)).
-It is only a transport and negotiation mechanism;
-the process of authentication is entirely controlled
-by the server configuration.
-
-The client presents an identity in-clear.
-It is probably wise for a server to only advertise,
-and for clients to only attempt,
-this authentication method on a secure (eg. under TLS) connection.
-
-One possible use, compatible with the
-K-9 Mail Andoid client (&url(https://k9mail.github.io/)),
-is for using X509 client certificates.
-
-It thus overlaps in function with the TLS authenticator
-(see &<<CHAPtlsauth>>&)
-but is a full SMTP SASL authenticator
-rather than being implicit for TLS-connection carried
-client certificates only.
-
-The examples and discussion in this chapter assume that
-client-certificate authentication is being done.
-
-The client must present a certificate,
-for which it must have been requested via the
-&%tls_verify_hosts%& or &%tls_try_verify_hosts%& main options
-(see &<<CHAPTLS>>&).
-For authentication to be effective the certificate should be
-verifiable against a trust-anchor certificate known to the server.
-
-.section "External options" "SECTexternsoptions"
-.cindex "options" "&(external)& authenticator (server)"
-The &(external)& authenticator has two server options:
-
-.option server_param2 external string&!! unset
-.option server_param3 external string&!! unset
-.cindex "variables (&$auth1$& &$auth2$& etc)" "in &(external)& authenticator"
-These options are expanded before the &%server_condition%& option
-and the result are placed in &$auth2$& and &$auth3$& resectively.
-If the expansion is forced to fail, authentication fails. Any other expansion
-failure causes a temporary error code to be returned.
-
-They can be used to clarify the coding of a complex &%server_condition%&.
-
-.section "Using external in a server" "SECTexternserver"
-.cindex "AUTH" "in &(external)& authenticator"
-.cindex "numerical variables (&$1$& &$2$& etc)" &&&
-        "in &(external)& authenticator"
-.vindex "&$auth1$&, &$auth2$&, etc"
-.cindex "base64 encoding" "in &(external)& authenticator"
-
-When running as a server, &(external)& performs the authentication test by
-expanding a string. The data sent by the client with the AUTH command, or in
-response to subsequent prompts, is base64 encoded, and so may contain any byte
-values when decoded. The decoded value is treated as
-an identity for authentication and
-placed in the expansion variable &$auth1$&.
-
-For compatibility with previous releases of Exim, the value is also placed in
-the expansion variable &$1$&. However, the use of this
-variable for this purpose is now deprecated, as it can lead to confusion in
-string expansions that also use them for other things.
-
-.vindex "&$authenticated_id$&"
-Once an identity has been received,
-&%server_condition%& is expanded. If the expansion is forced to fail,
-authentication fails. Any other expansion failure causes a temporary error code
-to be returned. If the result of a successful expansion is an empty string,
-&"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
-expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
-generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
-For any other result, a temporary error code is returned, with the expanded
-string as the error text.
-
-Example:
-.code
-ext_ccert_san_mail:
-  driver =            external
-  public_name =       EXTERNAL
-
-  server_advertise_condition = $tls_in_certificate_verified
-  server_param2 =     ${certextract {subj_altname,mail,>:} \
-                                    {$tls_in_peercert}}
-  server_condition =  ${if forany {$auth2} \
-                            {eq {$item}{$auth1}}}
-  server_set_id =     $auth1
-.endd
-This accepts a client certificate that is verifiable against any
-of your configured trust-anchors
-(which usually means the full set of public CAs)
-and which has a mail-SAN matching the claimed identity sent by the client.
-
-&*Note*&: up to TLS1.2, the client cert is on the wire in-clear, including the SAN.
-The account name is therefore guessable by an opponent.
-TLS 1.3 protects both server and client certificates, and is not vulnerable
-in this way.
-
-
-.section "Using external in a client" "SECTexternclient"
-.cindex "options" "&(external)& authenticator (client)"
-The &(external)& authenticator has one client option:
-
-.option client_send external string&!! unset
-This option is expanded and sent with the AUTH command as the
-identity being asserted.
-
-Example:
-.code
-ext_ccert:
-  driver =      external
-  public_name = EXTERNAL
-
-  client_condition = ${if !eq{$tls_out_cipher}{}}
-  client_send = myaccount@smarthost.example.net
-.endd
-
-
-.ecindex IIDexternauth1
-.ecindex IIDexternauth2
-
-
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "The tls authenticator" "CHAPtlsauth"
-.scindex IIDtlsauth1 "&(tls)& authenticator"
-.scindex IIDtlsauth2 "authenticators" "&(tls)&"
-.cindex "authentication" "Client Certificate"
-.cindex "authentication" "X509"
-.cindex "Certificate-based authentication"
-The &(tls)& authenticator provides server support for
-authentication based on client certificates.
-
-It is not an SMTP authentication mechanism and is not
-advertised by the server as part of the SMTP EHLO response.
-It is an Exim authenticator in the sense that it affects
-the protocol element of the log line, can be tested for
-by the &%authenticated%& ACL condition, and can set
-the &$authenticated_id$& variable.
-
-The client must present a verifiable certificate,
-for which it must have been requested via the
-&%tls_verify_hosts%& or &%tls_try_verify_hosts%& main options
-(see &<<CHAPTLS>>&).
-
-If an authenticator of this type is configured it is
-run before any SMTP-level communication is done,
-and can authenticate the connection.
-If it does, SMTP authentication is not offered.
-
-A maximum of one authenticator of this type may be present.
-
-
-.cindex "options" "&(tls)& authenticator (server)"
-The &(tls)& authenticator has three server options:
-
-.option server_param1 tls string&!! unset
-.cindex "variables (&$auth1$& &$auth2$& etc)" "in &(tls)& authenticator"
-This option is expanded after the TLS negotiation and
-the result is placed in &$auth1$&.
-If the expansion is forced to fail, authentication fails. Any other expansion
-failure causes a temporary error code to be returned.
-
-.option server_param2 tls string&!! unset
-.option server_param3 tls string&!! unset
-As above, for &$auth2$& and &$auth3$&.
-
-&%server_param1%& may also be spelled &%server_param%&.
-
-
-Example:
-.code
-tls:
-  driver = tls
-  server_param1 =     ${certextract {subj_altname,mail,>:} \
-                                    {$tls_in_peercert}}
-  server_condition =  ${if and { {eq{$tls_in_certificate_verified}{1}} \
-                                 {forany {$auth1} \
-                            {!= {0} \
-                                {${lookup ldap{ldap:///\
-                         mailname=${quote_ldap_dn:${lc:$item}},\
-                         ou=users,LDAP_DC?mailid} {$value}{0} \
-                       }    }  } }}}
-  server_set_id =     ${if = {1}{${listcount:$auth1}} {$auth1}{}}
-.endd
-This accepts a client certificate that is verifiable against any
-of your configured trust-anchors
-(which usually means the full set of public CAs)
-and which has a SAN with a good account name.
-
-Note that, up to TLS1.2, the client cert is on the wire in-clear, including the SAN,
-The account name is therefore guessable by an opponent.
-TLS 1.3 protects both server and client certificates, and is not vulnerable
-in this way.
-Likewise, a traditional plaintext SMTP AUTH done inside TLS is not.
-
-. An alternative might use
-. .code
-.   server_param1 = ${sha256:$tls_in_peercert}
-. .endd
-. to require one of a set of specific certs that define a given account
-. (the verification is still required, but mostly irrelevant).
-. This would help for per-device use.
-.
-. However, for the future we really need support for checking a
-. user cert in LDAP - which probably wants a base-64 DER.
-
-.ecindex IIDtlsauth1
-.ecindex IIDtlsauth2
-
-
-Note that because authentication is traditionally an SMTP operation,
-the &%authenticated%& ACL condition cannot be used in
-a connect- or helo-ACL.
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "Encrypted SMTP connections using TLS/SSL" "CHAPTLS" &&&
-         "Encrypted SMTP connections"
-.scindex IIDencsmtp1 "encryption" "on SMTP connection"
-.scindex IIDencsmtp2 "SMTP" "encryption"
-.cindex "TLS" "on SMTP connection"
-.cindex "OpenSSL"
-.cindex "GnuTLS"
-Support for TLS (Transport Layer Security), formerly known as SSL (Secure
-Sockets Layer), is implemented by making use of the OpenSSL library or the
-GnuTLS library (Exim requires GnuTLS release 1.0 or later). There is no
-cryptographic code in the Exim distribution itself for implementing TLS. In
-order to use this feature you must install OpenSSL or GnuTLS, and then build a
-version of Exim that includes TLS support (see section &<<SECTinctlsssl>>&).
-You also need to understand the basic concepts of encryption at a managerial
-level, and in particular, the way that public keys, private keys, and
-certificates are used.
-
-RFC 3207 defines how SMTP connections can make use of encryption. Once a
-connection is established, the client issues a STARTTLS command. If the
-server accepts this, the client and the server negotiate an encryption
-mechanism. If the negotiation succeeds, the data that subsequently passes
-between them is encrypted.
-
-Exim's ACLs can detect whether the current SMTP session is encrypted or not,
-and if so, what cipher suite is in use, whether the client supplied a
-certificate, and whether or not that certificate was verified. This makes it
-possible for an Exim server to deny or accept certain commands based on the
-encryption state.
-
-&*Warning*&: Certain types of firewall and certain anti-virus products can
-disrupt TLS connections. You need to turn off SMTP scanning for these products
-in order to get TLS to work.
-
-
-
-.section "Support for the &""submissions""& (aka &""ssmtp""& and &""smtps""&) protocol" &&&
-         "SECID284"
-.cindex "submissions protocol"
-.cindex "ssmtp protocol"
-.cindex "smtps protocol"
-.cindex "SMTP" "submissions protocol"
-.cindex "SMTP" "ssmtp protocol"
-.cindex "SMTP" "smtps protocol"
-The history of port numbers for TLS in SMTP is a little messy and has been
-contentious.  As of RFC 8314, the common practice of using the historically
-allocated port 465 for "email submission but with TLS immediately upon connect
-instead of using STARTTLS" is officially blessed by the IETF, and recommended
-by them in preference to STARTTLS.
-
-The name originally assigned to the port was &"ssmtp"& or &"smtps"&, but as
-clarity emerged over the dual roles of SMTP, for MX delivery and Email
-Submission, nomenclature has shifted.  The modern name is now &"submissions"&.
-
-This approach was, for a while, officially abandoned when encrypted SMTP was
-standardized, but many clients kept using it, even as the TCP port number was
-reassigned for other use.
-Thus you may encounter guidance claiming that you shouldn't enable use of
-this port.
-In practice, a number of mail-clients have only ever supported submissions,
-not submission with STARTTLS upgrade.
-Ideally, offer both submission (587) and submissions (465) service.
-
-Exim supports TLS-on-connect by means of the &%tls_on_connect_ports%&
-global option. Its value must be a list of port numbers;
-the most common use is expected to be:
-.code
-tls_on_connect_ports = 465
-.endd
-The port numbers specified by this option apply to all SMTP connections, both
-via the daemon and via &'inetd'&. You still need to specify all the ports that
-the daemon uses (by setting &%daemon_smtp_ports%& or &%local_interfaces%& or
-the &%-oX%& command line option) because &%tls_on_connect_ports%& does not add
-an extra port &-- rather, it specifies different behaviour on a port that is
-defined elsewhere.
-
-There is also a &%-tls-on-connect%& command line option. This overrides
-&%tls_on_connect_ports%&; it forces the TLS-only behaviour for all ports.
-
-
-
-
-
-
-.section "OpenSSL vs GnuTLS" "SECTopenvsgnu"
-.cindex "TLS" "OpenSSL &'vs'& GnuTLS"
-TLS is supported in Exim using either the OpenSSL or GnuTLS library.
-To build Exim to use OpenSSL you need to set
-.code
-USE_OPENSSL=yes
-.endd
-in Local/Makefile.
-
-To build Exim to use GnuTLS, you need to set
-.code
-USE_GNUTLS=yes
-.endd
-in Local/Makefile.
-
-You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the
-include files and libraries for GnuTLS can be found.
-
-There are some differences in usage when using GnuTLS instead of OpenSSL:
-
-.ilist
-The &%tls_verify_certificates%& option
-cannot be the path of a directory
-for GnuTLS versions before 3.3.6
-(for later versions, or OpenSSL, it can be either).
-.next
-The default value for &%tls_dhparam%& differs for historical reasons.
-.next
-.vindex "&$tls_in_peerdn$&"
-.vindex "&$tls_out_peerdn$&"
-Distinguished Name (DN) strings reported by the OpenSSL library use a slash for
-separating fields; GnuTLS uses commas, in accordance with RFC 2253. This
-affects the value of the &$tls_in_peerdn$& and &$tls_out_peerdn$& variables.
-.next
-OpenSSL identifies cipher suites using hyphens as separators, for example:
-DES-CBC3-SHA. GnuTLS historically used underscores, for example:
-RSA_ARCFOUR_SHA. What is more, OpenSSL complains if underscores are present
-in a cipher list. To make life simpler, Exim changes underscores to hyphens
-for OpenSSL and passes the string unchanged to GnuTLS (expecting the library
-to handle its own older variants) when processing lists of cipher suites in the
-&%tls_require_ciphers%& options (the global option and the &(smtp)& transport
-option).
-.next
-The &%tls_require_ciphers%& options operate differently, as described in the
-sections &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
-.next
-The &%tls_dh_min_bits%& SMTP transport option is only honoured by GnuTLS.
-When using OpenSSL, this option is ignored.
-(If an API is found to let OpenSSL be configured in this way,
-let the Exim Maintainers know and we'll likely use it).
-.next
-With GnuTLS, if an explicit list is used for the &%tls_privatekey%& main option
-main option, it must be ordered to match the &%tls_certificate%& list.
-.next
-Some other recently added features may only be available in one or the other.
-This should be documented with the feature.  If the documentation does not
-explicitly state that the feature is infeasible in the other TLS
-implementation, then patches are welcome.
-.endlist
-
-
-.section "GnuTLS parameter computation" "SECTgnutlsparam"
-This section only applies if &%tls_dhparam%& is set to &`historic`& or to
-an explicit path; if the latter, then the text about generation still applies,
-but not the chosen filename.
-By default, as of Exim 4.80 a hard-coded D-H prime is used.
-See the documentation of &%tls_dhparam%& for more information.
-
-GnuTLS uses D-H parameters that may take a substantial amount of time
-to compute. It is unreasonable to re-compute them for every TLS session.
-Therefore, Exim keeps this data in a file in its spool directory, called
-&_gnutls-params-NNNN_& for some value of NNNN, corresponding to the number
-of bits requested.
-The file is owned by the Exim user and is readable only by
-its owner. Every Exim process that start up GnuTLS reads the D-H
-parameters from this file. If the file does not exist, the first Exim process
-that needs it computes the data and writes it to a temporary file which is
-renamed once it is complete. It does not matter if several Exim processes do
-this simultaneously (apart from wasting a few resources). Once a file is in
-place, new Exim processes immediately start using it.
-
-For maximum security, the parameters that are stored in this file should be
-recalculated periodically, the frequency depending on your paranoia level.
-If you are avoiding using the fixed D-H primes published in RFCs, then you
-are concerned about some advanced attacks and will wish to do this; if you do
-not regenerate then you might as well stick to the standard primes.
-
-Arranging this is easy in principle; just delete the file when you want new
-values to be computed. However, there may be a problem. The calculation of new
-parameters needs random numbers, and these are obtained from &_/dev/random_&.
-If the system is not very active, &_/dev/random_& may delay returning data
-until enough randomness (entropy) is available. This may cause Exim to hang for
-a substantial amount of time, causing timeouts on incoming connections.
-
-The solution is to generate the parameters externally to Exim. They are stored
-in &_gnutls-params-N_& in PEM format, which means that they can be
-generated externally using the &(certtool)& command that is part of GnuTLS.
-
-To replace the parameters with new ones, instead of deleting the file
-and letting Exim re-create it, you can generate new parameters using
-&(certtool)& and, when this has been done, replace Exim's cache file by
-renaming. The relevant commands are something like this:
-.code
-# ls
-[ look for file; assume gnutls-params-2236 is the most recent ]
-# rm -f new-params
-# touch new-params
-# chown exim:exim new-params
-# chmod 0600 new-params
-# certtool --generate-dh-params --bits 2236 >>new-params
-# openssl dhparam -noout -text -in new-params | head
-[ check the first line, make sure it's not more than 2236;
-  if it is, then go back to the start ("rm") and repeat
-  until the size generated is at most the size requested ]
-# chmod 0400 new-params
-# mv new-params gnutls-params-2236
-.endd
-If Exim never has to generate the parameters itself, the possibility of
-stalling is removed.
-
-The filename changed in Exim 4.80, to gain the -bits suffix.  The value which
-Exim will choose depends upon the version of GnuTLS in use.  For older GnuTLS,
-the value remains hard-coded in Exim as 1024.  As of GnuTLS 2.12.x, there is
-a way for Exim to ask for the "normal" number of bits for D-H public-key usage,
-and Exim does so.  This attempt to remove Exim from TLS policy decisions
-failed, as GnuTLS 2.12 returns a value higher than the current hard-coded limit
-of the NSS library.  Thus Exim gains the &%tls_dh_max_bits%& global option,
-which applies to all D-H usage, client or server.  If the value returned by
-GnuTLS is greater than &%tls_dh_max_bits%& then the value will be clamped down
-to &%tls_dh_max_bits%&.  The default value has been set at the current NSS
-limit, which is still much higher than Exim historically used.
-
-The filename and bits used will change as the GnuTLS maintainers change the
-value for their parameter &`GNUTLS_SEC_PARAM_NORMAL`&, as clamped by
-&%tls_dh_max_bits%&.  At the time of writing (mid 2012), GnuTLS 2.12 recommends
-2432 bits, while NSS is limited to 2236 bits.
-
-In fact, the requested value will be *lower* than &%tls_dh_max_bits%&, to
-increase the chance of the generated prime actually being within acceptable
-bounds, as GnuTLS has been observed to overshoot.  Note the check step in the
-procedure above.  There is no sane procedure available to Exim to double-check
-the size of the generated prime, so it might still be too large.
-
-
-.section "Requiring specific ciphers in OpenSSL" "SECTreqciphssl"
-.cindex "TLS" "requiring specific ciphers (OpenSSL)"
-.oindex "&%tls_require_ciphers%&" "OpenSSL"
-There is a function in the OpenSSL library that can be passed a list of cipher
-suites before the cipher negotiation takes place. This specifies which ciphers
-are acceptable for TLS versions prior to 1.3.
-The list is colon separated and may contain names like
-DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%&
-directly to this function call.
-Many systems will install the OpenSSL manual-pages, so you may have
-&'ciphers(1)'& available to you.
-The following quotation from the OpenSSL
-documentation specifies what forms of item are allowed in the cipher string:
-
-.ilist
-It can consist of a single cipher suite such as RC4-SHA.
-.next
-It can represent a list of cipher suites containing a certain algorithm,
-or cipher suites of a certain type. For example SHA1 represents all
-ciphers suites using the digest algorithm SHA1 and SSLv3 represents all
-SSL v3 algorithms.
-.next
-Lists of cipher suites can be combined in a single cipher string using
-the + character. This is used as a logical and operation. For example
-SHA1+DES represents all cipher suites containing the SHA1 and the DES
-algorithms.
-.endlist
-
-Each cipher string can be optionally preceded by one of the characters &`!`&,
-&`-`& or &`+`&.
-.ilist
-If &`!`& is used, the ciphers are permanently deleted from the list. The
-ciphers deleted can never reappear in the list even if they are explicitly
-stated.
-.next
-If &`-`& is used, the ciphers are deleted from the list, but some or all
-of the ciphers can be added again by later options.
-.next
-If &`+`& is used, the ciphers are moved to the end of the list. This
-option does not add any new ciphers; it just moves matching existing ones.
-.endlist
-
-If none of these characters is present, the string is interpreted as
-a list of ciphers to be appended to the current preference list. If the list
-includes any ciphers already present they will be ignored: that is, they will
-not be moved to the end of the list.
-.endlist
-
-The OpenSSL &'ciphers(1)'& command may be used to test the results of a given
-string:
-.code
-# note single-quotes to get ! past any shell history expansion
-$ openssl ciphers 'HIGH:!MD5:!SHA1'
-.endd
-
-This example will let the library defaults be permitted on the MX port, where
-there's probably no identity verification anyway, but ups the ante on the
-submission ports where the administrator might have some influence on the
-choice of clients used:
-.code
-# OpenSSL variant; see man ciphers(1)
-tls_require_ciphers = ${if =={$received_port}{25}\
-                           {DEFAULT}\
-                           {HIGH:!MD5:!SHA1}}
-.endd
-
-This example will prefer ECDSA-authenticated ciphers over RSA ones:
-.code
-tls_require_ciphers = ECDSA:RSA:!COMPLEMENTOFDEFAULT
-.endd
-
-For TLS version 1.3 the control available is less fine-grained
-and Exim does not provide access to it at present.
-The value of the &%tls_require_ciphers%& option is ignored when
-TLS version 1.3 is negotiated.
-
-As of writing the library default cipher suite list for TLSv1.3 is
-.code
-TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256
-.endd
-
-
-.section "Requiring specific ciphers or other parameters in GnuTLS" &&&
-         "SECTreqciphgnu"
-.cindex "GnuTLS" "specifying parameters for"
-.cindex "TLS" "specifying ciphers (GnuTLS)"
-.cindex "TLS" "specifying key exchange methods (GnuTLS)"
-.cindex "TLS" "specifying MAC algorithms (GnuTLS)"
-.cindex "TLS" "specifying protocols (GnuTLS)"
-.cindex "TLS" "specifying priority string (GnuTLS)"
-.oindex "&%tls_require_ciphers%&" "GnuTLS"
-The GnuTLS library allows the caller to provide a "priority string", documented
-as part of the &[gnutls_priority_init]& function.  This is very similar to the
-ciphersuite specification in OpenSSL.
-
-The &%tls_require_ciphers%& option is treated as the GnuTLS priority string
-and controls both protocols and ciphers.
-
-The &%tls_require_ciphers%& option is available both as an global option,
-controlling how Exim behaves as a server, and also as an option of the
-&(smtp)& transport, controlling how Exim behaves as a client.  In both cases
-the value is string expanded.  The resulting string is not an Exim list and
-the string is given to the GnuTLS library, so that Exim does not need to be
-aware of future feature enhancements of GnuTLS.
-
-Documentation of the strings accepted may be found in the GnuTLS manual, under
-"Priority strings".  This is online as
-&url(https://www.gnutls.org/manual/html_node/Priority-Strings.html),
-but beware that this relates to GnuTLS 3, which may be newer than the version
-installed on your system.  If you are using GnuTLS 3,
-then the example code
-&url(https://www.gnutls.org/manual/gnutls.html#Listing-the-ciphersuites-in-a-priority-string)
-on that site can be used to test a given string.
-
-For example:
-.code
-# Disable older versions of protocols
-tls_require_ciphers = NORMAL:%LATEST_RECORD_VERSION:-VERS-SSL3.0
-.endd
-
-Prior to Exim 4.80, an older API of GnuTLS was used, and Exim supported three
-additional options, "&%gnutls_require_kx%&", "&%gnutls_require_mac%&" and
-"&%gnutls_require_protocols%&".  &%tls_require_ciphers%& was an Exim list.
-
-This example will let the library defaults be permitted on the MX port, where
-there's probably no identity verification anyway, and lowers security further
-by increasing compatibility; but this ups the ante on the submission ports
-where the administrator might have some influence on the choice of clients
-used:
-.code
-# GnuTLS variant
-tls_require_ciphers = ${if =={$received_port}{25}\
-                           {NORMAL:%COMPAT}\
-                           {SECURE128}}
-.endd
-
-
-.section "Configuring an Exim server to use TLS" "SECID182"
-.cindex "TLS" "configuring an Exim server"
-When Exim has been built with TLS support, it advertises the availability of
-the STARTTLS command to client hosts that match &%tls_advertise_hosts%&,
-but not to any others. The default value of this option is *, which means
-that STARTTLS is always advertised.  Set it to blank to never advertise;
-this is reasonable for systems that want to use TLS only as a client.
-
-If STARTTLS is to be used you
-need to set some other options in order to make TLS available.
-
-If a client issues a STARTTLS command and there is some configuration
-problem in the server, the command is rejected with a 454 error. If the client
-persists in trying to issue SMTP commands, all except QUIT are rejected
-with the error
-.code
-554 Security failure
-.endd
-If a STARTTLS command is issued within an existing TLS session, it is
-rejected with a 554 error code.
-
-To enable TLS operations on a server, the &%tls_advertise_hosts%& option
-must be set to match some hosts. The default is * which matches all hosts.
-
-If this is all you do, TLS encryption will be enabled but not authentication -
-meaning that the peer has no assurance it is actually you he is talking to.
-You gain protection from a passive sniffer listening on the wire but not
-from someone able to intercept the communication.
-
-Further protection requires some further configuration at the server end.
-
-To make TLS work you need to set, in the server,
-.code
-tls_certificate = /some/file/name
-tls_privatekey = /some/file/name
-.endd
-These options are, in fact, expanded strings, so you can make them depend on
-the identity of the client that is connected if you wish. The first file
-contains the server's X509 certificate, and the second contains the private key
-that goes with it. These files need to be
-PEM format and readable by the Exim user, and must
-always be given as full path names.
-The key must not be password-protected.
-They can be the same file if both the
-certificate and the key are contained within it. If &%tls_privatekey%& is not
-set, or if its expansion is forced to fail or results in an empty string, this
-is assumed to be the case. The certificate file may also contain intermediate
-certificates that need to be sent to the client to enable it to authenticate
-the server's certificate.
-
-For dual-stack (eg. RSA and ECDSA) configurations, these options can be
-colon-separated lists of file paths.  Ciphers using given authentication
-algorithms require the presence of a suitable certificate to supply the
-public-key.  The server selects among the certificates to present to the
-client depending on the selected cipher, hence the priority ordering for
-ciphers will affect which certificate is used.
-
-If you do not understand about certificates and keys, please try to find a
-source of this background information, which is not Exim-specific. (There are a
-few comments below in section &<<SECTcerandall>>&.)
-
-&*Note*&: These options do not apply when Exim is operating as a client &--
-they apply only in the case of a server. If you need to use a certificate in an
-Exim client, you must set the options of the same names in an &(smtp)&
-transport.
-
-With just these options, an Exim server will be able to use TLS. It does not
-require the client to have a certificate (but see below for how to insist on
-this). There is one other option that may be needed in other situations. If
-.code
-tls_dhparam = /some/file/name
-.endd
-is set, the SSL library is initialized for the use of Diffie-Hellman ciphers
-with the parameters contained in the file.
-Set this to &`none`& to disable use of DH entirely, by making no prime
-available:
-.code
-tls_dhparam = none
-.endd
-This may also be set to a string identifying a standard prime to be used for
-DH; if it is set to &`default`& or, for OpenSSL, is unset, then the prime
-used is &`ike23`&.  There are a few standard primes available, see the
-documentation for &%tls_dhparam%& for the complete list.
-
-See the command
-.code
-openssl dhparam
-.endd
-for a way of generating file data.
-
-The strings supplied for these three options are expanded every time a client
-host connects. It is therefore possible to use different certificates and keys
-for different hosts, if you so wish, by making use of the client's IP address
-in &$sender_host_address$& to control the expansion. If a string expansion is
-forced to fail, Exim behaves as if the option is not set.
-
-.cindex "cipher" "logging"
-.cindex "log" "TLS cipher"
-.vindex "&$tls_in_cipher$&"
-The variable &$tls_in_cipher$& is set to the cipher suite that was negotiated for
-an incoming TLS connection. It is included in the &'Received:'& header of an
-incoming message (by default &-- you can, of course, change this), and it is
-also included in the log line that records a message's arrival, keyed by
-&"X="&, unless the &%tls_cipher%& log selector is turned off. The &%encrypted%&
-condition can be used to test for specific cipher suites in ACLs.
-
-Once TLS has been established, the ACLs that run for subsequent SMTP commands
-can check the name of the cipher suite and vary their actions accordingly. The
-cipher suite names vary, depending on which TLS library is being used. For
-example, OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other
-contexts is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL or GnuTLS
-documentation for more details.
-
-For outgoing SMTP deliveries, &$tls_out_cipher$& is used and logged
-(again depending on the &%tls_cipher%& log selector).
-
-
-.section "Requesting and verifying client certificates" "SECID183"
-.cindex "certificate" "verification of client"
-.cindex "TLS" "client certificate verification"
-If you want an Exim server to request a certificate when negotiating a TLS
-session with a client, you must set either &%tls_verify_hosts%& or
-&%tls_try_verify_hosts%&. You can, of course, set either of them to * to
-apply to all TLS connections. For any host that matches one of these options,
-Exim requests a certificate as part of the setup of the TLS session. The
-contents of the certificate are verified by comparing it with a list of
-expected trust-anchors or certificates.
-These may be the system default set (depending on library version),
-an explicit file or,
-depending on library version, a directory, identified by
-&%tls_verify_certificates%&.
-
-A file can contain multiple certificates, concatenated end to end. If a
-directory is used
-(OpenSSL only),
-each certificate must be in a separate file, with a name (or a symbolic link)
-of the form <&'hash'&>.0, where <&'hash'&> is a hash value constructed from the
-certificate. You can compute the relevant hash by running the command
-.code
-openssl x509 -hash -noout -in /cert/file
-.endd
-where &_/cert/file_& contains a single certificate.
-
-There is no checking of names of the client against the certificate
-Subject Name or Subject Alternate Names.
-
-The difference between &%tls_verify_hosts%& and &%tls_try_verify_hosts%& is
-what happens if the client does not supply a certificate, or if the certificate
-does not match any of the certificates in the collection named by
-&%tls_verify_certificates%&. If the client matches &%tls_verify_hosts%&, the
-attempt to set up a TLS session is aborted, and the incoming connection is
-dropped. If the client matches &%tls_try_verify_hosts%&, the (encrypted) SMTP
-session continues. ACLs that run for subsequent SMTP commands can detect the
-fact that no certificate was verified, and vary their actions accordingly. For
-example, you can insist on a certificate before accepting a message for
-relaying, but not when the message is destined for local delivery.
-
-.vindex "&$tls_in_peerdn$&"
-When a client supplies a certificate (whether it verifies or not), the value of
-the Distinguished Name of the certificate is made available in the variable
-&$tls_in_peerdn$& during subsequent processing of the message.
-
-.cindex "log" "distinguished name"
-Because it is often a long text string, it is not included in the log line or
-&'Received:'& header by default. You can arrange for it to be logged, keyed by
-&"DN="&, by setting the &%tls_peerdn%& log selector, and you can use
-&%received_header_text%& to change the &'Received:'& header. When no
-certificate is supplied, &$tls_in_peerdn$& is empty.
-
-
-.section "Revoked certificates" "SECID184"
-.cindex "TLS" "revoked certificates"
-.cindex "revocation list"
-.cindex "certificate" "revocation list"
-.cindex "OCSP" "stapling"
-Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when
-certificates are revoked. If you have such a list, you can pass it to an Exim
-server using the global option called &%tls_crl%& and to an Exim client using
-an identically named option for the &(smtp)& transport. In each case, the value
-of the option is expanded and must then be the name of a file that contains a
-CRL in PEM format.
-The downside is that clients have to periodically re-download a potentially huge
-file from every certificate authority they know of.
-
-The way with most moving parts at query time is Online Certificate
-Status Protocol (OCSP), where the client verifies the certificate
-against an OCSP server run by the CA.  This lets the CA track all
-usage of the certs.  It requires running software with access to the
-private key of the CA, to sign the responses to the OCSP queries.  OCSP
-is based on HTTP and can be proxied accordingly.
-
-The only widespread OCSP server implementation (known to this writer)
-comes as part of OpenSSL and aborts on an invalid request, such as
-connecting to the port and then disconnecting.  This requires
-re-entering the passphrase each time some random client does this.
-
-The third way is OCSP Stapling; in this, the server using a certificate
-issued by the CA periodically requests an OCSP proof of validity from
-the OCSP server, then serves it up inline as part of the TLS
-negotiation.   This approach adds no extra round trips, does not let the
-CA track users, scales well with number of certs issued by the CA and is
-resilient to temporary OCSP server failures, as long as the server
-starts retrying to fetch an OCSP proof some time before its current
-proof expires.  The downside is that it requires server support.
-
-Unless Exim is built with the support disabled,
-or with GnuTLS earlier than version 3.3.16 / 3.4.8
-support for OCSP stapling is included.
-
-There is a global option called &%tls_ocsp_file%&.
-The file specified therein is expected to be in DER format, and contain
-an OCSP proof.  Exim will serve it as part of the TLS handshake.  This
-option will be re-expanded for SNI, if the &%tls_certificate%& option
-contains &`tls_in_sni`&, as per other TLS options.
-
-Exim does not at this time implement any support for fetching a new OCSP
-proof.  The burden is on the administrator to handle this, outside of
-Exim.  The file specified should be replaced atomically, so that the
-contents are always valid.  Exim will expand the &%tls_ocsp_file%& option
-on each connection, so a new file will be handled transparently on the
-next connection.
-
-When built with OpenSSL Exim will check for a valid next update timestamp
-in the OCSP proof; if not present, or if the proof has expired, it will be
-ignored.
-
-For the client to be able to verify the stapled OCSP the server must
-also supply, in its stapled information, any intermediate
-certificates for the chain leading to the OCSP proof from the signer
-of the server certificate.  There may be zero or one such. These
-intermediate certificates should be added to the server OCSP stapling
-file named by &%tls_ocsp_file%&.
-
-Note that the proof only covers the terminal server certificate,
-not any of the chain from CA to it.
-
-There is no current way to staple a proof for a client certificate.
-
-.code
-  A helper script "ocsp_fetch.pl" for fetching a proof from a CA
-  OCSP server is supplied.  The server URL may be included in the
-  server certificate, if the CA is helpful.
-
-  One failure mode seen was the OCSP Signer cert expiring before the end
-  of validity of the OCSP proof. The checking done by Exim/OpenSSL
-  noted this as invalid overall, but the re-fetch script did not.
-.endd
-
-
-
-
-.section "Configuring an Exim client to use TLS" "SECTclientTLS"
-.cindex "cipher" "logging"
-.cindex "log" "TLS cipher"
-.cindex "log" "distinguished name"
-.cindex "TLS" "configuring an Exim client"
-The &%tls_cipher%& and &%tls_peerdn%& log selectors apply to outgoing SMTP
-deliveries as well as to incoming, the latter one causing logging of the
-server certificate's DN. The remaining client configuration for TLS is all
-within the &(smtp)& transport.
-
-It is not necessary to set any options to have TLS work in the &(smtp)&
-transport. If Exim is built with TLS support, and TLS is advertised by a
-server, the &(smtp)& transport always tries to start a TLS session. However,
-this can be prevented by setting &%hosts_avoid_tls%& (an option of the
-transport) to a list of server hosts for which TLS should not be used.
-
-If you do not want Exim to attempt to send messages unencrypted when an attempt
-to set up an encrypted connection fails in any way, you can set
-&%hosts_require_tls%& to a list of hosts for which encryption is mandatory. For
-those hosts, delivery is always deferred if an encrypted connection cannot be
-set up. If there are any other hosts for the address, they are tried in the
-usual way.
-
-When the server host is not in &%hosts_require_tls%&, Exim may try to deliver
-the message unencrypted. It always does this if the response to STARTTLS is
-a 5&'xx'& code. For a temporary error code, or for a failure to negotiate a TLS
-session after a success response code, what happens is controlled by the
-&%tls_tempfail_tryclear%& option of the &(smtp)& transport. If it is false,
-delivery to this host is deferred, and other hosts (if available) are tried. If
-it is true, Exim attempts to deliver unencrypted after a 4&'xx'& response to
-STARTTLS, and if STARTTLS is accepted, but the subsequent TLS
-negotiation fails, Exim closes the current connection (because it is in an
-unknown state), opens a new one to the same host, and then tries the delivery
-unencrypted.
-
-The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)&
-transport provide the client with a certificate, which is passed to the server
-if it requests it. If the server is Exim, it will request a certificate only if
-&%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client.
-
-&*Note*&: Do not use a certificate which has the OCSP-must-staple extension,
-for client use (they are usable for server use).
-As the TLS protocol has no means for the client to staple before TLS 1.3 it will result
-in failed connections.
-
-If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it
-specifies a collection of expected server certificates.
-These may be
-the system default set (depending on library version),
-a file,
-or (depending on library version) a directory.
-The client verifies the server's certificate
-against this collection, taking into account any revoked certificates that are
-in the list defined by &%tls_crl%&.
-Failure to verify fails the TLS connection unless either of the
-&%tls_verify_hosts%& or &%tls_try_verify_hosts%& options are set.
-
-The &%tls_verify_hosts%& and &%tls_try_verify_hosts%& options restrict
-certificate verification to the listed servers.  Verification either must
-or need not succeed respectively.
-
-The &%tls_verify_cert_hostnames%& option lists hosts for which additional
-checks are made: that the host name (the one in the DNS A record)
-is valid for the certificate.
-The option defaults to always checking.
-
-The &(smtp)& transport has two OCSP-related options:
-&%hosts_require_ocsp%&; a host-list for which a Certificate Status
-is requested and required for the connection to proceed.  The default
-value is empty.
-&%hosts_request_ocsp%&; a host-list for which (additionally)
-a Certificate Status is requested (but not necessarily verified).  The default
-value is "*" meaning that requests are made unless configured
-otherwise.
-
-The host(s) should also be in &%hosts_require_tls%&, and
-&%tls_verify_certificates%& configured for the transport,
-for OCSP to be relevant.
-
-If
-&%tls_require_ciphers%& is set on the &(smtp)& transport, it must contain a
-list of permitted cipher suites. If either of these checks fails, delivery to
-the current host is abandoned, and the &(smtp)& transport tries to deliver to
-alternative hosts, if any.
-
- &*Note*&:
-These options must be set in the &(smtp)& transport for Exim to use TLS when it
-is operating as a client. Exim does not assume that a server certificate (set
-by the global options of the same name) should also be used when operating as a
-client.
-
-.vindex "&$host$&"
-.vindex "&$host_address$&"
-All the TLS options in the &(smtp)& transport are expanded before use, with
-&$host$& and &$host_address$& containing the name and address of the server to
-which the client is connected. Forced failure of an expansion causes Exim to
-behave as if the relevant option were unset.
-
-.vindex &$tls_out_bits$&
-.vindex &$tls_out_cipher$&
-.vindex &$tls_out_peerdn$&
-.vindex &$tls_out_sni$&
-Before an SMTP connection is established, the
-&$tls_out_bits$&, &$tls_out_cipher$&, &$tls_out_peerdn$& and &$tls_out_sni$&
-variables are emptied. (Until the first connection, they contain the values
-that were set when the message was received.) If STARTTLS is subsequently
-successfully obeyed, these variables are set to the relevant values for the
-outgoing connection.
-
-
-
-.section "Use of TLS Server Name Indication" "SECTtlssni"
-.cindex "TLS" "Server Name Indication"
-.vindex "&$tls_in_sni$&"
-.oindex "&%tls_in_sni%&"
-With TLS1.0 or above, there is an extension mechanism by which extra
-information can be included at various points in the protocol.  One of these
-extensions, documented in RFC 6066 (and before that RFC 4366) is
-&"Server Name Indication"&, commonly &"SNI"&.  This extension is sent by the
-client in the initial handshake, so that the server can examine the servername
-within and possibly choose to use different certificates and keys (and more)
-for this session.
-
-This is analogous to HTTP's &"Host:"& header, and is the main mechanism by
-which HTTPS-enabled web-sites can be virtual-hosted, many sites to one IP
-address.
-
-With SMTP to MX, there are the same problems here as in choosing the identity
-against which to validate a certificate: you can't rely on insecure DNS to
-provide the identity which you then cryptographically verify.  So this will
-be of limited use in that environment.
-
-With SMTP to Submission, there is a well-defined hostname which clients are
-connecting to and can validate certificates against.  Thus clients &*can*&
-choose to include this information in the TLS negotiation.  If this becomes
-wide-spread, then hosters can choose to present different certificates to
-different clients.  Or even negotiate different cipher suites.
-
-The &%tls_sni%& option on an SMTP transport is an expanded string; the result,
-if not empty, will be sent on a TLS session as part of the handshake.  There's
-nothing more to it.  Choosing a sensible value not derived insecurely is the
-only point of caution.  The &$tls_out_sni$& variable will be set to this string
-for the lifetime of the client connection (including during authentication).
-
-Except during SMTP client sessions, if &$tls_in_sni$& is set then it is a string
-received from a client.
-It can be logged with the &%log_selector%& item &`+tls_sni`&.
-
-If the string &`tls_in_sni`& appears in the main section's &%tls_certificate%&
-option (prior to expansion) then the following options will be re-expanded
-during TLS session handshake, to permit alternative values to be chosen:
-
-.ilist
-&%tls_certificate%&
-.next
-&%tls_crl%&
-.next
-&%tls_privatekey%&
-.next
-&%tls_verify_certificates%&
-.next
-&%tls_ocsp_file%&
-.endlist
-
-Great care should be taken to deal with matters of case, various injection
-attacks in the string (&`../`& or SQL), and ensuring that a valid filename
-can always be referenced; it is important to remember that &$tls_in_sni$& is
-arbitrary unverified data provided prior to authentication.
-Further, the initial certificate is loaded before SNI has arrived, so
-an expansion for &%tls_certificate%& must have a default which is used
-when &$tls_in_sni$& is empty.
-
-The Exim developers are proceeding cautiously and so far no other TLS options
-are re-expanded.
-
-When Exim is built against OpenSSL, OpenSSL must have been built with support
-for TLS Extensions.  This holds true for OpenSSL 1.0.0+ and 0.9.8+ with
-enable-tlsext in EXTRACONFIGURE.  If you invoke &(openssl s_client -h)& and
-see &`-servername`& in the output, then OpenSSL has support.
-
-When Exim is built against GnuTLS, SNI support is available as of GnuTLS
-0.5.10.  (Its presence predates the current API which Exim uses, so if Exim
-built, then you have SNI support).
-
-
-
-.section "Multiple messages on the same encrypted TCP/IP connection" &&&
-         "SECTmulmessam"
-.cindex "multiple SMTP deliveries with TLS"
-.cindex "TLS" "multiple message deliveries"
-Exim sends multiple messages down the same TCP/IP connection by starting up
-an entirely new delivery process for each message, passing the socket from
-one process to the next. This implementation does not fit well with the use
-of TLS, because there is quite a lot of state information associated with a TLS
-connection, not just a socket identification. Passing all the state information
-to a new process is not feasible. Consequently, for sending using TLS Exim
-starts an additional proxy process for handling the encryption, piping the
-unencrypted data stream from and to the delivery processes.
-
-An older mode of operation can be enabled on a per-host basis by the
-&%hosts_noproxy_tls%& option on the &(smtp)& transport.  If the host matches
-this list the proxy process described above is not used; instead Exim
-shuts down an existing TLS session being run by the delivery process
-before passing the socket to a new process. The new process may then
-try to start a new TLS session, and if successful, may try to re-authenticate
-if AUTH is in use, before sending the next message.
-
-The RFC is not clear as to whether or not an SMTP session continues in clear
-after TLS has been shut down, or whether TLS may be restarted again later, as
-just described. However, if the server is Exim, this shutdown and
-reinitialization works. It is not known which (if any) other servers operate
-successfully if the client closes a TLS session and continues with unencrypted
-SMTP, but there are certainly some that do not work. For such servers, Exim
-should not pass the socket to another process, because the failure of the
-subsequent attempt to use it would cause Exim to record a temporary host error,
-and delay other deliveries to that host.
-
-To test for this case, Exim sends an EHLO command to the server after
-closing down the TLS session. If this fails in any way, the connection is
-closed instead of being passed to a new delivery process, but no retry
-information is recorded.
-
-There is also a manual override; you can set &%hosts_nopass_tls%& on the
-&(smtp)& transport to match those hosts for which Exim should not pass
-connections to new processes if TLS has been used.
-
-
-
-
-.section "Certificates and all that" "SECTcerandall"
-.cindex "certificate" "references to discussion"
-In order to understand fully how TLS works, you need to know about
-certificates, certificate signing, and certificate authorities.
-This is a large topic and an introductory guide is unsuitable for the Exim
-reference manual, so instead we provide pointers to existing documentation.
-
-The Apache web-server was for a long time the canonical guide, so their
-documentation is a good place to start; their SSL module's Introduction
-document is currently at
-.display
-&url(https://httpd.apache.org/docs/current/ssl/ssl_intro.html)
-.endd
-and their FAQ is at
-.display
-&url(https://httpd.apache.org/docs/current/ssl/ssl_faq.html)
-.endd
-
-Eric Rescorla's book, &'SSL and TLS'&, published by Addison-Wesley (ISBN
-0-201-61598-3) in 2001, contains both introductory and more in-depth
-descriptions.
-More recently Ivan Ristić's book &'Bulletproof SSL and TLS'&,
-published by Feisty Duck (ISBN 978-1907117046) in 2013 is good.
-Ivan is the author of the popular TLS testing tools at
-&url(https://www.ssllabs.com/).
-
-
-.section "Certificate chains" "SECID186"
-The file named by &%tls_certificate%& may contain more than one
-certificate. This is useful in the case where the certificate that is being
-sent is validated by an intermediate certificate which the other end does
-not have. Multiple certificates must be in the correct order in the file.
-First the host's certificate itself, then the first intermediate
-certificate to validate the issuer of the host certificate, then the next
-intermediate certificate to validate the issuer of the first intermediate
-certificate, and so on, until finally (optionally) the root certificate.
-The root certificate must already be trusted by the recipient for
-validation to succeed, of course, but if it's not preinstalled, sending the
-root certificate along with the rest makes it available for the user to
-install if the receiving end is a client MUA that can interact with a user.
-
-Note that certificates using MD5 are unlikely to work on today's Internet;
-even if your libraries allow loading them for use in Exim when acting as a
-server, increasingly clients will not accept such certificates.  The error
-diagnostics in such a case can be frustratingly vague.
-
-
-
-.section "Self-signed certificates" "SECID187"
-.cindex "certificate" "self-signed"
-You can create a self-signed certificate using the &'req'& command provided
-with OpenSSL, like this:
-. ==== Do not shorten the duration here without reading and considering
-. ==== the text below.  Please leave it at 9999 days.
-.code
-openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \
-            -days 9999 -nodes
-.endd
-&_file1_& and &_file2_& can be the same file; the key and the certificate are
-delimited and so can be identified independently. The &%-days%& option
-specifies a period for which the certificate is valid. The &%-nodes%& option is
-important: if you do not set it, the key is encrypted with a passphrase
-that you are prompted for, and any use that is made of the key causes more
-prompting for the passphrase. This is not helpful if you are going to use
-this certificate and key in an MTA, where prompting is not possible.
-
-. ==== I expect to still be working 26 years from now.  The less technical
-. ==== debt I create, in terms of storing up trouble for my later years, the
-. ==== happier I will be then.  We really have reached the point where we
-. ==== should start, at the very least, provoking thought and making folks
-. ==== pause before proceeding, instead of leaving all the fixes until two
-. ==== years before 2^31 seconds after the 1970 Unix epoch.
-. ==== -pdp, 2012
-NB: we are now past the point where 9999 days takes us past the 32-bit Unix
-epoch.  If your system uses unsigned time_t (most do) and is 32-bit, then
-the above command might produce a date in the past.  Think carefully about
-the lifetime of the systems you're deploying, and either reduce the duration
-of the certificate or reconsider your platform deployment.  (At time of
-writing, reducing the duration is the most likely choice, but the inexorable
-progression of time takes us steadily towards an era where this will not
-be a sensible resolution).
-
-A self-signed certificate made in this way is sufficient for testing, and
-may be adequate for all your requirements if you are mainly interested in
-encrypting transfers, and not in secure identification.
-
-However, many clients require that the certificate presented by the server be a
-user (also called &"leaf"& or &"site"&) certificate, and not a self-signed
-certificate. In this situation, the self-signed certificate described above
-must be installed on the client host as a trusted root &'certification
-authority'& (CA), and the certificate used by Exim must be a user certificate
-signed with that self-signed certificate.
-
-For information on creating self-signed CA certificates and using them to sign
-user certificates, see the &'General implementation overview'& chapter of the
-Open-source PKI book, available online at
-&url(https://sourceforge.net/projects/ospkibook/).
-.ecindex IIDencsmtp1
-.ecindex IIDencsmtp2
-
-
-
-.section DANE "SECDANE"
-.cindex DANE
-DNS-based Authentication of Named Entities, as applied to SMTP over TLS, provides assurance to a client that
-it is actually talking to the server it wants to rather than some attacker operating a Man In The Middle (MITM)
-operation.  The latter can terminate the TLS connection you make, and make another one to the server (so both
-you and the server still think you have an encrypted connection) and, if one of the "well known" set of
-Certificate Authorities has been suborned - something which *has* been seen already (2014), a verifiable
-certificate (if you're using normal root CAs, eg. the Mozilla set, as your trust anchors).
-
-What DANE does is replace the CAs with the DNS as the trust anchor.  The assurance is limited to a) the possibility
-that the DNS has been suborned, b) mistakes made by the admins of the target server.   The attack surface presented
-by (a) is thought to be smaller than that of the set of root CAs.
-
-It also allows the server to declare (implicitly) that connections to it should use TLS.  An MITM could simply
-fail to pass on a server's STARTTLS.
-
-DANE scales better than having to maintain (and side-channel communicate) copies of server certificates
-for every possible target server.  It also scales (slightly) better than having to maintain on an SMTP
-client a copy of the standard CAs bundle.  It also means not having to pay a CA for certificates.
-
-DANE requires a server operator to do three things: 1) run DNSSEC.  This provides assurance to clients
-that DNS lookups they do for the server have not been tampered with.  The domain MX record applying
-to this server, its A record, its TLSA record and any associated CNAME records must all be covered by
-DNSSEC.
-2) add TLSA DNS records.  These say what the server certificate for a TLS connection should be.
-3) offer a server certificate, or certificate chain, in TLS connections which is is anchored by one of the TLSA records.
-
-There are no changes to Exim specific to server-side operation of DANE.
-Support for client-side operation of DANE can be included at compile time by defining SUPPORT_DANE=yes
-in &_Local/Makefile_&.
-If it has been included, the macro "_HAVE_DANE" will be defined.
-
-A TLSA record consist of 4 fields, the "Certificate Usage", the
-"Selector", the "Matching type", and the "Certificate Association Data".
-For a detailed description of the TLSA record see
-&url(https://tools.ietf.org/html/rfc7671#page-5,RFC 7671).
-
-The TLSA record for the server may have "Certificate Usage" (1st) field of DANE-TA(2) or DANE-EE(3).
-These are the "Trust Anchor" and "End Entity" variants.
-The latter specifies the End Entity directly, i.e. the certificate involved is that of the server
-(and if only DANE-EE is used then it should be the sole one transmitted during the TLS handshake);
-this is appropriate for a single system, using a self-signed certificate.
-DANE-TA usage is effectively declaring a specific CA to be used; this might be a private CA or a public,
-well-known one.
-A private CA at simplest is just a self-signed certificate (with certain
-attributes) which is used to sign server certificates, but running one securely
-does require careful arrangement.
-With DANE-TA, as implemented in Exim and commonly in other MTAs,
-the server TLS handshake must transmit the entire certificate chain from CA to server-certificate.
-DANE-TA is commonly used for several services and/or servers, each having a TLSA query-domain CNAME record,
-all of which point to a single TLSA record.
-DANE-TA and DANE-EE can both be used together.
-
-Our recommendation is to use DANE with a certificate from a public CA,
-because this enables a variety of strategies for remote clients to verify
-your certificate.
-You can then publish information both via DANE and another technology,
-"MTA-STS", described below.
-
-When you use DANE-TA to publish trust anchor information, you ask entities
-outside your administrative control to trust the Certificate Authority for
-connections to you.
-If using a private CA then you should expect others to still apply the
-technical criteria they'd use for a public CA to your certificates.
-In particular, you should probably try to follow current best practices for CA
-operation around hash algorithms and key sizes.
-Do not expect other organizations to lower their security expectations just
-because a particular profile might be reasonable for your own internal use.
-
-When this text was last updated, this in practice means to avoid use of SHA-1
-and MD5; if using RSA to use key sizes of at least 2048 bits (and no larger
-than 4096, for interoperability); to use keyUsage fields correctly; to use
-random serial numbers.
-The list of requirements is subject to change as best practices evolve.
-If you're not already using a private CA, or it doesn't meet these
-requirements, then we encourage you to avoid all these issues and use a public
-CA such as &url(https://letsencrypt.org/,Let's Encrypt) instead.
-
-The TLSA record should have a "Selector" (2nd) field of SPKI(1) and
-a "Matching Type" (3rd) field of SHA2-512(2).
-
-For the "Certificate Authority Data" (4th) field, commands like
-
-.code
-  openssl x509 -pubkey -noout <certificate.pem \
-  | openssl rsa -outform der -pubin 2>/dev/null \
-  | openssl sha512 \
-  | awk '{print $2}'
-.endd
-
-are workable to create a hash of the certificate's public key.
-
-An example TLSA record for DANE-EE(3), SPKI(1), and SHA-512 (2) looks like
-
-.code
-  _25._tcp.mail.example.com. TLSA 3 1 2 8BA8A336E...
-.endd
-
-At the time of writing, &url(https://www.huque.com/bin/gen_tlsa)
-is useful for quickly generating TLSA records.
-
-
-For use with the DANE-TA model, server certificates must have a correct name (SubjectName or SubjectAltName).
-
-The Certificate issued by the CA published in the DANE-TA model should be
-issued using a strong hash algorithm.
-Exim, and importantly various other MTAs sending to you, will not
-re-enable hash algorithms which have been disabled by default in TLS
-libraries.
-This means no MD5 and no SHA-1.  SHA2-256 is the minimum for reliable
-interoperability (and probably the maximum too, in 2018).
-
-The use of OCSP-stapling should be considered, allowing for fast revocation of certificates (which would otherwise
-be limited by the DNS TTL on the TLSA records).  However, this is likely to only be usable with DANE-TA.  NOTE: the
-default of requesting OCSP for all hosts is modified iff DANE is in use, to:
-
-.code
-  hosts_request_ocsp = ${if or { {= {0}{$tls_out_tlsa_usage}} \
-				 {= {4}{$tls_out_tlsa_usage}} } \
-                         {*}{}}
-.endd
-
-The (new) variable &$tls_out_tlsa_usage$& is a bitfield with numbered bits set for TLSA record usage codes.
-The zero above means DANE was not in use, the four means that only DANE-TA usage TLSA records were
-found. If the definition of &%hosts_request_ocsp%& includes the
-string "tls_out_tlsa_usage", they are re-expanded in time to
-control the OCSP request.
-
-This modification of hosts_request_ocsp is only done if it has the default value of "*".  Admins who change it, and
-those who use &%hosts_require_ocsp%&, should consider the interaction with DANE in their OCSP settings.
-
-
-For client-side DANE there are three new smtp transport options, &%hosts_try_dane%&, &%hosts_require_dane%&
-and &%dane_require_tls_ciphers%&.
-The &"require"& variant will result in failure if the target host is not
-DNSSEC-secured. To get DNSSEC-secured hostname resolution, use
-the &%dnssec_request_domains%& router or transport option.
-
-DANE will only be usable if the target host has DNSSEC-secured MX, A and TLSA records.
-
-A TLSA lookup will be done if either of the above options match and the host-lookup succeeded using dnssec.
-If a TLSA lookup is done and succeeds, a DANE-verified TLS connection
-will be required for the host.  If it does not, the host will not
-be used; there is no fallback to non-DANE or non-TLS.
-
-If DANE is requested and usable, then the TLS cipher list configuration
-prefers to use the option &%dane_require_tls_ciphers%& and falls
-back to &%tls_require_ciphers%& only if that is unset.
-This lets you configure "decent crypto" for DANE and "better than nothing
-crypto" as the default.  Note though that while GnuTLS lets the string control
-which versions of TLS/SSL will be negotiated, OpenSSL does not and you're
-limited to ciphersuite constraints.
-
-If DANE is requested and useable (see above) the following transport options are ignored:
-.code
-  hosts_require_tls
-  tls_verify_hosts
-  tls_try_verify_hosts
-  tls_verify_certificates
-  tls_crl
-  tls_verify_cert_hostnames
-.endd
-
-If DANE is not usable, whether requested or not, and CA-anchored
-verification evaluation is wanted, the above variables should be set appropriately.
-
-The router and transport option &%dnssec_request_domains%& must not be
-set to &"never"&, and &%dnssec_require_domains%& is ignored.
-
-If verification was successful using DANE then the "CV" item in the delivery log line will show as "CV=dane".
-
-There is a new variable &$tls_out_dane$& which will have "yes" if
-verification succeeded using DANE and "no" otherwise (only useful
-in combination with events; see &<<CHAPevents>>&),
-and a new variable &$tls_out_tlsa_usage$& (detailed above).
-
-.cindex DANE reporting
-An event (see &<<CHAPevents>>&) of type "dane:fail" will be raised on failures
-to achieve DANE-verified connection, if one was either requested and offered, or
-required.  This is intended to support TLS-reporting as defined in
-&url(https://tools.ietf.org/html/draft-ietf-uta-smtp-tlsrpt-17).
-The &$event_data$& will be one of the Result Types defined in
-Section 4.3 of that document.
-
-Under GnuTLS, DANE is only supported from version 3.0.0 onwards.
-
-DANE is specified in published RFCs and decouples certificate authority trust
-selection from a "race to the bottom" of "you must trust everything for mail
-to get through".  There is an alternative technology called MTA-STS, which
-instead publishes MX trust anchor information on an HTTPS website.  At the
-time this text was last updated, MTA-STS was still a draft, not yet an RFC.
-Exim has no support for MTA-STS as a client, but Exim mail server operators
-can choose to publish information describing their TLS configuration using
-MTA-STS to let those clients who do use that protocol derive trust
-information.
-
-The MTA-STS design requires a certificate from a public Certificate Authority
-which is recognized by clients sending to you.
-That selection of which CAs are trusted by others is outside your control.
-
-The most interoperable course of action is probably to use
-&url(https://letsencrypt.org/,Let's Encrypt), with automated certificate
-renewal; to publish the anchor information in DNSSEC-secured DNS via TLSA
-records for DANE clients (such as Exim and Postfix) and to publish anchor
-information for MTA-STS as well.  This is what is done for the &'exim.org'&
-domain itself (with caveats around occasionally broken MTA-STS because of
-incompatible specification changes prior to reaching RFC status).
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "Access control lists" "CHAPACL"
-.scindex IIDacl "&ACL;" "description"
-.cindex "control of incoming mail"
-.cindex "message" "controlling incoming"
-.cindex "policy control" "access control lists"
-Access Control Lists (ACLs) are defined in a separate section of the runtime
-configuration file, headed by &"begin acl"&. Each ACL definition starts with a
-name, terminated by a colon. Here is a complete ACL section that contains just
-one very small ACL:
-.code
-begin acl
-small_acl:
-  accept   hosts = one.host.only
-.endd
-You can have as many lists as you like in the ACL section, and the order in
-which they appear does not matter. The lists are self-terminating.
-
-The majority of ACLs are used to control Exim's behaviour when it receives
-certain SMTP commands. This applies both to incoming TCP/IP connections, and
-when a local process submits a message using SMTP by specifying the &%-bs%&
-option. The most common use is for controlling which recipients are accepted
-in incoming messages. In addition, you can define an ACL that is used to check
-local non-SMTP messages. The default configuration file contains an example of
-a realistic ACL for checking RCPT commands. This is discussed in chapter
-&<<CHAPdefconfil>>&.
-
-
-.section "Testing ACLs" "SECID188"
-The &%-bh%& command line option provides a way of testing your ACL
-configuration locally by running a fake SMTP session with which you interact.
-
-
-.section "Specifying when ACLs are used" "SECID189"
-.cindex "&ACL;" "options for specifying"
-In order to cause an ACL to be used, you have to name it in one of the relevant
-options in the main part of the configuration. These options are:
-.cindex "AUTH" "ACL for"
-.cindex "DATA" "ACLs for"
-.cindex "ETRN" "ACL for"
-.cindex "EXPN" "ACL for"
-.cindex "HELO" "ACL for"
-.cindex "EHLO" "ACL for"
-.cindex "DKIM" "ACL for"
-.cindex "MAIL" "ACL for"
-.cindex "QUIT, ACL for"
-.cindex "RCPT" "ACL for"
-.cindex "STARTTLS, ACL for"
-.cindex "VRFY" "ACL for"
-.cindex "SMTP" "connection, ACL for"
-.cindex "non-SMTP messages" "ACLs for"
-.cindex "MIME content scanning" "ACL for"
-.cindex "PRDR" "ACL for"
-
-.table2 140pt
-.irow &%acl_not_smtp%&         "ACL for non-SMTP messages"
-.irow &%acl_not_smtp_mime%&    "ACL for non-SMTP MIME parts"
-.irow &%acl_not_smtp_start%&   "ACL at start of non-SMTP message"
-.irow &%acl_smtp_auth%&        "ACL for AUTH"
-.irow &%acl_smtp_connect%&     "ACL for start of SMTP connection"
-.irow &%acl_smtp_data%&        "ACL after DATA is complete"
-.irow &%acl_smtp_data_prdr%&   "ACL for each recipient, after DATA is complete"
-.irow &%acl_smtp_dkim%&        "ACL for each DKIM signer"
-.irow &%acl_smtp_etrn%&        "ACL for ETRN"
-.irow &%acl_smtp_expn%&        "ACL for EXPN"
-.irow &%acl_smtp_helo%&        "ACL for HELO or EHLO"
-.irow &%acl_smtp_mail%&        "ACL for MAIL"
-.irow &%acl_smtp_mailauth%&    "ACL for the AUTH parameter of MAIL"
-.irow &%acl_smtp_mime%&        "ACL for content-scanning MIME parts"
-.irow &%acl_smtp_notquit%&     "ACL for non-QUIT terminations"
-.irow &%acl_smtp_predata%&     "ACL at start of DATA command"
-.irow &%acl_smtp_quit%&        "ACL for QUIT"
-.irow &%acl_smtp_rcpt%&        "ACL for RCPT"
-.irow &%acl_smtp_starttls%&    "ACL for STARTTLS"
-.irow &%acl_smtp_vrfy%&        "ACL for VRFY"
-.endtable
-
-For example, if you set
-.code
-acl_smtp_rcpt = small_acl
-.endd
-the little ACL defined above is used whenever Exim receives a RCPT command
-in an SMTP dialogue. The majority of policy tests on incoming messages can be
-done when RCPT commands arrive. A rejection of RCPT should cause the
-sending MTA to give up on the recipient address contained in the RCPT
-command, whereas rejection at other times may cause the client MTA to keep on
-trying to deliver the message. It is therefore recommended that you do as much
-testing as possible at RCPT time.
-
-
-.section "The non-SMTP ACLs" "SECID190"
-.cindex "non-SMTP messages" "ACLs for"
-The non-SMTP ACLs apply to all non-interactive incoming messages, that is, they
-apply to batched SMTP as well as to non-SMTP messages. (Batched SMTP is not
-really SMTP.) Many of the ACL conditions (for example, host tests, and tests on
-the state of the SMTP connection such as encryption and authentication) are not
-relevant and are forbidden in these ACLs. However, the sender and recipients
-are known, so the &%senders%& and &%sender_domains%& conditions and the
-&$sender_address$& and &$recipients$& variables can be used. Variables such as
-&$authenticated_sender$& are also available. You can specify added header lines
-in any of these ACLs.
-
-The &%acl_not_smtp_start%& ACL is run right at the start of receiving a
-non-SMTP message, before any of the message has been read. (This is the
-analogue of the &%acl_smtp_predata%& ACL for SMTP input.) In the case of
-batched SMTP input, it runs after the DATA command has been reached. The
-result of this ACL is ignored; it cannot be used to reject a message. If you
-really need to, you could set a value in an ACL variable here and reject based
-on that in the &%acl_not_smtp%& ACL. However, this ACL can be used to set
-controls, and in particular, it can be used to set
-.code
-control = suppress_local_fixups
-.endd
-This cannot be used in the other non-SMTP ACLs because by the time they are
-run, it is too late.
-
-The &%acl_not_smtp_mime%& ACL is available only when Exim is compiled with the
-content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
-
-The &%acl_not_smtp%& ACL is run just before the &[local_scan()]& function. Any
-kind of rejection is treated as permanent, because there is no way of sending a
-temporary error for these kinds of message.
-
-
-.section "The SMTP connect ACL" "SECID191"
-.cindex "SMTP" "connection, ACL for"
-.oindex &%smtp_banner%&
-The ACL test specified by &%acl_smtp_connect%& happens at the start of an SMTP
-session, after the test specified by &%host_reject_connection%& (which is now
-an anomaly) and any TCP Wrappers testing (if configured). If the connection is
-accepted by an &%accept%& verb that has a &%message%& modifier, the contents of
-the message override the banner message that is otherwise specified by the
-&%smtp_banner%& option.
-
-
-.section "The EHLO/HELO ACL" "SECID192"
-.cindex "EHLO" "ACL for"
-.cindex "HELO" "ACL for"
-The ACL test specified by &%acl_smtp_helo%& happens when the client issues an
-EHLO or HELO command, after the tests specified by &%helo_accept_junk_hosts%&,
-&%helo_allow_chars%&, &%helo_verify_hosts%&, and &%helo_try_verify_hosts%&.
-Note that a client may issue more than one EHLO or HELO command in an SMTP
-session, and indeed is required to issue a new EHLO or HELO after successfully
-setting up encryption following a STARTTLS command.
-
-Note also that a deny neither forces the client to go away nor means that
-mail will be refused on the connection.  Consider checking for
-&$sender_helo_name$& being defined in a MAIL or RCPT ACL to do that.
-
-If the command is accepted by an &%accept%& verb that has a &%message%&
-modifier, the message may not contain more than one line (it will be truncated
-at the first newline and a panic logged if it does). Such a message cannot
-affect the EHLO options that are listed on the second and subsequent lines of
-an EHLO response.
-
-
-.section "The DATA ACLs" "SECID193"
-.cindex "DATA" "ACLs for"
-Two ACLs are associated with the DATA command, because it is two-stage
-command, with two responses being sent to the client.
-When the DATA command is received, the ACL defined by &%acl_smtp_predata%&
-is obeyed. This gives you control after all the RCPT commands, but before
-the message itself is received. It offers the opportunity to give a negative
-response to the DATA command before the data is transmitted. Header lines
-added by MAIL or RCPT ACLs are not visible at this time, but any that
-are defined here are visible when the &%acl_smtp_data%& ACL is run.
-
-You cannot test the contents of the message, for example, to verify addresses
-in the headers, at RCPT time or when the DATA command is received. Such
-tests have to appear in the ACL that is run after the message itself has been
-received, before the final response to the DATA command is sent. This is
-the ACL specified by &%acl_smtp_data%&, which is the second ACL that is
-associated with the DATA command.
-
-.cindex CHUNKING "BDAT command"
-.cindex BDAT "SMTP command"
-.cindex "RFC 3030" CHUNKING
-If CHUNKING was advertised and a BDAT command sequence is received,
-the &%acl_smtp_predata%& ACL is not run.
-. XXX why not?  It should be possible, for the first BDAT.
-The &%acl_smtp_data%& is run after the last BDAT command and all of
-the data specified is received.
-
-For both of these ACLs, it is not possible to reject individual recipients. An
-error response rejects the entire message. Unfortunately, it is known that some
-MTAs do not treat hard (5&'xx'&) responses to the DATA command (either
-before or after the data) correctly &-- they keep the message on their queues
-and try again later, but that is their problem, though it does waste some of
-your resources.
-
-The &%acl_smtp_data%& ACL is run after
-the &%acl_smtp_data_prdr%&,
-the &%acl_smtp_dkim%&
-and the &%acl_smtp_mime%& ACLs.
-
-.section "The SMTP DKIM ACL" "SECTDKIMACL"
-The &%acl_smtp_dkim%& ACL is available only when Exim is compiled with DKIM support
-enabled (which is the default).
-
-The ACL test specified by &%acl_smtp_dkim%& happens after a message has been
-received, and is executed for each DKIM signature found in a message.  If not
-otherwise specified, the default action is to accept.
-
-This ACL is evaluated before &%acl_smtp_mime%& and &%acl_smtp_data%&.
-
-For details on the operation of DKIM, see section &<<SECDKIM>>&.
-
-
-.section "The SMTP MIME ACL" "SECID194"
-The &%acl_smtp_mime%& option is available only when Exim is compiled with the
-content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
-
-This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
-
-
-.section "The SMTP PRDR ACL" "SECTPRDRACL"
-.cindex "PRDR" "ACL for"
-.oindex "&%prdr_enable%&"
-The &%acl_smtp_data_prdr%& ACL is available only when Exim is compiled
-with PRDR support enabled (which is the default).
-It becomes active only when the PRDR feature is negotiated between
-client and server for a message, and more than one recipient
-has been accepted.
-
-The ACL test specified by &%acl_smtp_data_prdr%& happens after a message
-has been received, and is executed once for each recipient of the message
-with &$local_part$& and &$domain$& valid.
-The test may accept, defer or deny for individual recipients.
-The &%acl_smtp_data%& will still be called after this ACL and
-can reject the message overall, even if this ACL has accepted it
-for some or all recipients.
-
-PRDR may be used to support per-user content filtering.  Without it
-one must defer any recipient after the first that has a different
-content-filter configuration.  With PRDR, the RCPT-time check
-.cindex "PRDR" "variable for"
-for this can be disabled when the variable &$prdr_requested$&
-is &"yes"&.
-Any required difference in behaviour of the main DATA-time
-ACL should however depend on the PRDR-time ACL having run, as Exim
-will avoid doing so in some situations (e.g. single-recipient mails).
-
-See also the &%prdr_enable%& global option
-and the &%hosts_try_prdr%& smtp transport option.
-
-This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
-If the ACL is not defined, processing completes as if
-the feature was not requested by the client.
-
-.section "The QUIT ACL" "SECTQUITACL"
-.cindex "QUIT, ACL for"
-The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL
-does not affect the response code to QUIT, which is always 221. Thus, the ACL
-does not in fact control any access.
-For this reason, it may only accept
-or warn as its final result.
-
-This ACL can be used for tasks such as custom logging at the end of an SMTP
-session. For example, you can use ACL variables in other ACLs to count
-messages, recipients, etc., and log the totals at QUIT time using one or
-more &%logwrite%& modifiers on a &%warn%& verb.
-
-&*Warning*&: Only the &$acl_c$&&'x'& variables can be used for this, because
-the &$acl_m$&&'x'& variables are reset at the end of each incoming message.
-
-You do not need to have a final &%accept%&, but if you do, you can use a
-&%message%& modifier to specify custom text that is sent as part of the 221
-response to QUIT.
-
-This ACL is run only for a &"normal"& QUIT. For certain kinds of disastrous
-failure (for example, failure to open a log file, or when Exim is bombing out
-because it has detected an unrecoverable error), all SMTP commands from the
-client are given temporary error responses until QUIT is received or the
-connection is closed. In these special cases, the QUIT ACL does not run.
-
-
-.section "The not-QUIT ACL" "SECTNOTQUITACL"
-.vindex &$acl_smtp_notquit$&
-The not-QUIT ACL, specified by &%acl_smtp_notquit%&, is run in most cases when
-an SMTP session ends without sending QUIT. However, when Exim itself is in bad
-trouble, such as being unable to write to its log files, this ACL is not run,
-because it might try to do things (such as write to log files) that make the
-situation even worse.
-
-Like the QUIT ACL, this ACL is provided to make it possible to do customized
-logging or to gather statistics, and its outcome is ignored. The &%delay%&
-modifier is forbidden in this ACL, and the only permitted verbs are &%accept%&
-and &%warn%&.
-
-.vindex &$smtp_notquit_reason$&
-When the not-QUIT ACL is running, the variable &$smtp_notquit_reason$& is set
-to a string that indicates the reason for the termination of the SMTP
-connection. The possible values are:
-.table2
-.irow &`acl-drop`&                 "Another ACL issued a &%drop%& command"
-.irow &`bad-commands`&             "Too many unknown or non-mail commands"
-.irow &`command-timeout`&          "Timeout while reading SMTP commands"
-.irow &`connection-lost`&          "The SMTP connection has been lost"
-.irow &`data-timeout`&             "Timeout while reading message data"
-.irow &`local-scan-error`&         "The &[local_scan()]& function crashed"
-.irow &`local-scan-timeout`&       "The &[local_scan()]& function timed out"
-.irow &`signal-exit`&              "SIGTERM or SIGINT"
-.irow &`synchronization-error`&    "SMTP synchronization error"
-.irow &`tls-failed`&               "TLS failed to start"
-.endtable
-In most cases when an SMTP connection is closed without having received QUIT,
-Exim sends an SMTP response message before actually closing the connection.
-With the exception of the &`acl-drop`& case, the default message can be
-overridden by the &%message%& modifier in the not-QUIT ACL. In the case of a
-&%drop%& verb in another ACL, it is the message from the other ACL that is
-used.
-
-
-.section "Finding an ACL to use" "SECID195"
-.cindex "&ACL;" "finding which to use"
-The value of an &%acl_smtp_%&&'xxx'& option is expanded before use, so
-you can use different ACLs in different circumstances. For example,
-.code
-acl_smtp_rcpt = ${if ={25}{$interface_port} \
-                     {acl_check_rcpt} {acl_check_rcpt_submit} }
-.endd
-In the default configuration file there are some example settings for
-providing an RFC 4409 message &"submission"& service on port 587 and
-an RFC 8314 &"submissions"& service on port 465. You can use a string
-expansion like this to choose an ACL for MUAs on these ports which is
-more appropriate for this purpose than the default ACL on port 25.
-
-The expanded string does not have to be the name of an ACL in the
-configuration file; there are other possibilities. Having expanded the
-string, Exim searches for an ACL as follows:
-
-.ilist
-If the string begins with a slash, Exim uses it as a filename, and reads its
-contents as an ACL. The lines are processed in the same way as lines in the
-Exim configuration file. In particular, continuation lines are supported, blank
-lines are ignored, as are lines whose first non-whitespace character is &"#"&.
-If the file does not exist or cannot be read, an error occurs (typically
-causing a temporary failure of whatever caused the ACL to be run). For example:
-.code
-acl_smtp_data = /etc/acls/\
-  ${lookup{$sender_host_address}lsearch\
-  {/etc/acllist}{$value}{default}}
-.endd
-This looks up an ACL file to use on the basis of the host's IP address, falling
-back to a default if the lookup fails. If an ACL is successfully read from a
-file, it is retained in memory for the duration of the Exim process, so that it
-can be re-used without having to re-read the file.
-.next
-If the string does not start with a slash, and does not contain any spaces,
-Exim searches the ACL section of the configuration for an ACL whose name
-matches the string.
-.next
-If no named ACL is found, or if the string contains spaces, Exim parses
-the string as an inline ACL. This can save typing in cases where you just
-want to have something like
-.code
-acl_smtp_vrfy = accept
-.endd
-in order to allow free use of the VRFY command. Such a string may contain
-newlines; it is processed in the same way as an ACL that is read from a file.
-.endlist
-
-
-
-
-.section "ACL return codes" "SECID196"
-.cindex "&ACL;" "return codes"
-Except for the QUIT ACL, which does not affect the SMTP return code (see
-section &<<SECTQUITACL>>& above), the result of running an ACL is either
-&"accept"& or &"deny"&, or, if some test cannot be completed (for example, if a
-database is down), &"defer"&. These results cause 2&'xx'&, 5&'xx'&, and 4&'xx'&
-return codes, respectively, to be used in the SMTP dialogue. A fourth return,
-&"error"&, occurs when there is an error such as invalid syntax in the ACL.
-This also causes a 4&'xx'& return code.
-
-For the non-SMTP ACL, &"defer"& and &"error"& are treated in the same way as
-&"deny"&, because there is no mechanism for passing temporary errors to the
-submitters of non-SMTP messages.
-
-
-ACLs that are relevant to message reception may also return &"discard"&. This
-has the effect of &"accept"&, but causes either the entire message or an
-individual recipient address to be discarded. In other words, it is a
-blackholing facility. Use it with care.
-
-If the ACL for MAIL returns &"discard"&, all recipients are discarded, and no
-ACL is run for subsequent RCPT commands. The effect of &"discard"& in a
-RCPT ACL is to discard just the one recipient address. If there are no
-recipients left when the message's data is received, the DATA ACL is not
-run. A &"discard"& return from the DATA or the non-SMTP ACL discards all the
-remaining recipients. The &"discard"& return is not permitted for the
-&%acl_smtp_predata%& ACL.
-
-If the ACL for VRFY returns &"accept"&, a recipient verify (without callout)
-is done on the address and the result determines the SMTP response.
-
-
-.cindex "&[local_scan()]& function" "when all recipients discarded"
-The &[local_scan()]& function is always run, even if there are no remaining
-recipients; it may create new recipients.
-
-
-
-.section "Unset ACL options" "SECID197"
-.cindex "&ACL;" "unset options"
-The default actions when any of the &%acl_%&&'xxx'& options are unset are not
-all the same. &*Note*&: These defaults apply only when the relevant ACL is
-not defined at all. For any defined ACL, the default action when control
-reaches the end of the ACL statements is &"deny"&.
-
-For &%acl_smtp_quit%& and &%acl_not_smtp_start%& there is no default because
-these two are ACLs that are used only for their side effects. They cannot be
-used to accept or reject anything.
-
-For &%acl_not_smtp%&, &%acl_smtp_auth%&, &%acl_smtp_connect%&,
-&%acl_smtp_data%&, &%acl_smtp_helo%&, &%acl_smtp_mail%&, &%acl_smtp_mailauth%&,
-&%acl_smtp_mime%&, &%acl_smtp_predata%&, and &%acl_smtp_starttls%&, the action
-when the ACL is not defined is &"accept"&.
-
-For the others (&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&, and
-&%acl_smtp_vrfy%&), the action when the ACL is not defined is &"deny"&.
-This means that &%acl_smtp_rcpt%& must be defined in order to receive any
-messages over an SMTP connection. For an example, see the ACL in the default
-configuration file.
-
-
-
-
-.section "Data for message ACLs" "SECID198"
-.cindex "&ACL;" "data for message ACL"
-.vindex &$domain$&
-.vindex &$local_part$&
-.vindex &$sender_address$&
-.vindex &$sender_host_address$&
-.vindex &$smtp_command$&
-When a MAIL or RCPT ACL, or either of the DATA ACLs, is running, the variables
-that contain information about the host and the message's sender (for example,
-&$sender_host_address$& and &$sender_address$&) are set, and can be used in ACL
-statements. In the case of RCPT (but not MAIL or DATA), &$domain$& and
-&$local_part$& are set from the argument address. The entire SMTP command
-is available in &$smtp_command$&.
-
-When an ACL for the AUTH parameter of MAIL is running, the variables that
-contain information about the host are set, but &$sender_address$& is not yet
-set. Section &<<SECTauthparamail>>& contains a discussion of this parameter and
-how it is used.
-
-.vindex "&$message_size$&"
-The &$message_size$& variable is set to the value of the SIZE parameter on
-the MAIL command at MAIL, RCPT and pre-data time, or to -1 if
-that parameter is not given. The value is updated to the true message size by
-the time the final DATA ACL is run (after the message data has been
-received).
-
-.vindex "&$rcpt_count$&"
-.vindex "&$recipients_count$&"
-The &$rcpt_count$& variable increases by one for each RCPT command received.
-The &$recipients_count$& variable increases by one each time a RCPT command is
-accepted, so while an ACL for RCPT is being processed, it contains the number
-of previously accepted recipients. At DATA time (for both the DATA ACLs),
-&$rcpt_count$& contains the total number of RCPT commands, and
-&$recipients_count$& contains the total number of accepted recipients.
-
-
-
-
-
-.section "Data for non-message ACLs" "SECTdatfornon"
-.cindex "&ACL;" "data for non-message ACL"
-.vindex &$smtp_command_argument$&
-.vindex &$smtp_command$&
-When an ACL is being run for AUTH, EHLO, ETRN, EXPN, HELO, STARTTLS, or VRFY,
-the remainder of the SMTP command line is placed in &$smtp_command_argument$&,
-and the entire SMTP command is available in &$smtp_command$&.
-These variables can be tested using a &%condition%& condition. For example,
-here is an ACL for use with AUTH, which insists that either the session is
-encrypted, or the CRAM-MD5 authentication method is used. In other words, it
-does not permit authentication methods that use cleartext passwords on
-unencrypted connections.
-.code
-acl_check_auth:
-  accept encrypted = *
-  accept condition = ${if eq{${uc:$smtp_command_argument}}\
-                     {CRAM-MD5}}
-  deny   message   = TLS encryption or CRAM-MD5 required
-.endd
-(Another way of applying this restriction is to arrange for the authenticators
-that use cleartext passwords not to be advertised when the connection is not
-encrypted. You can use the generic &%server_advertise_condition%& authenticator
-option to do this.)
-
-
-
-.section "Format of an ACL" "SECID199"
-.cindex "&ACL;" "format of"
-.cindex "&ACL;" "verbs, definition of"
-An individual ACL consists of a number of statements. Each statement starts
-with a verb, optionally followed by a number of conditions and &"modifiers"&.
-Modifiers can change the way the verb operates, define error and log messages,
-set variables, insert delays, and vary the processing of accepted messages.
-
-If all the conditions are met, the verb is obeyed. The same condition may be
-used (with different arguments) more than once in the same statement. This
-provides a means of specifying an &"and"& conjunction between conditions. For
-example:
-.code
-deny  dnslists = list1.example
-      dnslists = list2.example
-.endd
-If there are no conditions, the verb is always obeyed. Exim stops evaluating
-the conditions and modifiers when it reaches a condition that fails. What
-happens then depends on the verb (and in one case, on a special modifier). Not
-all the conditions make sense at every testing point. For example, you cannot
-test a sender address in the ACL that is run for a VRFY command.
-
-
-.section "ACL verbs" "SECID200"
-The ACL verbs are as follows:
-
-.ilist
-.cindex "&%accept%& ACL verb"
-&%accept%&: If all the conditions are met, the ACL returns &"accept"&. If any
-of the conditions are not met, what happens depends on whether &%endpass%&
-appears among the conditions (for syntax see below). If the failing condition
-is before &%endpass%&, control is passed to the next ACL statement; if it is
-after &%endpass%&, the ACL returns &"deny"&. Consider this statement, used to
-check a RCPT command:
-.code
-accept domains = +local_domains
-       endpass
-       verify = recipient
-.endd
-If the recipient domain does not match the &%domains%& condition, control
-passes to the next statement. If it does match, the recipient is verified, and
-the command is accepted if verification succeeds. However, if verification
-fails, the ACL yields &"deny"&, because the failing condition is after
-&%endpass%&.
-
-The &%endpass%& feature has turned out to be confusing to many people, so its
-use is not recommended nowadays. It is always possible to rewrite an ACL so
-that &%endpass%& is not needed, and it is no longer used in the default
-configuration.
-
-.cindex "&%message%& ACL modifier" "with &%accept%&"
-If a &%message%& modifier appears on an &%accept%& statement, its action
-depends on whether or not &%endpass%& is present. In the absence of &%endpass%&
-(when an &%accept%& verb either accepts or passes control to the next
-statement), &%message%& can be used to vary the message that is sent when an
-SMTP command is accepted. For example, in a RCPT ACL you could have:
-.display
-&`accept  `&<&'some conditions'&>
-&`        message = OK, I will allow you through today`&
-.endd
-You can specify an SMTP response code, optionally followed by an &"extended
-response code"& at the start of the message, but the first digit must be the
-same as would be sent by default, which is 2 for an &%accept%& verb.
-
-If &%endpass%& is present in an &%accept%& statement, &%message%& specifies
-an error message that is used when access is denied. This behaviour is retained
-for backward compatibility, but current &"best practice"& is to avoid the use
-of &%endpass%&.
-
-
-.next
-.cindex "&%defer%& ACL verb"
-&%defer%&: If all the conditions are true, the ACL returns &"defer"& which, in
-an SMTP session, causes a 4&'xx'& response to be given. For a non-SMTP ACL,
-&%defer%& is the same as &%deny%&, because there is no way of sending a
-temporary error. For a RCPT command, &%defer%& is much the same as using a
-&(redirect)& router and &`:defer:`& while verifying, but the &%defer%& verb can
-be used in any ACL, and even for a recipient it might be a simpler approach.
-
-
-.next
-.cindex "&%deny%& ACL verb"
-&%deny%&: If all the conditions are met, the ACL returns &"deny"&. If any of
-the conditions are not met, control is passed to the next ACL statement. For
-example,
-.code
-deny dnslists = blackholes.mail-abuse.org
-.endd
-rejects commands from hosts that are on a DNS black list.
-
-
-.next
-.cindex "&%discard%& ACL verb"
-&%discard%&: This verb behaves like &%accept%&, except that it returns
-&"discard"& from the ACL instead of &"accept"&. It is permitted only on ACLs
-that are concerned with receiving messages. When all the conditions are true,
-the sending entity receives a &"success"& response. However, &%discard%& causes
-recipients to be discarded. If it is used in an ACL for RCPT, just the one
-recipient is discarded; if used for MAIL, DATA or in the non-SMTP ACL, all the
-message's recipients are discarded. Recipients that are discarded before DATA
-do not appear in the log line when the &%received_recipients%& log selector is set.
-
-If the &%log_message%& modifier is set when &%discard%& operates,
-its contents are added to the line that is automatically written to the log.
-The &%message%& modifier operates exactly as it does for &%accept%&.
-
-
-.next
-.cindex "&%drop%& ACL verb"
-&%drop%&: This verb behaves like &%deny%&, except that an SMTP connection is
-forcibly closed after the 5&'xx'& error message has been sent. For example:
-.code
-drop   message   = I don't take more than 20 RCPTs
-       condition = ${if > {$rcpt_count}{20}}
-.endd
-There is no difference between &%deny%& and &%drop%& for the connect-time ACL.
-The connection is always dropped after sending a 550 response.
-
-.next
-.cindex "&%require%& ACL verb"
-&%require%&: If all the conditions are met, control is passed to the next ACL
-statement. If any of the conditions are not met, the ACL returns &"deny"&. For
-example, when checking a RCPT command,
-.code
-require message = Sender did not verify
-        verify  = sender
-.endd
-passes control to subsequent statements only if the message's sender can be
-verified. Otherwise, it rejects the command. Note the positioning of the
-&%message%& modifier, before the &%verify%& condition. The reason for this is
-discussed in section &<<SECTcondmodproc>>&.
-
-.next
-.cindex "&%warn%& ACL verb"
-&%warn%&: If all the conditions are true, a line specified by the
-&%log_message%& modifier is written to Exim's main log. Control always passes
-to the next ACL statement. If any condition is false, the log line is not
-written. If an identical log line is requested several times in the same
-message, only one copy is actually written to the log. If you want to force
-duplicates to be written, use the &%logwrite%& modifier instead.
-
-If &%log_message%& is not present, a &%warn%& verb just checks its conditions
-and obeys any &"immediate"& modifiers (such as &%control%&, &%set%&,
-&%logwrite%&, &%add_header%&, and &%remove_header%&) that appear before the
-first failing condition. There is more about adding header lines in section
-&<<SECTaddheadacl>>&.
-
-If any condition on a &%warn%& statement cannot be completed (that is, there is
-some sort of defer), the log line specified by &%log_message%& is not written.
-This does not include the case of a forced failure from a lookup, which
-is considered to be a successful completion. After a defer, no further
-conditions or modifiers in the &%warn%& statement are processed. The incident
-is logged, and the ACL continues to be processed, from the next statement
-onwards.
-
-
-.vindex "&$acl_verify_message$&"
-When one of the &%warn%& conditions is an address verification that fails, the
-text of the verification failure message is in &$acl_verify_message$&. If you
-want this logged, you must set it up explicitly. For example:
-.code
-warn   !verify = sender
-       log_message = sender verify failed: $acl_verify_message
-.endd
-.endlist
-
-At the end of each ACL there is an implicit unconditional &%deny%&.
-
-As you can see from the examples above, the conditions and modifiers are
-written one to a line, with the first one on the same line as the verb, and
-subsequent ones on following lines. If you have a very long condition, you can
-continue it onto several physical lines by the usual backslash continuation
-mechanism. It is conventional to align the conditions vertically.
-
-
-
-.section "ACL variables" "SECTaclvariables"
-.cindex "&ACL;" "variables"
-There are some special variables that can be set during ACL processing. They
-can be used to pass information between different ACLs, different invocations
-of the same ACL in the same SMTP connection, and between ACLs and the routers,
-transports, and filters that are used to deliver a message. The names of these
-variables must begin with &$acl_c$& or &$acl_m$&, followed either by a digit or
-an underscore, but the remainder of the name can be any sequence of
-alphanumeric characters and underscores that you choose. There is no limit on
-the number of ACL variables. The two sets act as follows:
-.ilist
-The values of those variables whose names begin with &$acl_c$& persist
-throughout an SMTP connection. They are never reset. Thus, a value that is set
-while receiving one message is still available when receiving the next message
-on the same SMTP connection.
-.next
-The values of those variables whose names begin with &$acl_m$& persist only
-while a message is being received. They are reset afterwards. They are also
-reset by MAIL, RSET, EHLO, HELO, and after starting up a TLS session.
-.endlist
-
-When a message is accepted, the current values of all the ACL variables are
-preserved with the message and are subsequently made available at delivery
-time. The ACL variables are set by a modifier called &%set%&. For example:
-.code
-accept hosts = whatever
-       set acl_m4 = some value
-accept authenticated = *
-       set acl_c_auth = yes
-.endd
-&*Note*&: A leading dollar sign is not used when naming a variable that is to
-be set. If you want to set a variable without taking any action, you can use a
-&%warn%& verb without any other modifiers or conditions.
-
-.oindex &%strict_acl_vars%&
-What happens if a syntactically valid but undefined ACL variable is
-referenced depends on the setting of the &%strict_acl_vars%& option. If it is
-false (the default), an empty string is substituted; if it is true, an
-error is generated.
-
-Versions of Exim before 4.64 have a limited set of numbered variables, but
-their names are compatible, so there is no problem with upgrading.
-
-
-.section "Condition and modifier processing" "SECTcondmodproc"
-.cindex "&ACL;" "conditions; processing"
-.cindex "&ACL;" "modifiers; processing"
-An exclamation mark preceding a condition negates its result. For example:
-.code
-deny   domains = *.dom.example
-      !verify  = recipient
-.endd
-causes the ACL to return &"deny"& if the recipient domain ends in
-&'dom.example'& and the recipient address cannot be verified. Sometimes
-negation can be used on the right-hand side of a condition. For example, these
-two statements are equivalent:
-.code
-deny  hosts = !192.168.3.4
-deny !hosts =  192.168.3.4
-.endd
-However, for many conditions (&%verify%& being a good example), only left-hand
-side negation of the whole condition is possible.
-
-The arguments of conditions and modifiers are expanded. A forced failure
-of an expansion causes a condition to be ignored, that is, it behaves as if the
-condition is true. Consider these two statements:
-.code
-accept  senders = ${lookup{$host_name}lsearch\
-                  {/some/file}{$value}fail}
-accept  senders = ${lookup{$host_name}lsearch\
-                  {/some/file}{$value}{}}
-.endd
-Each attempts to look up a list of acceptable senders. If the lookup succeeds,
-the returned list is searched, but if the lookup fails the behaviour is
-different in the two cases. The &%fail%& in the first statement causes the
-condition to be ignored, leaving no further conditions. The &%accept%& verb
-therefore succeeds. The second statement, however, generates an empty list when
-the lookup fails. No sender can match an empty list, so the condition fails,
-and therefore the &%accept%& also fails.
-
-ACL modifiers appear mixed in with conditions in ACL statements. Some of them
-specify actions that are taken as the conditions for a statement are checked;
-others specify text for messages that are used when access is denied or a
-warning is generated. The &%control%& modifier affects the way an incoming
-message is handled.
-
-The positioning of the modifiers in an ACL statement is important, because the
-processing of a verb ceases as soon as its outcome is known. Only those
-modifiers that have already been encountered will take effect. For example,
-consider this use of the &%message%& modifier:
-.code
-require message = Can't verify sender
-        verify  = sender
-        message = Can't verify recipient
-        verify  = recipient
-        message = This message cannot be used
-.endd
-If sender verification fails, Exim knows that the result of the statement is
-&"deny"&, so it goes no further. The first &%message%& modifier has been seen,
-so its text is used as the error message. If sender verification succeeds, but
-recipient verification fails, the second message is used. If recipient
-verification succeeds, the third message becomes &"current"&, but is never used
-because there are no more conditions to cause failure.
-
-For the &%deny%& verb, on the other hand, it is always the last &%message%&
-modifier that is used, because all the conditions must be true for rejection to
-happen. Specifying more than one &%message%& modifier does not make sense, and
-the message can even be specified after all the conditions. For example:
-.code
-deny   hosts = ...
-      !senders = *@my.domain.example
-       message = Invalid sender from client host
-.endd
-The &"deny"& result does not happen until the end of the statement is reached,
-by which time Exim has set up the message.
-
-
-
-.section "ACL modifiers" "SECTACLmodi"
-.cindex "&ACL;" "modifiers; list of"
-The ACL modifiers are as follows:
-
-.vlist
-.vitem &*add_header*&&~=&~<&'text'&>
-This modifier specifies one or more header lines that are to be added to an
-incoming message, assuming, of course, that the message is ultimately
-accepted. For details, see section &<<SECTaddheadacl>>&.
-
-.vitem &*continue*&&~=&~<&'text'&>
-.cindex "&%continue%& ACL modifier"
-.cindex "database" "updating in ACL"
-This modifier does nothing of itself, and processing of the ACL always
-continues with the next condition or modifier. The value of &%continue%& is in
-the side effects of expanding its argument. Typically this could be used to
-update a database. It is really just a syntactic tidiness, to avoid having to
-write rather ugly lines like this:
-.display
-&`condition = ${if eq{0}{`&<&'some expansion'&>&`}{true}{true}}`&
-.endd
-Instead, all you need is
-.display
-&`continue = `&<&'some expansion'&>
-.endd
-
-.vitem &*control*&&~=&~<&'text'&>
-.cindex "&%control%& ACL modifier"
-This modifier affects the subsequent processing of the SMTP connection or of an
-incoming message that is accepted. The effect of the first type of control
-lasts for the duration of the connection, whereas the effect of the second type
-lasts only until the current message has been received. The message-specific
-controls always apply to the whole message, not to individual recipients,
-even if the &%control%& modifier appears in a RCPT ACL.
-
-As there are now quite a few controls that can be applied, they are described
-separately in section &<<SECTcontrols>>&. The &%control%& modifier can be used
-in several different ways. For example:
-
-. ==== As this is a nested list, any displays it contains must be indented
-. ==== as otherwise they are too far to the left. That comment applies only
-. ==== when xmlto and fop are used; formatting with sdop gets it right either
-. ==== way.
-
-.ilist
-It can be at the end of an &%accept%& statement:
-.code
-    accept  ...some conditions
-            control = queue
-.endd
-In this case, the control is applied when this statement yields &"accept"&, in
-other words, when the conditions are all true.
-
-.next
-It can be in the middle of an &%accept%& statement:
-.code
-    accept  ...some conditions...
-            control = queue
-            ...some more conditions...
-.endd
-If the first set of conditions are true, the control is applied, even if the
-statement does not accept because one of the second set of conditions is false.
-In this case, some subsequent statement must yield &"accept"& for the control
-to be relevant.
-
-.next
-It can be used with &%warn%& to apply the control, leaving the
-decision about accepting or denying to a subsequent verb. For
-example:
-.code
-    warn    ...some conditions...
-            control = freeze
-    accept  ...
-.endd
-This example of &%warn%& does not contain &%message%&, &%log_message%&, or
-&%logwrite%&, so it does not add anything to the message and does not write a
-log entry.
-
-.next
-If you want to apply a control unconditionally, you can use it with a
-&%require%& verb. For example:
-.code
-    require  control = no_multiline_responses
-.endd
-.endlist
-
-.vitem &*delay*&&~=&~<&'time'&>
-.cindex "&%delay%& ACL modifier"
-.oindex "&%-bh%&"
-This modifier may appear in any ACL except notquit. It causes Exim to wait for
-the time interval before proceeding. However, when testing Exim using the
-&%-bh%& option, the delay is not actually imposed (an appropriate message is
-output instead). The time is given in the usual Exim notation, and the delay
-happens as soon as the modifier is processed. In an SMTP session, pending
-output is flushed before the delay is imposed.
-
-Like &%control%&, &%delay%& can be used with &%accept%& or &%deny%&, for
-example:
-.code
-deny    ...some conditions...
-        delay = 30s
-.endd
-The delay happens if all the conditions are true, before the statement returns
-&"deny"&. Compare this with:
-.code
-deny    delay = 30s
-        ...some conditions...
-.endd
-which waits for 30s before processing the conditions. The &%delay%& modifier
-can also be used with &%warn%& and together with &%control%&:
-.code
-warn    ...some conditions...
-        delay = 2m
-        control = freeze
-accept  ...
-.endd
-
-If &%delay%& is encountered when the SMTP PIPELINING extension is in use,
-responses to several commands are no longer buffered and sent in one packet (as
-they would normally be) because all output is flushed before imposing the
-delay. This optimization is disabled so that a number of small delays do not
-appear to the client as one large aggregated delay that might provoke an
-unwanted timeout. You can, however, disable output flushing for &%delay%& by
-using a &%control%& modifier to set &%no_delay_flush%&.
-
-
-.vitem &*endpass*&
-.cindex "&%endpass%& ACL modifier"
-This modifier, which has no argument, is recognized only in &%accept%& and
-&%discard%& statements. It marks the boundary between the conditions whose
-failure causes control to pass to the next statement, and the conditions whose
-failure causes the ACL to return &"deny"&. This concept has proved to be
-confusing to some people, so the use of &%endpass%& is no longer recommended as
-&"best practice"&. See the description of &%accept%& above for more details.
-
-
-.vitem &*log_message*&&~=&~<&'text'&>
-.cindex "&%log_message%& ACL modifier"
-This modifier sets up a message that is used as part of the log message if the
-ACL denies access or a &%warn%& statement's conditions are true. For example:
-.code
-require log_message = wrong cipher suite $tls_in_cipher
-        encrypted   = DES-CBC3-SHA
-.endd
-&%log_message%& is also used when recipients are discarded by &%discard%&. For
-example:
-.display
-&`discard `&<&'some conditions'&>
-&`        log_message = Discarded $local_part@$domain because...`&
-.endd
-When access is denied, &%log_message%& adds to any underlying error message
-that may exist because of a condition failure. For example, while verifying a
-recipient address, a &':fail:'& redirection might have already set up a
-message.
-
-The message may be defined before the conditions to which it applies, because
-the string expansion does not happen until Exim decides that access is to be
-denied. This means that any variables that are set by the condition are
-available for inclusion in the message. For example, the &$dnslist_$&<&'xxx'&>
-variables are set after a DNS black list lookup succeeds. If the expansion of
-&%log_message%& fails, or if the result is an empty string, the modifier is
-ignored.
-
-.vindex "&$acl_verify_message$&"
-If you want to use a &%warn%& statement to log the result of an address
-verification, you can use &$acl_verify_message$& to include the verification
-error message.
-
-If &%log_message%& is used with a &%warn%& statement, &"Warning:"& is added to
-the start of the logged message. If the same warning log message is requested
-more than once while receiving  a single email message, only one copy is
-actually logged. If you want to log multiple copies, use &%logwrite%& instead
-of &%log_message%&. In the absence of &%log_message%& and &%logwrite%&, nothing
-is logged for a successful &%warn%& statement.
-
-If &%log_message%& is not present and there is no underlying error message (for
-example, from the failure of address verification), but &%message%& is present,
-the &%message%& text is used for logging rejections. However, if any text for
-logging contains newlines, only the first line is logged. In the absence of
-both &%log_message%& and &%message%&, a default built-in message is used for
-logging rejections.
-
-
-.vitem "&*log_reject_target*&&~=&~<&'log name list'&>"
-.cindex "&%log_reject_target%& ACL modifier"
-.cindex "logging in ACL" "specifying which log"
-This modifier makes it possible to specify which logs are used for messages
-about ACL rejections. Its argument is a colon-separated list of words that can
-be &"main"&, &"reject"&, or &"panic"&. The default is &`main:reject`&. The list
-may be empty, in which case a rejection is not logged at all. For example, this
-ACL fragment writes no logging information when access is denied:
-.display
-&`deny `&<&'some conditions'&>
-&`     log_reject_target =`&
-.endd
-This modifier can be used in SMTP and non-SMTP ACLs. It applies to both
-permanent and temporary rejections. Its effect lasts for the rest of the
-current ACL.
-
-
-.vitem &*logwrite*&&~=&~<&'text'&>
-.cindex "&%logwrite%& ACL modifier"
-.cindex "logging in ACL" "immediate"
-This modifier writes a message to a log file as soon as it is encountered when
-processing an ACL. (Compare &%log_message%&, which, except in the case of
-&%warn%& and &%discard%&, is used only if the ACL statement denies
-access.) The &%logwrite%& modifier can be used to log special incidents in
-ACLs. For example:
-.display
-&`accept `&<&'some special conditions'&>
-&`       control  = freeze`&
-&`       logwrite = froze message because ...`&
-.endd
-By default, the message is written to the main log. However, it may begin
-with a colon, followed by a comma-separated list of log names, and then
-another colon, to specify exactly which logs are to be written. For
-example:
-.code
-logwrite = :main,reject: text for main and reject logs
-logwrite = :panic: text for panic log only
-.endd
-
-
-.vitem &*message*&&~=&~<&'text'&>
-.cindex "&%message%& ACL modifier"
-This modifier sets up a text string that is expanded and used as a response
-message when an ACL statement terminates the ACL with an &"accept"&, &"deny"&,
-or &"defer"& response. (In the case of the &%accept%& and &%discard%& verbs,
-there is some complication if &%endpass%& is involved; see the description of
-&%accept%& for details.)
-
-The expansion of the message happens at the time Exim decides that the ACL is
-to end, not at the time it processes &%message%&. If the expansion fails, or
-generates an empty string, the modifier is ignored. Here is an example where
-&%message%& must be specified first, because the ACL ends with a rejection if
-the &%hosts%& condition fails:
-.code
-require  message = Host not recognized
-         hosts = 10.0.0.0/8
-.endd
-(Once a condition has failed, no further conditions or modifiers are
-processed.)
-
-.cindex "SMTP" "error codes"
-.oindex "&%smtp_banner%&
-For ACLs that are triggered by SMTP commands, the message is returned as part
-of the SMTP response. The use of &%message%& with &%accept%& (or &%discard%&)
-is meaningful only for SMTP, as no message is returned when a non-SMTP message
-is accepted. In the case of the connect ACL, accepting with a message modifier
-overrides the value of &%smtp_banner%&. For the EHLO/HELO ACL, a customized
-accept message may not contain more than one line (otherwise it will be
-truncated at the first newline and a panic logged), and it cannot affect the
-EHLO options.
-
-When SMTP is involved, the message may begin with an overriding response code,
-consisting of three digits optionally followed by an &"extended response code"&
-of the form &'n.n.n'&, each code being followed by a space. For example:
-.code
-deny  message = 599 1.2.3 Host not welcome
-      hosts = 192.168.34.0/24
-.endd
-The first digit of the supplied response code must be the same as would be sent
-by default. A panic occurs if it is not. Exim uses a 550 code when it denies
-access, but for the predata ACL, note that the default success code is 354, not
-2&'xx'&.
-
-Notwithstanding the previous paragraph, for the QUIT ACL, unlike the others,
-the message modifier cannot override the 221 response code.
-
-The text in a &%message%& modifier is literal; any quotes are taken as
-literals, but because the string is expanded, backslash escapes are processed
-anyway. If the message contains newlines, this gives rise to a multi-line SMTP
-response.
-
-.vindex "&$acl_verify_message$&"
-For ACLs that are called by an &%acl =%& ACL condition, the message is
-stored in &$acl_verify_message$&, from which the calling ACL may use it.
-
-If &%message%& is used on a statement that verifies an address, the message
-specified overrides any message that is generated by the verification process.
-However, the original message is available in the variable
-&$acl_verify_message$&, so you can incorporate it into your message if you
-wish. In particular, if you want the text from &%:fail:%& items in &(redirect)&
-routers to be passed back as part of the SMTP response, you should either not
-use a &%message%& modifier, or make use of &$acl_verify_message$&.
-
-For compatibility with previous releases of Exim, a &%message%& modifier that
-is used with a &%warn%& verb behaves in a similar way to the &%add_header%&
-modifier, but this usage is now deprecated. However, &%message%& acts only when
-all the conditions are true, wherever it appears in an ACL command, whereas
-&%add_header%& acts as soon as it is encountered. If &%message%& is used with
-&%warn%& in an ACL that is not concerned with receiving a message, it has no
-effect.
-
-
-.vitem &*queue*&&~=&~<&'text'&>
-.cindex "&%queue%& ACL modifier"
-.cindex "named queues" "selecting in ACL"
-This modifier specifies the use of a named queue for spool files
-for the message.
-It can only be used before the message is received (i.e. not in
-the DATA ACL).
-This could be used, for example, for known high-volume burst sources
-of traffic, or for quarantine of messages.
-Separate queue-runner processes will be needed for named queues.
-If the text after expansion is empty, the default queue is used.
-
-
-.vitem &*remove_header*&&~=&~<&'text'&>
-This modifier specifies one or more header names in a colon-separated list
- that are to be removed from an incoming message, assuming, of course, that
-the message is ultimately accepted. For details, see section &<<SECTremoveheadacl>>&.
-
-
-.vitem &*set*&&~<&'acl_name'&>&~=&~<&'value'&>
-.cindex "&%set%& ACL modifier"
-This modifier puts a value into one of the ACL variables (see section
-&<<SECTaclvariables>>&).
-
-
-.vitem &*udpsend*&&~=&~<&'parameters'&>
-.cindex "UDP communications"
-This modifier sends a UDP packet, for purposes such as statistics
-collection or behaviour monitoring. The parameters are expanded, and
-the result of the expansion must be a colon-separated list consisting
-of a destination server, port number, and the packet contents. The
-server can be specified as a host name or IPv4 or IPv6 address. The
-separator can be changed with the usual angle bracket syntax. For
-example, you might want to collect information on which hosts connect
-when:
-.code
-udpsend = <; 2001:dB8::dead:beef ; 1234 ;\
-             $tod_zulu $sender_host_address
-.endd
-.endlist
-
-
-
-
-.section "Use of the control modifier" "SECTcontrols"
-.cindex "&%control%& ACL modifier"
-The &%control%& modifier supports the following settings:
-
-.vlist
-.vitem &*control&~=&~allow_auth_unadvertised*&
-This modifier allows a client host to use the SMTP AUTH command even when it
-has not been advertised in response to EHLO. Furthermore, because there are
-apparently some really broken clients that do this, Exim will accept AUTH after
-HELO (rather than EHLO) when this control is set. It should be used only if you
-really need it, and you should limit its use to those broken clients that do
-not work without it. For example:
-.code
-warn hosts   = 192.168.34.25
-     control = allow_auth_unadvertised
-.endd
-Normally, when an Exim server receives an AUTH command, it checks the name of
-the authentication mechanism that is given in the command to ensure that it
-matches an advertised mechanism. When this control is set, the check that a
-mechanism has been advertised is bypassed. Any configured mechanism can be used
-by the client. This control is permitted only in the connection and HELO ACLs.
-
-
-.vitem &*control&~=&~caseful_local_part*& &&&
-       &*control&~=&~caselower_local_part*&
-.cindex "&ACL;" "case of local part in"
-.cindex "case of local parts"
-.vindex "&$local_part$&"
-These two controls are permitted only in the ACL specified by &%acl_smtp_rcpt%&
-(that is, during RCPT processing). By default, the contents of &$local_part$&
-are lower cased before ACL processing. If &"caseful_local_part"& is specified,
-any uppercase letters in the original local part are restored in &$local_part$&
-for the rest of the ACL, or until a control that sets &"caselower_local_part"&
-is encountered.
-
-These controls affect only the current recipient. Moreover, they apply only to
-local part handling that takes place directly in the ACL (for example, as a key
-in lookups). If a test to verify the recipient is obeyed, the case-related
-handling of the local part during the verification is controlled by the router
-configuration (see the &%caseful_local_part%& generic router option).
-
-This facility could be used, for example, to add a spam score to local parts
-containing upper case letters. For example, using &$acl_m4$& to accumulate the
-spam score:
-.code
-warn  control = caseful_local_part
-      set acl_m4 = ${eval:\
-                     $acl_m4 + \
-                     ${if match{$local_part}{[A-Z]}{1}{0}}\
-                    }
-      control = caselower_local_part
-.endd
-Notice that we put back the lower cased version afterwards, assuming that
-is what is wanted for subsequent tests.
-
-
-.vitem &*control&~=&~cutthrough_delivery/*&<&'options'&>
-.cindex "&ACL;" "cutthrough routing"
-.cindex "cutthrough" "requesting"
-This option requests delivery be attempted while the item is being received.
-
-The option is usable in the RCPT ACL.
-If enabled for a message received via smtp and routed to an smtp transport,
-and only one transport, interface, destination host and port combination
-is used for all recipients of the message,
-then the delivery connection is made while the receiving connection is open
-and data is copied from one to the other.
-
-An attempt to set this option for any recipient but the first
-for a mail will be quietly ignored.
-If a recipient-verify callout
-(with use_sender)
-connection is subsequently
-requested in the same ACL it is held open and used for
-any subsequent recipients and the data,
-otherwise one is made after the initial RCPT ACL completes.
-
-Note that routers are used in verify mode,
-and cannot depend on content of received headers.
-Note also that headers cannot be
-modified by any of the post-data ACLs (DATA, MIME and DKIM).
-Headers may be modified by routers (subject to the above) and transports.
-The &'Received-By:'& header is generated as soon as the body reception starts,
-rather than the traditional time after the full message is received;
-this will affect the timestamp.
-
-All the usual ACLs are called; if one results in the message being
-rejected, all effort spent in delivery (including the costs on
-the ultimate destination) will be wasted.
-Note that in the case of data-time ACLs this includes the entire
-message body.
-
-Cutthrough delivery is not supported via transport-filters or when DKIM signing
-of outgoing messages is done, because it sends data to the ultimate destination
-before the entire message has been received from the source.
-It is not supported for messages received with the SMTP PRDR
-or CHUNKING
-options in use.
-
-Should the ultimate destination system positively accept or reject the mail,
-a corresponding indication is given to the source system and nothing is queued.
-If the item is successfully delivered in cutthrough mode
-the delivery log lines are tagged with ">>" rather than "=>" and appear
-before the acceptance "<=" line.
-
-If there is a temporary error the item is queued for later delivery in the
-usual fashion.
-This behaviour can be adjusted by appending the option &*defer=*&<&'value'&>
-to the control; the default value is &"spool"& and the alternate value
-&"pass"& copies an SMTP defer response from the target back to the initiator
-and does not queue the message.
-Note that this is independent of any recipient verify conditions in the ACL.
-
-Delivery in this mode avoids the generation of a bounce mail to a
-(possibly faked)
-sender when the destination system is doing content-scan based rejection.
-
-
-.vitem &*control&~=&~debug/*&<&'options'&>
-.cindex "&ACL;" "enabling debug logging"
-.cindex "debugging" "enabling from an ACL"
-This control turns on debug logging, almost as though Exim had been invoked
-with &`-d`&, with the output going to a new logfile in the usual logs directory,
-by default called &'debuglog'&.
-The filename can be adjusted with the &'tag'& option, which
-may access any variables already defined.  The logging may be adjusted with
-the &'opts'& option, which takes the same values as the &`-d`& command-line
-option.
-Logging started this way may be stopped, and the file removed,
-with the &'kill'& option.
-Some examples (which depend on variables that don't exist in all
-contexts):
-.code
-      control = debug
-      control = debug/tag=.$sender_host_address
-      control = debug/opts=+expand+acl
-      control = debug/tag=.$message_exim_id/opts=+expand
-      control = debug/kill
-.endd
-
-
-.vitem &*control&~=&~dkim_disable_verify*&
-.cindex "disable DKIM verify"
-.cindex "DKIM" "disable verify"
-This control turns off DKIM verification processing entirely.  For details on
-the operation and configuration of DKIM, see section &<<SECDKIM>>&.
-
-
-.vitem &*control&~=&~dmarc_disable_verify*&
-.cindex "disable DMARC verify"
-.cindex "DMARC" "disable verify"
-This control turns off DMARC verification processing entirely.  For details on
-the operation and configuration of DMARC, see section &<<SECDMARC>>&.
-
-
-.vitem &*control&~=&~dscp/*&<&'value'&>
-.cindex "&ACL;" "setting DSCP value"
-.cindex "DSCP" "inbound"
-This option causes the DSCP value associated with the socket for the inbound
-connection to be adjusted to a given value, given as one of a number of fixed
-strings or to numeric value.
-The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
-Common values include &`throughput`&, &`mincost`&, and on newer systems
-&`ef`&, &`af41`&, etc.  Numeric values may be in the range 0 to 0x3F.
-
-The outbound packets from Exim will be marked with this value in the header
-(for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
-that these values will have any effect, not be stripped by networking
-equipment, or do much of anything without cooperation with your Network
-Engineer and those of all network operators between the source and destination.
-
-
-.vitem &*control&~=&~enforce_sync*& &&&
-       &*control&~=&~no_enforce_sync*&
-.cindex "SMTP" "synchronization checking"
-.cindex "synchronization checking in SMTP"
-These controls make it possible to be selective about when SMTP synchronization
-is enforced. The global option &%smtp_enforce_sync%& specifies the initial
-state of the switch (it is true by default). See the description of this option
-in chapter &<<CHAPmainconfig>>& for details of SMTP synchronization checking.
-
-The effect of these two controls lasts for the remainder of the SMTP
-connection. They can appear in any ACL except the one for the non-SMTP
-messages. The most straightforward place to put them is in the ACL defined by
-&%acl_smtp_connect%&, which is run at the start of an incoming SMTP connection,
-before the first synchronization check. The expected use is to turn off the
-synchronization checks for badly-behaved hosts that you nevertheless need to
-work with.
-
-
-.vitem &*control&~=&~fakedefer/*&<&'message'&>
-.cindex "fake defer"
-.cindex "defer, fake"
-This control works in exactly the same way as &%fakereject%& (described below)
-except that it causes an SMTP 450 response after the message data instead of a
-550 response. You must take care when using &%fakedefer%& because it causes the
-messages to be duplicated when the sender retries. Therefore, you should not
-use &%fakedefer%& if the message is to be delivered normally.
-
-.vitem &*control&~=&~fakereject/*&<&'message'&>
-.cindex "fake rejection"
-.cindex "rejection, fake"
-This control is permitted only for the MAIL, RCPT, and DATA ACLs, in other
-words, only when an SMTP message is being received. If Exim accepts the
-message, instead the final 250 response, a 550 rejection message is sent.
-However, Exim proceeds to deliver the message as normal. The control applies
-only to the current message, not to any subsequent ones that may be received in
-the same SMTP connection.
-
-The text for the 550 response is taken from the &%control%& modifier. If no
-message is supplied, the following is used:
-.code
-550-Your message has been rejected but is being
-550-kept for evaluation.
-550-If it was a legitimate message, it may still be
-550 delivered to the target recipient(s).
-.endd
-This facility should be used with extreme caution.
-
-.vitem &*control&~=&~freeze*&
-.cindex "frozen messages" "forcing in ACL"
-This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
-other words, only when a message is being received. If the message is accepted,
-it is placed on Exim's queue and frozen. The control applies only to the
-current message, not to any subsequent ones that may be received in the same
-SMTP connection.
-
-This modifier can optionally be followed by &`/no_tell`&. If the global option
-&%freeze_tell%& is set, it is ignored for the current message (that is, nobody
-is told about the freezing), provided all the &*control=freeze*& modifiers that
-are obeyed for the current message have the &`/no_tell`& option.
-
-.vitem &*control&~=&~no_delay_flush*&
-.cindex "SMTP" "output flushing, disabling for delay"
-Exim normally flushes SMTP output before implementing a delay in an ACL, to
-avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
-use. This control, as long as it is encountered before the &%delay%& modifier,
-disables such output flushing.
-
-.vitem &*control&~=&~no_callout_flush*&
-.cindex "SMTP" "output flushing, disabling for callout"
-Exim normally flushes SMTP output before performing a callout in an ACL, to
-avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
-use. This control, as long as it is encountered before the &%verify%& condition
-that causes the callout, disables such output flushing.
-
-.vitem &*control&~=&~no_mbox_unspool*&
-This control is available when Exim is compiled with the content scanning
-extension. Content scanning may require a copy of the current message, or parts
-of it, to be written in &"mbox format"& to a spool file, for passing to a virus
-or spam scanner. Normally, such copies are deleted when they are no longer
-needed. If this control is set, the copies are not deleted. The control applies
-only to the current message, not to any subsequent ones that may be received in
-the same SMTP connection. It is provided for debugging purposes and is unlikely
-to be useful in production.
-
-.vitem &*control&~=&~no_multiline_responses*&
-.cindex "multiline responses, suppressing"
-This control is permitted for any ACL except the one for non-SMTP messages.
-It seems that there are broken clients in use that cannot handle multiline
-SMTP responses, despite the fact that RFC 821 defined them over 20 years ago.
-
-If this control is set, multiline SMTP responses from ACL rejections are
-suppressed. One way of doing this would have been to put out these responses as
-one long line. However, RFC 2821 specifies a maximum of 512 bytes per response
-(&"use multiline responses for more"& it says &-- ha!), and some of the
-responses might get close to that. So this facility, which is after all only a
-sop to broken clients, is implemented by doing two very easy things:
-
-.ilist
-Extra information that is normally output as part of a rejection caused by
-sender verification failure is omitted. Only the final line (typically &"sender
-verification failed"&) is sent.
-.next
-If a &%message%& modifier supplies a multiline response, only the first
-line is output.
-.endlist
-
-The setting of the switch can, of course, be made conditional on the
-calling host. Its effect lasts until the end of the SMTP connection.
-
-.vitem &*control&~=&~no_pipelining*&
-.cindex "PIPELINING" "suppressing advertising"
-This control turns off the advertising of the PIPELINING extension to SMTP in
-the current session. To be useful, it must be obeyed before Exim sends its
-response to an EHLO command. Therefore, it should normally appear in an ACL
-controlled by &%acl_smtp_connect%& or &%acl_smtp_helo%&. See also
-&%pipelining_advertise_hosts%&.
-
-.new
-.vitem &*control&~=&~queue/*&<&'options'&>* &&&
-       &*control&~=&~queue_only*&
-.oindex "&%queue%&"
-.oindex "&%queue_only%&"
-.cindex "queueing incoming messages"
-.cindex queueing "forcing in ACL"
-.cindex "first pass routing"
-This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
-other words, only when a message is being received. If the message is accepted,
-it is placed on Exim's queue and left there for delivery by a subsequent queue
-runner.
-If used with no options set,
-no immediate delivery process is started. In other words, it has the
-effect as the &%queue_only%& global option or &'-odq'& command-line option.
-
-If the &'first_pass_route'& option is given then
-the behaviour is like the command-line &'-oqds'& option;
-a delivery process is started which stops short of making
-any SMTP delivery.  The benefit is that the hints database will be updated for
-the message being waiting for a specific host, and a later queue run will be
-able to send all such messages on a single connection.
-
-The control only applies to the current message, not to any subsequent ones that
- may be received in the same SMTP connection.
-.wen
-
-.vitem &*control&~=&~submission/*&<&'options'&>
-.cindex "message" "submission"
-.cindex "submission mode"
-This control is permitted only for the MAIL, RCPT, and start of data ACLs (the
-latter is the one defined by &%acl_smtp_predata%&). Setting it tells Exim that
-the current message is a submission from a local MUA. In this case, Exim
-operates in &"submission mode"&, and applies certain fixups to the message if
-necessary. For example, it adds a &'Date:'& header line if one is not present.
-This control is not permitted in the &%acl_smtp_data%& ACL, because that is too
-late (the message has already been created).
-
-Chapter &<<CHAPmsgproc>>& describes the processing that Exim applies to
-messages. Section &<<SECTsubmodnon>>& covers the processing that happens in
-submission mode; the available options for this control are described there.
-The control applies only to the current message, not to any subsequent ones
-that may be received in the same SMTP connection.
-
-.vitem &*control&~=&~suppress_local_fixups*&
-.cindex "submission fixups, suppressing"
-This control applies to locally submitted (non TCP/IP) messages, and is the
-complement of &`control = submission`&. It disables the fixups that are
-normally applied to locally-submitted messages. Specifically:
-
-.ilist
-Any &'Sender:'& header line is left alone (in this respect, it is a
-dynamic version of &%local_sender_retain%&).
-.next
-No &'Message-ID:'&, &'From:'&, or &'Date:'& header lines are added.
-.next
-There is no check that &'From:'& corresponds to the actual sender.
-.endlist ilist
-
-This control may be useful when a remotely-originated message is accepted,
-passed to some scanning program, and then re-submitted for delivery. It can be
-used only in the &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
-and &%acl_not_smtp_start%& ACLs, because it has to be set before the message's
-data is read.
-
-&*Note:*& This control applies only to the current message, not to any others
-that are being submitted at the same time using &%-bs%& or &%-bS%&.
-
-.vitem &*control&~=&~utf8_downconvert*&
-This control enables conversion of UTF-8 in message addresses
-to a-label form.
-For details see section &<<SECTi18nMTA>>&.
-.endlist vlist
-
-
-.section "Summary of message fixup control" "SECTsummesfix"
-All four possibilities for message fixups can be specified:
-
-.ilist
-Locally submitted, fixups applied: the default.
-.next
-Locally submitted, no fixups applied: use
-&`control = suppress_local_fixups`&.
-.next
-Remotely submitted, no fixups applied: the default.
-.next
-Remotely submitted, fixups applied: use &`control = submission`&.
-.endlist
-
-
-
-.section "Adding header lines in ACLs" "SECTaddheadacl"
-.cindex "header lines" "adding in an ACL"
-.cindex "header lines" "position of added lines"
-.cindex "&%add_header%& ACL modifier"
-The &%add_header%& modifier can be used to add one or more extra header lines
-to an incoming message, as in this example:
-.code
-warn dnslists = sbl.spamhaus.org : \
-                dialup.mail-abuse.org
-     add_header = X-blacklisted-at: $dnslist_domain
-.endd
-The &%add_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
-MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
-receiving a message). The message must ultimately be accepted for
-&%add_header%& to have any significant effect. You can use &%add_header%& with
-any ACL verb, including &%deny%& (though this is potentially useful only in a
-RCPT ACL).
-
-Headers will not be added to the message if the modifier is used in
-DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
-
-Leading and trailing newlines are removed from
-the data for the &%add_header%& modifier; if it then
-contains one or more newlines that
-are not followed by a space or a tab, it is assumed to contain multiple header
-lines. Each one is checked for valid syntax; &`X-ACL-Warn:`& is added to the
-front of any line that is not a valid header line.
-
-Added header lines are accumulated during the MAIL, RCPT, and predata ACLs.
-They are added to the message before processing the DATA and MIME ACLs.
-However, if an identical header line is requested more than once, only one copy
-is actually added to the message. Further header lines may be accumulated
-during the DATA and MIME ACLs, after which they are added to the message, again
-with duplicates suppressed. Thus, it is possible to add two identical header
-lines to an SMTP message, but only if one is added before DATA and one after.
-In the case of non-SMTP messages, new headers are accumulated during the
-non-SMTP ACLs, and are added to the message after all the ACLs have run. If a
-message is rejected after DATA or by the non-SMTP ACL, all added header lines
-are included in the entry that is written to the reject log.
-
-.cindex "header lines" "added; visibility of"
-Header lines are not visible in string expansions
-of message headers
-until they are added to the
-message. It follows that header lines defined in the MAIL, RCPT, and predata
-ACLs are not visible until the DATA ACL and MIME ACLs are run. Similarly,
-header lines that are added by the DATA or MIME ACLs are not visible in those
-ACLs. Because of this restriction, you cannot use header lines as a way of
-passing data between (for example) the MAIL and RCPT ACLs. If you want to do
-this, you can use ACL variables, as described in section
-&<<SECTaclvariables>>&.
-
-The list of headers yet to be added is given by the &%$headers_added%& variable.
-
-The &%add_header%& modifier acts immediately as it is encountered during the
-processing of an ACL. Notice the difference between these two cases:
-.display
-&`accept add_header = ADDED: some text`&
-&`       `&<&'some condition'&>
-
-&`accept `&<&'some condition'&>
-&`       add_header = ADDED: some text`&
-.endd
-In the first case, the header line is always added, whether or not the
-condition is true. In the second case, the header line is added only if the
-condition is true. Multiple occurrences of &%add_header%& may occur in the same
-ACL statement. All those that are encountered before a condition fails are
-honoured.
-
-.cindex "&%warn%& ACL verb"
-For compatibility with previous versions of Exim, a &%message%& modifier for a
-&%warn%& verb acts in the same way as &%add_header%&, except that it takes
-effect only if all the conditions are true, even if it appears before some of
-them. Furthermore, only the last occurrence of &%message%& is honoured. This
-usage of &%message%& is now deprecated. If both &%add_header%& and &%message%&
-are present on a &%warn%& verb, both are processed according to their
-specifications.
-
-By default, new header lines are added to a message at the end of the existing
-header lines. However, you can specify that any particular header line should
-be added right at the start (before all the &'Received:'& lines), immediately
-after the first block of &'Received:'& lines, or immediately before any line
-that is not a &'Received:'& or &'Resent-something:'& header.
-
-This is done by specifying &":at_start:"&, &":after_received:"&, or
-&":at_start_rfc:"& (or, for completeness, &":at_end:"&) before the text of the
-header line, respectively. (Header text cannot start with a colon, as there has
-to be a header name first.) For example:
-.code
-warn add_header = \
-       :after_received:X-My-Header: something or other...
-.endd
-If more than one header line is supplied in a single &%add_header%& modifier,
-each one is treated independently and can therefore be placed differently. If
-you add more than one line at the start, or after the Received: block, they end
-up in reverse order.
-
-&*Warning*&: This facility currently applies only to header lines that are
-added in an ACL. It does NOT work for header lines that are added in a
-system filter or in a router or transport.
-
-
-
-.section "Removing header lines in ACLs" "SECTremoveheadacl"
-.cindex "header lines" "removing in an ACL"
-.cindex "header lines" "position of removed lines"
-.cindex "&%remove_header%& ACL modifier"
-The &%remove_header%& modifier can be used to remove one or more header lines
-from an incoming message, as in this example:
-.code
-warn   message        = Remove internal headers
-       remove_header  = x-route-mail1 : x-route-mail2
-.endd
-The &%remove_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
-MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
-receiving a message). The message must ultimately be accepted for
-&%remove_header%& to have any significant effect. You can use &%remove_header%&
-with any ACL verb, including &%deny%&, though this is really not useful for
-any verb that doesn't result in a delivered message.
-
-Headers will not be removed from the message if the modifier is used in
-DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
-
-More than one header can be removed at the same time by using a colon separated
-list of header names. The header matching is case insensitive. Wildcards are
-not permitted, nor is list expansion performed, so you cannot use hostlists to
-create a list of headers, however both connection and message variable expansion
-are performed (&%$acl_c_*%& and &%$acl_m_*%&), illustrated in this example:
-.code
-warn   hosts           = +internal_hosts
-       set acl_c_ihdrs = x-route-mail1 : x-route-mail2
-warn   message         = Remove internal headers
-       remove_header   = $acl_c_ihdrs
-.endd
-Header names for removal are accumulated during the MAIL, RCPT, and predata ACLs.
-Matching header lines are removed from the message before processing the DATA and MIME ACLs.
-If multiple header lines match, all are removed.
-There is no harm in attempting to remove the same header twice nor in removing
-a non-existent header. Further header lines to be removed may be accumulated
-during the DATA and MIME ACLs, after which they are removed from the message,
-if present. In the case of non-SMTP messages, headers to be removed are
-accumulated during the non-SMTP ACLs, and are removed from the message after
-all the ACLs have run. If a message is rejected after DATA or by the non-SMTP
-ACL, there really is no effect because there is no logging of what headers
-would have been removed.
-
-.cindex "header lines" "removed; visibility of"
-Header lines are not visible in string expansions until the DATA phase when it
-is received. Any header lines removed in the MAIL, RCPT, and predata ACLs are
-not visible in the DATA ACL and MIME ACLs. Similarly, header lines that are
-removed by the DATA or MIME ACLs are still visible in those ACLs. Because of
-this restriction, you cannot use header lines as a way of controlling data
-passed between (for example) the MAIL and RCPT ACLs. If you want to do this,
-you should instead use ACL variables, as described in section
-&<<SECTaclvariables>>&.
-
-The &%remove_header%& modifier acts immediately as it is encountered during the
-processing of an ACL. Notice the difference between these two cases:
-.display
-&`accept remove_header = X-Internal`&
-&`       `&<&'some condition'&>
-
-&`accept `&<&'some condition'&>
-&`       remove_header = X-Internal`&
-.endd
-In the first case, the header line is always removed, whether or not the
-condition is true. In the second case, the header line is removed only if the
-condition is true. Multiple occurrences of &%remove_header%& may occur in the
-same ACL statement. All those that are encountered before a condition fails
-are honoured.
-
-&*Warning*&: This facility currently applies only to header lines that are
-present during ACL processing. It does NOT remove header lines that are added
-in a system filter or in a router or transport.
-
-
-
-
-.section "ACL conditions" "SECTaclconditions"
-.cindex "&ACL;" "conditions; list of"
-Some of the conditions listed in this section are available only when Exim is
-compiled with the content-scanning extension. They are included here briefly
-for completeness. More detailed descriptions can be found in the discussion on
-content scanning in chapter &<<CHAPexiscan>>&.
-
-Not all conditions are relevant in all circumstances. For example, testing
-senders and recipients does not make sense in an ACL that is being run as the
-result of the arrival of an ETRN command, and checks on message headers can be
-done only in the ACLs specified by &%acl_smtp_data%& and &%acl_not_smtp%&. You
-can use the same condition (with different parameters) more than once in the
-same ACL statement. This provides a way of specifying an &"and"& conjunction.
-The conditions are as follows:
-
-
-.vlist
-.vitem &*acl&~=&~*&<&'name&~of&~acl&~or&~ACL&~string&~or&~file&~name&~'&>
-.cindex "&ACL;" "nested"
-.cindex "&ACL;" "indirect"
-.cindex "&ACL;" "arguments"
-.cindex "&%acl%& ACL condition"
-The possible values of the argument are the same as for the
-&%acl_smtp_%&&'xxx'& options. The named or inline ACL is run. If it returns
-&"accept"& the condition is true; if it returns &"deny"& the condition is
-false. If it returns &"defer"&, the current ACL returns &"defer"& unless the
-condition is on a &%warn%& verb. In that case, a &"defer"& return makes the
-condition false. This means that further processing of the &%warn%& verb
-ceases, but processing of the ACL continues.
-
-If the argument is a named ACL, up to nine space-separated optional values
-can be appended; they appear within the called ACL in $acl_arg1 to $acl_arg9,
-and $acl_narg is set to the count of values.
-Previous values of these variables are restored after the call returns.
-The name and values are expanded separately.
-Note that spaces in complex expansions which are used as arguments
-will act as argument separators.
-
-If the nested &%acl%& returns &"drop"& and the outer condition denies access,
-the connection is dropped. If it returns &"discard"&, the verb must be
-&%accept%& or &%discard%&, and the action is taken immediately &-- no further
-conditions are tested.
-
-ACLs may be nested up to 20 deep; the limit exists purely to catch runaway
-loops. This condition allows you to use different ACLs in different
-circumstances. For example, different ACLs can be used to handle RCPT commands
-for different local users or different local domains.
-
-.vitem &*authenticated&~=&~*&<&'string&~list'&>
-.cindex "&%authenticated%& ACL condition"
-.cindex "authentication" "ACL checking"
-.cindex "&ACL;" "testing for authentication"
-If the SMTP connection is not authenticated, the condition is false. Otherwise,
-the name of the authenticator is tested against the list. To test for
-authentication by any authenticator, you can set
-.code
-authenticated = *
-.endd
-
-.vitem &*condition&~=&~*&<&'string'&>
-.cindex "&%condition%& ACL condition"
-.cindex "customizing" "ACL condition"
-.cindex "&ACL;" "customized test"
-.cindex "&ACL;" "testing, customized"
-This feature allows you to make up custom conditions. If the result of
-expanding the string is an empty string, the number zero, or one of the strings
-&"no"& or &"false"&, the condition is false. If the result is any non-zero
-number, or one of the strings &"yes"& or &"true"&, the condition is true. For
-any other value, some error is assumed to have occurred, and the ACL returns
-&"defer"&. However, if the expansion is forced to fail, the condition is
-ignored. The effect is to treat it as true, whether it is positive or
-negative.
-
-.vitem &*decode&~=&~*&<&'location'&>
-.cindex "&%decode%& ACL condition"
-This condition is available only when Exim is compiled with the
-content-scanning extension, and it is allowed only in the ACL defined by
-&%acl_smtp_mime%&. It causes the current MIME part to be decoded into a file.
-If all goes well, the condition is true. It is false only if there are
-problems such as a syntax error or a memory shortage. For more details, see
-chapter &<<CHAPexiscan>>&.
-
-.vitem &*dnslists&~=&~*&<&'list&~of&~domain&~names&~and&~other&~data'&>
-.cindex "&%dnslists%& ACL condition"
-.cindex "DNS list" "in ACL"
-.cindex "black list (DNS)"
-.cindex "&ACL;" "testing a DNS list"
-This condition checks for entries in DNS black lists. These are also known as
-&"RBL lists"&, after the original Realtime Blackhole List, but note that the
-use of the lists at &'mail-abuse.org'& now carries a charge. There are too many
-different variants of this condition to describe briefly here. See sections
-&<<SECTmorednslists>>&&--&<<SECTmorednslistslast>>& for details.
-
-.vitem &*domains&~=&~*&<&'domain&~list'&>
-.cindex "&%domains%& ACL condition"
-.cindex "domain" "ACL checking"
-.cindex "&ACL;" "testing a recipient domain"
-.vindex "&$domain_data$&"
-This condition is relevant only after a RCPT command. It checks that the domain
-of the recipient address is in the domain list. If percent-hack processing is
-enabled, it is done before this test is done. If the check succeeds with a
-lookup, the result of the lookup is placed in &$domain_data$& until the next
-&%domains%& test.
-
-&*Note carefully*& (because many people seem to fall foul of this): you cannot
-use &%domains%& in a DATA ACL.
-
-
-.vitem &*encrypted&~=&~*&<&'string&~list'&>
-.cindex "&%encrypted%& ACL condition"
-.cindex "encryption" "checking in an ACL"
-.cindex "&ACL;" "testing for encryption"
-If the SMTP connection is not encrypted, the condition is false. Otherwise, the
-name of the cipher suite in use is tested against the list. To test for
-encryption without testing for any specific cipher suite(s), set
-.code
-encrypted = *
-.endd
-
-
-.vitem &*hosts&~=&~*&<&'host&~list'&>
-.cindex "&%hosts%& ACL condition"
-.cindex "host" "ACL checking"
-.cindex "&ACL;" "testing the client host"
-This condition tests that the calling host matches the host list. If you have
-name lookups or wildcarded host names and IP addresses in the same host list,
-you should normally put the IP addresses first. For example, you could have:
-.code
-accept hosts = 10.9.8.7 : dbm;/etc/friendly/hosts
-.endd
-The lookup in this example uses the host name for its key. This is implied by
-the lookup type &"dbm"&. (For a host address lookup you would use &"net-dbm"&
-and it wouldn't matter which way round you had these two items.)
-
-The reason for the problem with host names lies in the left-to-right way that
-Exim processes lists. It can test IP addresses without doing any DNS lookups,
-but when it reaches an item that requires a host name, it fails if it cannot
-find a host name to compare with the pattern. If the above list is given in the
-opposite order, the &%accept%& statement fails for a host whose name cannot be
-found, even if its IP address is 10.9.8.7.
-
-If you really do want to do the name check first, and still recognize the IP
-address even if the name lookup fails, you can rewrite the ACL like this:
-.code
-accept hosts = dbm;/etc/friendly/hosts
-accept hosts = 10.9.8.7
-.endd
-The default action on failing to find the host name is to assume that the host
-is not in the list, so the first &%accept%& statement fails. The second
-statement can then check the IP address.
-
-.vindex "&$host_data$&"
-If a &%hosts%& condition is satisfied by means of a lookup, the result
-of the lookup is made available in the &$host_data$& variable. This
-allows you, for example, to set up a statement like this:
-.code
-deny  hosts = net-lsearch;/some/file
-message = $host_data
-.endd
-which gives a custom error message for each denied host.
-
-.vitem &*local_parts&~=&~*&<&'local&~part&~list'&>
-.cindex "&%local_parts%& ACL condition"
-.cindex "local part" "ACL checking"
-.cindex "&ACL;" "testing a local part"
-.vindex "&$local_part_data$&"
-This condition is relevant only after a RCPT command. It checks that the local
-part of the recipient address is in the list. If percent-hack processing is
-enabled, it is done before this test. If the check succeeds with a lookup, the
-result of the lookup is placed in &$local_part_data$&, which remains set until
-the next &%local_parts%& test.
-
-.vitem &*malware&~=&~*&<&'option'&>
-.cindex "&%malware%& ACL condition"
-.cindex "&ACL;" "virus scanning"
-.cindex "&ACL;" "scanning for viruses"
-This condition is available only when Exim is compiled with the
-content-scanning extension
-and only after a DATA command.
-It causes the incoming message to be scanned for
-viruses. For details, see chapter &<<CHAPexiscan>>&.
-
-.vitem &*mime_regex&~=&~*&<&'list&~of&~regular&~expressions'&>
-.cindex "&%mime_regex%& ACL condition"
-.cindex "&ACL;" "testing by regex matching"
-This condition is available only when Exim is compiled with the
-content-scanning extension, and it is allowed only in the ACL defined by
-&%acl_smtp_mime%&. It causes the current MIME part to be scanned for a match
-with any of the regular expressions. For details, see chapter
-&<<CHAPexiscan>>&.
-
-.vitem &*ratelimit&~=&~*&<&'parameters'&>
-.cindex "rate limiting"
-This condition can be used to limit the rate at which a user or host submits
-messages. Details are given in section &<<SECTratelimiting>>&.
-
-.vitem &*recipients&~=&~*&<&'address&~list'&>
-.cindex "&%recipients%& ACL condition"
-.cindex "recipient" "ACL checking"
-.cindex "&ACL;" "testing a recipient"
-This condition is relevant only after a RCPT command. It checks the entire
-recipient address against a list of recipients.
-
-.vitem &*regex&~=&~*&<&'list&~of&~regular&~expressions'&>
-.cindex "&%regex%& ACL condition"
-.cindex "&ACL;" "testing by regex matching"
-This condition is available only when Exim is compiled with the
-content-scanning extension, and is available only in the DATA, MIME, and
-non-SMTP ACLs. It causes the incoming message to be scanned for a match with
-any of the regular expressions. For details, see chapter &<<CHAPexiscan>>&.
-
-.vitem &*sender_domains&~=&~*&<&'domain&~list'&>
-.cindex "&%sender_domains%& ACL condition"
-.cindex "sender" "ACL checking"
-.cindex "&ACL;" "testing a sender domain"
-.vindex "&$domain$&"
-.vindex "&$sender_address_domain$&"
-This condition tests the domain of the sender of the message against the given
-domain list. &*Note*&: The domain of the sender address is in
-&$sender_address_domain$&. It is &'not'& put in &$domain$& during the testing
-of this condition. This is an exception to the general rule for testing domain
-lists. It is done this way so that, if this condition is used in an ACL for a
-RCPT command, the recipient's domain (which is in &$domain$&) can be used to
-influence the sender checking.
-
-&*Warning*&: It is a bad idea to use this condition on its own as a control on
-relaying, because sender addresses are easily, and commonly, forged.
-
-.vitem &*senders&~=&~*&<&'address&~list'&>
-.cindex "&%senders%& ACL condition"
-.cindex "sender" "ACL checking"
-.cindex "&ACL;" "testing a sender"
-This condition tests the sender of the message against the given list. To test
-for a bounce message, which has an empty sender, set
-.code
-senders = :
-.endd
-&*Warning*&: It is a bad idea to use this condition on its own as a control on
-relaying, because sender addresses are easily, and commonly, forged.
-
-.vitem &*spam&~=&~*&<&'username'&>
-.cindex "&%spam%& ACL condition"
-.cindex "&ACL;" "scanning for spam"
-This condition is available only when Exim is compiled with the
-content-scanning extension. It causes the incoming message to be scanned by
-SpamAssassin. For details, see chapter &<<CHAPexiscan>>&.
-
-.vitem &*verify&~=&~certificate*&
-.cindex "&%verify%& ACL condition"
-.cindex "TLS" "client certificate verification"
-.cindex "certificate" "verification of client"
-.cindex "&ACL;" "certificate verification"
-.cindex "&ACL;" "testing a TLS certificate"
-This condition is true in an SMTP session if the session is encrypted, and a
-certificate was received from the client, and the certificate was verified. The
-server requests a certificate only if the client matches &%tls_verify_hosts%&
-or &%tls_try_verify_hosts%& (see chapter &<<CHAPTLS>>&).
-
-.vitem &*verify&~=&~csa*&
-.cindex "CSA verification"
-This condition checks whether the sending host (the client) is authorized to
-send email. Details of how this works are given in section
-&<<SECTverifyCSA>>&.
-
-.vitem &*verify&~=&~header_names_ascii*&
-.cindex "&%verify%& ACL condition"
-.cindex "&ACL;" "verifying header names only ASCII"
-.cindex "header lines" "verifying header names only ASCII"
-.cindex "verifying" "header names only ASCII"
-This condition is relevant only in an ACL that is run after a message has been
-received, that is, in an ACL specified by &%acl_smtp_data%& or
-&%acl_not_smtp%&.  It checks all header names (not the content) to make sure
-there are no non-ASCII characters, also excluding control characters.  The
-allowable characters are decimal ASCII values 33 through 126.
-
-Exim itself will handle headers with non-ASCII characters, but it can cause
-problems for downstream applications, so this option will allow their
-detection and rejection in the DATA ACL's.
-
-.vitem &*verify&~=&~header_sender/*&<&'options'&>
-.cindex "&%verify%& ACL condition"
-.cindex "&ACL;" "verifying sender in the header"
-.cindex "header lines" "verifying the sender in"
-.cindex "sender" "verifying in header"
-.cindex "verifying" "sender in header"
-This condition is relevant only in an ACL that is run after a message has been
-received, that is, in an ACL specified by &%acl_smtp_data%& or
-&%acl_not_smtp%&. It checks that there is a verifiable address in at least one
-of the &'Sender:'&, &'Reply-To:'&, or &'From:'& header lines. Such an address
-is loosely thought of as a &"sender"& address (hence the name of the test).
-However, an address that appears in one of these headers need not be an address
-that accepts bounce messages; only sender addresses in envelopes are required
-to accept bounces. Therefore, if you use the callout option on this check, you
-might want to arrange for a non-empty address in the MAIL command.
-
-Details of address verification and the options are given later, starting at
-section &<<SECTaddressverification>>& (callouts are described in section
-&<<SECTcallver>>&). You can combine this condition with the &%senders%&
-condition to restrict it to bounce messages only:
-.code
-deny    senders = :
-        message = A valid sender header is required for bounces
-       !verify  = header_sender
-.endd
-
-.vitem &*verify&~=&~header_syntax*&
-.cindex "&%verify%& ACL condition"
-.cindex "&ACL;" "verifying header syntax"
-.cindex "header lines" "verifying syntax"
-.cindex "verifying" "header syntax"
-This condition is relevant only in an ACL that is run after a message has been
-received, that is, in an ACL specified by &%acl_smtp_data%& or
-&%acl_not_smtp%&. It checks the syntax of all header lines that can contain
-lists of addresses (&'Sender:'&, &'From:'&, &'Reply-To:'&, &'To:'&, &'Cc:'&,
-and &'Bcc:'&), returning true if there are no problems.
-Unqualified addresses (local parts without domains) are
-permitted only in locally generated messages and from hosts that match
-&%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
-appropriate.
-
-Note that this condition is a syntax check only. However, a common spamming
-ploy used to be to send syntactically invalid headers such as
-.code
-To: @
-.endd
-and this condition can be used to reject such messages, though they are not as
-common as they used to be.
-
-.vitem &*verify&~=&~helo*&
-.cindex "&%verify%& ACL condition"
-.cindex "&ACL;" "verifying HELO/EHLO"
-.cindex "HELO" "verifying"
-.cindex "EHLO" "verifying"
-.cindex "verifying" "EHLO"
-.cindex "verifying" "HELO"
-This condition is true if a HELO or EHLO command has been received from the
-client host, and its contents have been verified. If there has been no previous
-attempt to verify the HELO/EHLO contents, it is carried out when this
-condition is encountered. See the description of the &%helo_verify_hosts%& and
-&%helo_try_verify_hosts%& options for details of how to request verification
-independently of this condition, and for detail of the verification.
-
-For SMTP input that does not come over TCP/IP (the &%-bs%& command line
-option), this condition is always true.
-
-
-.vitem &*verify&~=&~not_blind/*&<&'options'&>
-.cindex "verifying" "not blind"
-.cindex "bcc recipients, verifying none"
-This condition checks that there are no blind (bcc) recipients in the message.
-Every envelope recipient must appear either in a &'To:'& header line or in a
-&'Cc:'& header line for this condition to be true. Local parts are checked
-case-sensitively; domains are checked case-insensitively. If &'Resent-To:'& or
-&'Resent-Cc:'& header lines exist, they are also checked. This condition can be
-used only in a DATA or non-SMTP ACL.
-
-There is one possible option, &`case_insensitive`&.  If this is present then
-local parts are checked case-insensitively.
-
-There are, of course, many legitimate messages that make use of blind (bcc)
-recipients. This check should not be used on its own for blocking messages.
-
-
-.vitem &*verify&~=&~recipient/*&<&'options'&>
-.cindex "&%verify%& ACL condition"
-.cindex "&ACL;" "verifying recipient"
-.cindex "recipient" "verifying"
-.cindex "verifying" "recipient"
-.vindex "&$address_data$&"
-This condition is relevant only after a RCPT command. It verifies the current
-recipient. Details of address verification are given later, starting at section
-&<<SECTaddressverification>>&. After a recipient has been verified, the value
-of &$address_data$& is the last value that was set while routing the address.
-This applies even if the verification fails. When an address that is being
-verified is redirected to a single address, verification continues with the new
-address, and in that case, the subsequent value of &$address_data$& is the
-value for the child address.
-
-.vitem &*verify&~=&~reverse_host_lookup/*&<&'options'&>
-.cindex "&%verify%& ACL condition"
-.cindex "&ACL;" "verifying host reverse lookup"
-.cindex "host" "verifying reverse lookup"
-This condition ensures that a verified host name has been looked up from the IP
-address of the client host. (This may have happened already if the host name
-was needed for checking a host list, or if the host matched &%host_lookup%&.)
-Verification ensures that the host name obtained from a reverse DNS lookup, or
-one of its aliases, does, when it is itself looked up in the DNS, yield the
-original IP address.
-
-There is one possible option, &`defer_ok`&.  If this is present and a
-DNS operation returns a temporary error, the verify condition succeeds.
-
-If this condition is used for a locally generated message (that is, when there
-is no client host involved), it always succeeds.
-
-.vitem &*verify&~=&~sender/*&<&'options'&>
-.cindex "&%verify%& ACL condition"
-.cindex "&ACL;" "verifying sender"
-.cindex "sender" "verifying"
-.cindex "verifying" "sender"
-This condition is relevant only after a MAIL or RCPT command, or after a
-message has been received (the &%acl_smtp_data%& or &%acl_not_smtp%& ACLs). If
-the message's sender is empty (that is, this is a bounce message), the
-condition is true. Otherwise, the sender address is verified.
-
-.vindex "&$address_data$&"
-.vindex "&$sender_address_data$&"
-If there is data in the &$address_data$& variable at the end of routing, its
-value is placed in &$sender_address_data$& at the end of verification. This
-value can be used in subsequent conditions and modifiers in the same ACL
-statement. It does not persist after the end of the current statement. If you
-want to preserve the value for longer, you can save it in an ACL variable.
-
-Details of verification are given later, starting at section
-&<<SECTaddressverification>>&. Exim caches the result of sender verification,
-to avoid doing it more than once per message.
-
-.vitem &*verify&~=&~sender=*&<&'address'&>&*/*&<&'options'&>
-.cindex "&%verify%& ACL condition"
-This is a variation of the previous option, in which a modified address is
-verified as a sender.
-
-Note that '/' is legal in local-parts; if the address may have such
-(eg. is generated from the received message)
-they must be protected from the options parsing by doubling:
-.code
-verify = sender=${sg{${address:$h_sender:}}{/}{//}}
-.endd
-.endlist
-
-
-
-.section "Using DNS lists" "SECTmorednslists"
-.cindex "DNS list" "in ACL"
-.cindex "black list (DNS)"
-.cindex "&ACL;" "testing a DNS list"
-In its simplest form, the &%dnslists%& condition tests whether the calling host
-is on at least one of a number of DNS lists by looking up the inverted IP
-address in one or more DNS domains. (Note that DNS list domains are not mail
-domains, so the &`+`& syntax for named lists doesn't work - it is used for
-special options instead.) For example, if the calling host's IP
-address is 192.168.62.43, and the ACL statement is
-.code
-deny dnslists = blackholes.mail-abuse.org : \
-                dialups.mail-abuse.org
-.endd
-the following records are looked up:
-.code
-43.62.168.192.blackholes.mail-abuse.org
-43.62.168.192.dialups.mail-abuse.org
-.endd
-As soon as Exim finds an existing DNS record, processing of the list stops.
-Thus, multiple entries on the list provide an &"or"& conjunction. If you want
-to test that a host is on more than one list (an &"and"& conjunction), you can
-use two separate conditions:
-.code
-deny dnslists = blackholes.mail-abuse.org
-     dnslists = dialups.mail-abuse.org
-.endd
-If a DNS lookup times out or otherwise fails to give a decisive answer, Exim
-behaves as if the host does not match the list item, that is, as if the DNS
-record does not exist. If there are further items in the DNS list, they are
-processed.
-
-This is usually the required action when &%dnslists%& is used with &%deny%&
-(which is the most common usage), because it prevents a DNS failure from
-blocking mail. However, you can change this behaviour by putting one of the
-following special items in the list:
-.display
-&`+include_unknown `&   behave as if the item is on the list
-&`+exclude_unknown `&   behave as if the item is not on the list (default)
-&`+defer_unknown   `&   give a temporary error
-.endd
-.cindex "&`+include_unknown`&"
-.cindex "&`+exclude_unknown`&"
-.cindex "&`+defer_unknown`&"
-Each of these applies to any subsequent items on the list. For example:
-.code
-deny dnslists = +defer_unknown : foo.bar.example
-.endd
-Testing the list of domains stops as soon as a match is found. If you want to
-warn for one list and block for another, you can use two different statements:
-.code
-deny  dnslists = blackholes.mail-abuse.org
-warn  message  = X-Warn: sending host is on dialups list
-      dnslists = dialups.mail-abuse.org
-.endd
-.cindex caching "of dns lookup"
-.cindex DNS TTL
-DNS list lookups are cached by Exim for the duration of the SMTP session
-(but limited by the DNS return TTL value),
-so a lookup based on the IP address is done at most once for any incoming
-connection (assuming long-enough TTL).
-Exim does not share information between multiple incoming
-connections (but your local name server cache should be active).
-
-There are a number of DNS lists to choose from, some commercial, some free,
-or free for small deployments.  An overview can be found at
-&url(https://en.wikipedia.org/wiki/Comparison_of_DNS_blacklists).
-
-
-
-.section "Specifying the IP address for a DNS list lookup" "SECID201"
-.cindex "DNS list" "keyed by explicit IP address"
-By default, the IP address that is used in a DNS list lookup is the IP address
-of the calling host. However, you can specify another IP address by listing it
-after the domain name, introduced by a slash. For example:
-.code
-deny dnslists = black.list.tld/192.168.1.2
-.endd
-This feature is not very helpful with explicit IP addresses; it is intended for
-use with IP addresses that are looked up, for example, the IP addresses of the
-MX hosts or nameservers of an email sender address. For an example, see section
-&<<SECTmulkeyfor>>& below.
-
-
-
-
-.section "DNS lists keyed on domain names" "SECID202"
-.cindex "DNS list" "keyed by domain name"
-There are some lists that are keyed on domain names rather than inverted IP
-addresses (see, e.g., the &'domain based zones'& link at
-&url(http://www.rfc-ignorant.org/)). No reversing of components is used
-with these lists. You can change the name that is looked up in a DNS list by
-listing it after the domain name, introduced by a slash. For example,
-.code
-deny  message  = Sender's domain is listed at $dnslist_domain
-      dnslists = dsn.rfc-ignorant.org/$sender_address_domain
-.endd
-This particular example is useful only in ACLs that are obeyed after the
-RCPT or DATA commands, when a sender address is available. If (for
-example) the message's sender is &'user@tld.example'& the name that is looked
-up by this example is
-.code
-tld.example.dsn.rfc-ignorant.org
-.endd
-A single &%dnslists%& condition can contain entries for both names and IP
-addresses. For example:
-.code
-deny dnslists = sbl.spamhaus.org : \
-                dsn.rfc-ignorant.org/$sender_address_domain
-.endd
-The first item checks the sending host's IP address; the second checks a domain
-name. The whole condition is true if either of the DNS lookups succeeds.
-
-
-
-
-.section "Multiple explicit keys for a DNS list" "SECTmulkeyfor"
-.cindex "DNS list" "multiple keys for"
-The syntax described above for looking up explicitly-defined values (either
-names or IP addresses) in a DNS blacklist is a simplification. After the domain
-name for the DNS list, what follows the slash can in fact be a list of items.
-As with all lists in Exim, the default separator is a colon. However, because
-this is a sublist within the list of DNS blacklist domains, it is necessary
-either to double the separators like this:
-.code
-dnslists = black.list.tld/name.1::name.2
-.endd
-or to change the separator character, like this:
-.code
-dnslists = black.list.tld/<;name.1;name.2
-.endd
-If an item in the list is an IP address, it is inverted before the DNS
-blacklist domain is appended. If it is not an IP address, no inversion
-occurs. Consider this condition:
-.code
-dnslists = black.list.tld/<;192.168.1.2;a.domain
-.endd
-The DNS lookups that occur are:
-.code
-2.1.168.192.black.list.tld
-a.domain.black.list.tld
-.endd
-Once a DNS record has been found (that matches a specific IP return
-address, if specified &-- see section &<<SECTaddmatcon>>&), no further lookups
-are done. If there is a temporary DNS error, the rest of the sublist of domains
-or IP addresses is tried. A temporary error for the whole dnslists item occurs
-only if no other DNS lookup in this sublist succeeds. In other words, a
-successful lookup for any of the items in the sublist overrides a temporary
-error for a previous item.
-
-The ability to supply a list of items after the slash is in some sense just a
-syntactic convenience. These two examples have the same effect:
-.code
-dnslists = black.list.tld/a.domain : black.list.tld/b.domain
-dnslists = black.list.tld/a.domain::b.domain
-.endd
-However, when the data for the list is obtained from a lookup, the second form
-is usually much more convenient. Consider this example:
-.code
-deny message  = The mail servers for the domain \
-                $sender_address_domain \
-                are listed at $dnslist_domain ($dnslist_value); \
-                see $dnslist_text.
-     dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
-                                   ${lookup dnsdb {>|mxh=\
-                                   $sender_address_domain} }} }
-.endd
-Note the use of &`>|`& in the dnsdb lookup to specify the separator for
-multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
-and the outer dnsdb lookup finds the IP addresses for these hosts. The result
-of expanding the condition might be something like this:
-.code
-dnslists = sbl.spamhaus.org/<|192.168.2.3|192.168.5.6|...
-.endd
-Thus, this example checks whether or not the IP addresses of the sender
-domain's mail servers are on the Spamhaus black list.
-
-The key that was used for a successful DNS list lookup is put into the variable
-&$dnslist_matched$& (see section &<<SECID204>>&).
-
-
-
-
-.section "Data returned by DNS lists" "SECID203"
-.cindex "DNS list" "data returned from"
-DNS lists are constructed using address records in the DNS. The original RBL
-just used the address 127.0.0.1 on the right hand side of each record, but the
-RBL+ list and some other lists use a number of values with different meanings.
-The values used on the RBL+ list are:
-.display
-127.1.0.1  RBL
-127.1.0.2  DUL
-127.1.0.3  DUL and RBL
-127.1.0.4  RSS
-127.1.0.5  RSS and RBL
-127.1.0.6  RSS and DUL
-127.1.0.7  RSS and DUL and RBL
-.endd
-Section &<<SECTaddmatcon>>& below describes how you can distinguish between
-different values. Some DNS lists may return more than one address record;
-see section &<<SECThanmuldnsrec>>& for details of how they are checked.
-
-
-.section "Variables set from DNS lists" "SECID204"
-.cindex "expansion" "variables, set from DNS list"
-.cindex "DNS list" "variables set from"
-.vindex "&$dnslist_domain$&"
-.vindex "&$dnslist_matched$&"
-.vindex "&$dnslist_text$&"
-.vindex "&$dnslist_value$&"
-When an entry is found in a DNS list, the variable &$dnslist_domain$& contains
-the name of the overall domain that matched (for example,
-&`spamhaus.example`&), &$dnslist_matched$& contains the key within that domain
-(for example, &`192.168.5.3`&), and &$dnslist_value$& contains the data from
-the DNS record. When the key is an IP address, it is not reversed in
-&$dnslist_matched$& (though it is, of course, in the actual lookup). In simple
-cases, for example:
-.code
-deny dnslists = spamhaus.example
-.endd
-the key is also available in another variable (in this case,
-&$sender_host_address$&). In more complicated cases, however, this is not true.
-For example, using a data lookup (as described in section &<<SECTmulkeyfor>>&)
-might generate a dnslists lookup like this:
-.code
-deny dnslists = spamhaus.example/<|192.168.1.2|192.168.6.7|...
-.endd
-If this condition succeeds, the value in &$dnslist_matched$& might be
-&`192.168.6.7`& (for example).
-
-If more than one address record is returned by the DNS lookup, all the IP
-addresses are included in &$dnslist_value$&, separated by commas and spaces.
-The variable &$dnslist_text$& contains the contents of any associated TXT
-record. For lists such as RBL+ the TXT record for a merged entry is often not
-very meaningful. See section &<<SECTmordetinf>>& for a way of obtaining more
-information.
-
-You can use the DNS list variables in &%message%& or &%log_message%& modifiers
-&-- although these appear before the condition in the ACL, they are not
-expanded until after it has failed. For example:
-.code
-deny    hosts = !+local_networks
-        message = $sender_host_address is listed \
-                  at $dnslist_domain
-        dnslists = rbl-plus.mail-abuse.example
-.endd
-
-
-
-.section "Additional matching conditions for DNS lists" "SECTaddmatcon"
-.cindex "DNS list" "matching specific returned data"
-You can add an equals sign and an IP address after a &%dnslists%& domain name
-in order to restrict its action to DNS records with a matching right hand side.
-For example,
-.code
-deny dnslists = rblplus.mail-abuse.org=127.0.0.2
-.endd
-rejects only those hosts that yield 127.0.0.2. Without this additional data,
-any address record is considered to be a match. For the moment, we assume
-that the DNS lookup returns just one record. Section &<<SECThanmuldnsrec>>&
-describes how multiple records are handled.
-
-More than one IP address may be given for checking, using a comma as a
-separator. These are alternatives &-- if any one of them matches, the
-&%dnslists%& condition is true. For example:
-.code
-deny  dnslists = a.b.c=127.0.0.2,127.0.0.3
-.endd
-If you want to specify a constraining address list and also specify names or IP
-addresses to be looked up, the constraining address list must be specified
-first. For example:
-.code
-deny dnslists = dsn.rfc-ignorant.org\
-                =127.0.0.2/$sender_address_domain
-.endd
-
-If the character &`&&`& is used instead of &`=`&, the comparison for each
-listed IP address is done by a bitwise &"and"& instead of by an equality test.
-In other words, the listed addresses are used as bit masks. The comparison is
-true if all the bits in the mask are present in the address that is being
-tested. For example:
-.code
-dnslists = a.b.c&0.0.0.3
-.endd
-matches if the address is &'x.x.x.'&3, &'x.x.x.'&7, &'x.x.x.'&11, etc. If you
-want to test whether one bit or another bit is present (as opposed to both
-being present), you must use multiple values. For example:
-.code
-dnslists = a.b.c&0.0.0.1,0.0.0.2
-.endd
-matches if the final component of the address is an odd number or two times
-an odd number.
-
-
-
-.section "Negated DNS matching conditions" "SECID205"
-You can supply a negative list of IP addresses as part of a &%dnslists%&
-condition. Whereas
-.code
-deny  dnslists = a.b.c=127.0.0.2,127.0.0.3
-.endd
-means &"deny if the host is in the black list at the domain &'a.b.c'& and the
-IP address yielded by the list is either 127.0.0.2 or 127.0.0.3"&,
-.code
-deny  dnslists = a.b.c!=127.0.0.2,127.0.0.3
-.endd
-means &"deny if the host is in the black list at the domain &'a.b.c'& and the
-IP address yielded by the list is not 127.0.0.2 and not 127.0.0.3"&. In other
-words, the result of the test is inverted if an exclamation mark appears before
-the &`=`& (or the &`&&`&) sign.
-
-&*Note*&: This kind of negation is not the same as negation in a domain,
-host, or address list (which is why the syntax is different).
-
-If you are using just one list, the negation syntax does not gain you much. The
-previous example is precisely equivalent to
-.code
-deny  dnslists = a.b.c
-     !dnslists = a.b.c=127.0.0.2,127.0.0.3
-.endd
-However, if you are using multiple lists, the negation syntax is clearer.
-Consider this example:
-.code
-deny  dnslists = sbl.spamhaus.org : \
-                 list.dsbl.org : \
-                 dnsbl.njabl.org!=127.0.0.3 : \
-                 relays.ordb.org
-.endd
-Using only positive lists, this would have to be:
-.code
-deny  dnslists = sbl.spamhaus.org : \
-                 list.dsbl.org
-deny  dnslists = dnsbl.njabl.org
-     !dnslists = dnsbl.njabl.org=127.0.0.3
-deny  dnslists = relays.ordb.org
-.endd
-which is less clear, and harder to maintain.
-
-
-
-
-.section "Handling multiple DNS records from a DNS list" "SECThanmuldnsrec"
-A DNS lookup for a &%dnslists%& condition may return more than one DNS record,
-thereby providing more than one IP address. When an item in a &%dnslists%& list
-is followed by &`=`& or &`&&`& and a list of IP addresses, in order to restrict
-the match to specific results from the DNS lookup, there are two ways in which
-the checking can be handled. For example, consider the condition:
-.code
-dnslists = a.b.c=127.0.0.1
-.endd
-What happens if the DNS lookup for the incoming IP address yields both
-127.0.0.1 and 127.0.0.2 by means of two separate DNS records? Is the
-condition true because at least one given value was found, or is it false
-because at least one of the found values was not listed? And how does this
-affect negated conditions? Both possibilities are provided for with the help of
-additional separators &`==`& and &`=&&`&.
-
-.ilist
-If &`=`& or &`&&`& is used, the condition is true if any one of the looked up
-IP addresses matches one of the listed addresses. For the example above, the
-condition is true because 127.0.0.1 matches.
-.next
-If &`==`& or &`=&&`& is used, the condition is true only if every one of the
-looked up IP addresses matches one of the listed addresses. If the condition is
-changed to:
-.code
-dnslists = a.b.c==127.0.0.1
-.endd
-and the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
-false because 127.0.0.2 is not listed. You would need to have:
-.code
-dnslists = a.b.c==127.0.0.1,127.0.0.2
-.endd
-for the condition to be true.
-.endlist
-
-When &`!`& is used to negate IP address matching, it inverts the result, giving
-the precise opposite of the behaviour above. Thus:
-.ilist
-If &`!=`& or &`!&&`& is used, the condition is true if none of the looked up IP
-addresses matches one of the listed addresses. Consider:
-.code
-dnslists = a.b.c!&0.0.0.1
-.endd
-If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
-false because 127.0.0.1 matches.
-.next
-If &`!==`& or &`!=&&`& is used, the condition is true if there is at least one
-looked up IP address that does not match. Consider:
-.code
-dnslists = a.b.c!=&0.0.0.1
-.endd
-If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
-true, because 127.0.0.2 does not match. You would need to have:
-.code
-dnslists = a.b.c!=&0.0.0.1,0.0.0.2
-.endd
-for the condition to be false.
-.endlist
-When the DNS lookup yields only a single IP address, there is no difference
-between &`=`& and &`==`& and between &`&&`& and &`=&&`&.
-
-
-
-
-.section "Detailed information from merged DNS lists" "SECTmordetinf"
-.cindex "DNS list" "information from merged"
-When the facility for restricting the matching IP values in a DNS list is used,
-the text from the TXT record that is set in &$dnslist_text$& may not reflect
-the true reason for rejection. This happens when lists are merged and the IP
-address in the A record is used to distinguish them; unfortunately there is
-only one TXT record. One way round this is not to use merged lists, but that
-can be inefficient because it requires multiple DNS lookups where one would do
-in the vast majority of cases when the host of interest is not on any of the
-lists.
-
-A less inefficient way of solving this problem is available. If
-two domain names, comma-separated, are given, the second is used first to
-do an initial check, making use of any IP value restrictions that are set.
-If there is a match, the first domain is used, without any IP value
-restrictions, to get the TXT record. As a byproduct of this, there is also
-a check that the IP being tested is indeed on the first list. The first
-domain is the one that is put in &$dnslist_domain$&. For example:
-.code
-deny message  = \
-         rejected because $sender_host_address is blacklisted \
-         at $dnslist_domain\n$dnslist_text
-       dnslists = \
-         sbl.spamhaus.org,sbl-xbl.spamhaus.org=127.0.0.2 : \
-         dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
-.endd
-For the first blacklist item, this starts by doing a lookup in
-&'sbl-xbl.spamhaus.org'& and testing for a 127.0.0.2 return. If there is a
-match, it then looks in &'sbl.spamhaus.org'&, without checking the return
-value, and as long as something is found, it looks for the corresponding TXT
-record. If there is no match in &'sbl-xbl.spamhaus.org'&, nothing more is done.
-The second blacklist item is processed similarly.
-
-If you are interested in more than one merged list, the same list must be
-given several times, but because the results of the DNS lookups are cached,
-the DNS calls themselves are not repeated. For example:
-.code
-deny dnslists = \
-         http.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.2 : \
-         socks.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.3 : \
-         misc.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.4 : \
-         dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
-.endd
-In this case there is one lookup in &'dnsbl.sorbs.net'&, and if none of the IP
-values matches (or if no record is found), this is the only lookup that is
-done. Only if there is a match is one of the more specific lists consulted.
-
-
-
-.section "DNS lists and IPv6" "SECTmorednslistslast"
-.cindex "IPv6" "DNS black lists"
-.cindex "DNS list" "IPv6 usage"
-If Exim is asked to do a dnslist lookup for an IPv6 address, it inverts it
-nibble by nibble. For example, if the calling host's IP address is
-3ffe:ffff:836f:0a00:000a:0800:200a:c031, Exim might look up
-.code
-1.3.0.c.a.0.0.2.0.0.8.0.a.0.0.0.0.0.a.0.f.6.3.8.
-  f.f.f.f.e.f.f.3.blackholes.mail-abuse.org
-.endd
-(split over two lines here to fit on the page). Unfortunately, some of the DNS
-lists contain wildcard records, intended for IPv4, that interact badly with
-IPv6. For example, the DNS entry
-.code
-*.3.some.list.example.    A    127.0.0.1
-.endd
-is probably intended to put the entire 3.0.0.0/8 IPv4 network on the list.
-Unfortunately, it also matches the entire 3::/4 IPv6 network.
-
-You can exclude IPv6 addresses from DNS lookups by making use of a suitable
-&%condition%& condition, as in this example:
-.code
-deny   condition = ${if isip4{$sender_host_address}}
-       dnslists  = some.list.example
-.endd
-
-If an explicit key is being used for a DNS lookup and it may be an IPv6
-address you should specify alternate list separators for both the outer
-(DNS list name) list and inner (lookup keys) list:
-.code
-       dnslists = <; dnsbl.example.com/<|$acl_m_addrslist
-.endd
-
-.section "Rate limiting incoming messages" "SECTratelimiting"
-.cindex "rate limiting" "client sending"
-.cindex "limiting client sending rates"
-.oindex "&%smtp_ratelimit_*%&"
-The &%ratelimit%& ACL condition can be used to measure and control the rate at
-which clients can send email. This is more powerful than the
-&%smtp_ratelimit_*%& options, because those options control the rate of
-commands in a single SMTP session only, whereas the &%ratelimit%& condition
-works across all connections (concurrent and sequential) from the same client
-host. The syntax of the &%ratelimit%& condition is:
-.display
-&`ratelimit =`& <&'m'&> &`/`& <&'p'&> &`/`& <&'options'&> &`/`& <&'key'&>
-.endd
-If the average client sending rate is less than &'m'& messages per time
-period &'p'& then the condition is false; otherwise it is true.
-
-As a side-effect, the &%ratelimit%& condition sets the expansion variable
-&$sender_rate$& to the client's computed rate, &$sender_rate_limit$& to the
-configured value of &'m'&, and &$sender_rate_period$& to the configured value
-of &'p'&.
-
-The parameter &'p'& is the smoothing time constant, in the form of an Exim
-time interval, for example, &`8h`& for eight hours. A larger time constant
-means that it takes Exim longer to forget a client's past behaviour. The
-parameter &'m'& is the maximum number of messages that a client is permitted to
-send in each time interval. It also specifies the number of messages permitted
-in a fast burst. By increasing both &'m'& and &'p'& but keeping &'m/p'&
-constant, you can allow a client to send more messages in a burst without
-changing its long-term sending rate limit. Conversely, if &'m'& and &'p'& are
-both small, messages must be sent at an even rate.
-
-There is a script in &_util/ratelimit.pl_& which extracts sending rates from
-log files, to assist with choosing appropriate settings for &'m'& and &'p'&
-when deploying the &%ratelimit%& ACL condition. The script prints usage
-instructions when it is run with no arguments.
-
-The key is used to look up the data for calculating the client's average
-sending rate. This data is stored in Exim's spool directory, alongside the
-retry and other hints databases. The default key is &$sender_host_address$&,
-which means Exim computes the sending rate of each client host IP address.
-By changing the key you can change how Exim identifies clients for the purpose
-of ratelimiting. For example, to limit the sending rate of each authenticated
-user, independent of the computer they are sending from, set the key to
-&$authenticated_id$&. You must ensure that the lookup key is meaningful; for
-example, &$authenticated_id$& is only meaningful if the client has
-authenticated (which you can check with the &%authenticated%& ACL condition).
-
-The lookup key does not have to identify clients: If you want to limit the
-rate at which a recipient receives messages, you can use the key
-&`$local_part@$domain`& with the &%per_rcpt%& option (see below) in a RCPT
-ACL.
-
-Each &%ratelimit%& condition can have up to four options. A &%per_*%& option
-specifies what Exim measures the rate of, for example, messages or recipients
-or bytes. You can adjust the measurement using the &%unique=%& and/or
-&%count=%& options. You can also control when Exim updates the recorded rate
-using a &%strict%&, &%leaky%&, or &%readonly%& option. The options are
-separated by a slash, like the other parameters. They may appear in any order.
-
-Internally, Exim appends the smoothing constant &'p'& onto the lookup key with
-any options that alter the meaning of the stored data. The limit &'m'& is not
-stored, so you can alter the configured maximum rate and Exim will still
-remember clients' past behaviour. If you change the &%per_*%& mode or add or
-remove the &%unique=%& option, the lookup key changes so Exim will forget past
-behaviour. The lookup key is not affected by changes to the update mode and
-the &%count=%& option.
-
-
-.section "Ratelimit options for what is being measured" "ratoptmea"
-.cindex "rate limiting" "per_* options"
-The &%per_conn%& option limits the client's connection rate. It is not
-normally used in the &%acl_not_smtp%&, &%acl_not_smtp_mime%&, or
-&%acl_not_smtp_start%& ACLs.
-
-The &%per_mail%& option limits the client's rate of sending messages. This is
-the default if none of the &%per_*%& options is specified. It can be used in
-&%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&, &%acl_smtp_mime%&,
-&%acl_smtp_data%&, or &%acl_not_smtp%&.
-
-The &%per_byte%& option limits the sender's email bandwidth. It can be used in
-the same ACLs as the &%per_mail%& option, though it is best to use this option
-in the &%acl_smtp_mime%&, &%acl_smtp_data%& or &%acl_not_smtp%& ACLs; if it is
-used in an earlier ACL, Exim relies on the SIZE parameter given by the client
-in its MAIL command, which may be inaccurate or completely missing. You can
-follow the limit &'m'& in the configuration with K, M, or G to specify limits
-in kilobytes, megabytes, or gigabytes, respectively.
-
-The &%per_rcpt%& option causes Exim to limit the rate at which recipients are
-accepted. It can be used in the &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
-&%acl_smtp_mime%&, &%acl_smtp_data%&, or &%acl_smtp_rcpt%& ACLs. In
-&%acl_smtp_rcpt%& the rate is updated one recipient at a time; in the other
-ACLs the rate is updated with the total (accepted) recipient count in one go. Note that
-in either case the rate limiting engine will see a message with many
-recipients as a large high-speed burst.
-
-The &%per_addr%& option is like the &%per_rcpt%& option, except it counts the
-number of different recipients that the client has sent messages to in the
-last time period. That is, if the client repeatedly sends messages to the same
-recipient, its measured rate is not increased. This option can only be used in
-&%acl_smtp_rcpt%&.
-
-The &%per_cmd%& option causes Exim to recompute the rate every time the
-condition is processed. This can be used to limit the rate of any SMTP
-command. If it is used in multiple ACLs it can limit the aggregate rate of
-multiple different commands.
-
-The &%count=%& option can be used to alter how much Exim adds to the client's
-measured rate. For example, the &%per_byte%& option is equivalent to
-&`per_mail/count=$message_size`&. If there is no &%count=%& option, Exim
-increases the measured rate by one (except for the &%per_rcpt%& option in ACLs
-other than &%acl_smtp_rcpt%&). The count does not have to be an integer.
-
-The &%unique=%& option is described in section &<<ratoptuniq>>& below.
-
-
-.section "Ratelimit update modes" "ratoptupd"
-.cindex "rate limiting" "reading data without updating"
-You can specify one of three options with the &%ratelimit%& condition to
-control when its database is updated. This section describes the &%readonly%&
-mode, and the next section describes the &%strict%& and &%leaky%& modes.
-
-If the &%ratelimit%& condition is used in &%readonly%& mode, Exim looks up a
-previously-computed rate to check against the limit.
-
-For example, you can test the client's sending rate and deny it access (when
-it is too fast) in the connect ACL. If the client passes this check then it
-can go on to send a message, in which case its recorded rate will be updated
-in the MAIL ACL. Subsequent connections from the same client will check this
-new rate.
-.code
-acl_check_connect:
- deny ratelimit = 100 / 5m / readonly
-    log_message = RATE CHECK: $sender_rate/$sender_rate_period \
-                  (max $sender_rate_limit)
-# ...
-acl_check_mail:
- warn ratelimit = 100 / 5m / strict
-    log_message = RATE UPDATE: $sender_rate/$sender_rate_period \
-                  (max $sender_rate_limit)
-.endd
-
-If Exim encounters multiple &%ratelimit%& conditions with the same key when
-processing a message then it may increase the client's measured rate more than
-it should. For example, this will happen if you check the &%per_rcpt%& option
-in both &%acl_smtp_rcpt%& and &%acl_smtp_data%&. However it's OK to check the
-same &%ratelimit%& condition multiple times in the same ACL. You can avoid any
-multiple update problems by using the &%readonly%& option on later ratelimit
-checks.
-
-The &%per_*%& options described above do not make sense in some ACLs. If you
-use a &%per_*%& option in an ACL where it is not normally permitted then the
-update mode defaults to &%readonly%& and you cannot specify the &%strict%& or
-&%leaky%& modes. In other ACLs the default update mode is &%leaky%& (see the
-next section) so you must specify the &%readonly%& option explicitly.
-
-
-.section "Ratelimit options for handling fast clients" "ratoptfast"
-.cindex "rate limiting" "strict and leaky modes"
-If a client's average rate is greater than the maximum, the rate limiting
-engine can react in two possible ways, depending on the presence of the
-&%strict%& or &%leaky%& update modes. This is independent of the other
-counter-measures (such as rejecting the message) that may be specified by the
-rest of the ACL.
-
-The &%leaky%& (default) option means that the client's recorded rate is not
-updated if it is above the limit. The effect of this is that Exim measures the
-client's average rate of successfully sent email,
-up to the given limit.
-This is appropriate if the countermeasure when the condition is true
-consists of refusing the message, and
-is generally the better choice if you have clients that retry automatically.
-If the action when true is anything more complex then this option is
-likely not what is wanted.
-
-The &%strict%& option means that the client's recorded rate is always
-updated. The effect of this is that Exim measures the client's average rate
-of attempts to send email, which can be much higher than the maximum it is
-actually allowed. If the client is over the limit it may be subjected to
-counter-measures by the ACL. It must slow down and allow sufficient time to
-pass that its computed rate falls below the maximum before it can send email
-again. The time (the number of smoothing periods) it must wait and not
-attempt to send mail can be calculated with this formula:
-.code
-        ln(peakrate/maxrate)
-.endd
-
-
-.section "Limiting the rate of different events" "ratoptuniq"
-.cindex "rate limiting" "counting unique events"
-The &%ratelimit%& &%unique=%& option controls a mechanism for counting the
-rate of different events. For example, the &%per_addr%& option uses this
-mechanism to count the number of different recipients that the client has
-sent messages to in the last time period; it is equivalent to
-&`per_rcpt/unique=$local_part@$domain`&. You could use this feature to
-measure the rate that a client uses different sender addresses with the
-options &`per_mail/unique=$sender_address`&.
-
-For each &%ratelimit%& key Exim stores the set of &%unique=%& values that it
-has seen for that key. The whole set is thrown away when it is older than the
-rate smoothing period &'p'&, so each different event is counted at most once
-per period. In the &%leaky%& update mode, an event that causes the client to
-go over the limit is not added to the set, in the same way that the client's
-recorded rate is not updated in the same situation.
-
-When you combine the &%unique=%& and &%readonly%& options, the specific
-&%unique=%& value is ignored, and Exim just retrieves the client's stored
-rate.
-
-The &%unique=%& mechanism needs more space in the ratelimit database than the
-other &%ratelimit%& options in order to store the event set. The number of
-unique values is potentially as large as the rate limit, so the extra space
-required increases with larger limits.
-
-The uniqueification is not perfect: there is a small probability that Exim
-will think a new event has happened before. If the sender's rate is less than
-the limit, Exim should be more than 99.9% correct. However in &%strict%& mode
-the measured rate can go above the limit, in which case Exim may under-count
-events by a significant margin. Fortunately, if the rate is high enough (2.7
-times the limit) that the false positive rate goes above 9%, then Exim will
-throw away the over-full event set before the measured rate falls below the
-limit. Therefore the only harm should be that exceptionally high sending rates
-are logged incorrectly; any countermeasures you configure will be as effective
-as intended.
-
-
-.section "Using rate limiting" "useratlim"
-Exim's other ACL facilities are used to define what counter-measures are taken
-when the rate limit is exceeded. This might be anything from logging a warning
-(for example, while measuring existing sending rates in order to define
-policy), through time delays to slow down fast senders, up to rejecting the
-message. For example:
-.code
-# Log all senders' rates
-warn ratelimit = 0 / 1h / strict
-     log_message = Sender rate $sender_rate / $sender_rate_period
-
-# Slow down fast senders; note the need to truncate $sender_rate
-# at the decimal point.
-warn ratelimit = 100 / 1h / per_rcpt / strict
-     delay     = ${eval: ${sg{$sender_rate}{[.].*}{}} - \
-                   $sender_rate_limit }s
-
-# Keep authenticated users under control
-deny authenticated = *
-     ratelimit = 100 / 1d / strict / $authenticated_id
-
-# System-wide rate limit
-defer message = Sorry, too busy. Try again later.
-     ratelimit = 10 / 1s / $primary_hostname
-
-# Restrict incoming rate from each host, with a default
-# set using a macro and special cases looked up in a table.
-defer message = Sender rate exceeds $sender_rate_limit \
-               messages per $sender_rate_period
-     ratelimit = ${lookup {$sender_host_address} \
-                   cdb {DB/ratelimits.cdb} \
-                   {$value} {RATELIMIT} }
-.endd
-&*Warning*&: If you have a busy server with a lot of &%ratelimit%& tests,
-especially with the &%per_rcpt%& option, you may suffer from a performance
-bottleneck caused by locking on the ratelimit hints database. Apart from
-making your ACLs less complicated, you can reduce the problem by using a
-RAM disk for Exim's hints directory (usually &_/var/spool/exim/db/_&). However
-this means that Exim will lose its hints data after a reboot (including retry
-hints, the callout cache, and ratelimit data).
-
-
-
-.section "Address verification" "SECTaddressverification"
-.cindex "verifying address" "options for"
-.cindex "policy control" "address verification"
-Several of the &%verify%& conditions described in section
-&<<SECTaclconditions>>& cause addresses to be verified. Section
-&<<SECTsenaddver>>& discusses the reporting of sender verification failures.
-The verification conditions can be followed by options that modify the
-verification process. The options are separated from the keyword and from each
-other by slashes, and some of them contain parameters. For example:
-.code
-verify = sender/callout
-verify = recipient/defer_ok/callout=10s,defer_ok
-.endd
-The first stage of address verification, which always happens, is to run the
-address through the routers, in &"verify mode"&. Routers can detect the
-difference between verification and routing for delivery, and their actions can
-be varied by a number of generic options such as &%verify%& and &%verify_only%&
-(see chapter &<<CHAProutergeneric>>&). If routing fails, verification fails.
-The available options are as follows:
-
-.ilist
-If the &%callout%& option is specified, successful routing to one or more
-remote hosts is followed by a &"callout"& to those hosts as an additional
-check. Callouts and their sub-options are discussed in the next section.
-.next
-If there is a defer error while doing verification routing, the ACL
-normally returns &"defer"&. However, if you include &%defer_ok%& in the
-options, the condition is forced to be true instead. Note that this is a main
-verification option as well as a suboption for callouts.
-.next
-The &%no_details%& option is covered in section &<<SECTsenaddver>>&, which
-discusses the reporting of sender address verification failures.
-.next
-The &%success_on_redirect%& option causes verification always to succeed
-immediately after a successful redirection. By default, if a redirection
-generates just one address, that address is also verified. See further
-discussion in section &<<SECTredirwhilveri>>&.
-.endlist
-
-.cindex "verifying address" "differentiating failures"
-.vindex "&$recipient_verify_failure$&"
-.vindex "&$sender_verify_failure$&"
-.vindex "&$acl_verify_message$&"
-After an address verification failure, &$acl_verify_message$& contains the
-error message that is associated with the failure. It can be preserved by
-coding like this:
-.code
-warn  !verify = sender
-       set acl_m0 = $acl_verify_message
-.endd
-If you are writing your own custom rejection message or log message when
-denying access, you can use this variable to include information about the
-verification failure.
-
-In addition, &$sender_verify_failure$& or &$recipient_verify_failure$& (as
-appropriate) contains one of the following words:
-
-.ilist
-&%qualify%&: The address was unqualified (no domain), and the message
-was neither local nor came from an exempted host.
-.next
-&%route%&: Routing failed.
-.next
-&%mail%&: Routing succeeded, and a callout was attempted; rejection
-occurred at or before the MAIL command (that is, on initial
-connection, HELO, or MAIL).
-.next
-&%recipient%&: The RCPT command in a callout was rejected.
-.next
-&%postmaster%&: The postmaster check in a callout was rejected.
-.endlist
-
-The main use of these variables is expected to be to distinguish between
-rejections of MAIL and rejections of RCPT in callouts.
-
-The above variables may also be set after a &*successful*&
-address verification to:
-
-.ilist
-&%random%&: A random local-part callout succeeded
-.endlist
-
-
-
-
-.section "Callout verification" "SECTcallver"
-.cindex "verifying address" "by callout"
-.cindex "callout" "verification"
-.cindex "SMTP" "callout verification"
-For non-local addresses, routing verifies the domain, but is unable to do any
-checking of the local part. There are situations where some means of verifying
-the local part is desirable. One way this can be done is to make an SMTP
-&'callback'& to a delivery host for the sender address or a &'callforward'& to
-a subsequent host for a recipient address, to see if the host accepts the
-address. We use the term &'callout'& to cover both cases. Note that for a
-sender address, the callback is not to the client host that is trying to
-deliver the message, but to one of the hosts that accepts incoming mail for the
-sender's domain.
-
-Exim does not do callouts by default. If you want them to happen, you must
-request them by setting appropriate options on the &%verify%& condition, as
-described below. This facility should be used with care, because it can add a
-lot of resource usage to the cost of verifying an address. However, Exim does
-cache the results of callouts, which helps to reduce the cost. Details of
-caching are in section &<<SECTcallvercache>>&.
-
-Recipient callouts are usually used only between hosts that are controlled by
-the same administration. For example, a corporate gateway host could use
-callouts to check for valid recipients on an internal mailserver. A successful
-callout does not guarantee that a real delivery to the address would succeed;
-on the other hand, a failing callout does guarantee that a delivery would fail.
-
-If the &%callout%& option is present on a condition that verifies an address, a
-second stage of verification occurs if the address is successfully routed to
-one or more remote hosts. The usual case is routing by a &(dnslookup)& or a
-&(manualroute)& router, where the router specifies the hosts. However, if a
-router that does not set up hosts routes to an &(smtp)& transport with a
-&%hosts%& setting, the transport's hosts are used. If an &(smtp)& transport has
-&%hosts_override%& set, its hosts are always used, whether or not the router
-supplies a host list.
-Callouts are only supported on &(smtp)& transports.
-
-The port that is used is taken from the transport, if it is specified and is a
-remote transport. (For routers that do verification only, no transport need be
-specified.) Otherwise, the default SMTP port is used. If a remote transport
-specifies an outgoing interface, this is used; otherwise the interface is not
-specified. Likewise, the text that is used for the HELO command is taken from
-the transport's &%helo_data%& option; if there is no transport, the value of
-&$smtp_active_hostname$& is used.
-
-For a sender callout check, Exim makes SMTP connections to the remote hosts, to
-test whether a bounce message could be delivered to the sender address. The
-following SMTP commands are sent:
-.display
-&`HELO `&<&'local host name'&>
-&`MAIL FROM:<>`&
-&`RCPT TO:`&<&'the address to be tested'&>
-&`QUIT`&
-.endd
-LHLO is used instead of HELO if the transport's &%protocol%& option is
-set to &"lmtp"&.
-
-The callout may use EHLO, AUTH and/or STARTTLS given appropriate option
-settings.
-
-A recipient callout check is similar. By default, it also uses an empty address
-for the sender. This default is chosen because most hosts do not make use of
-the sender address when verifying a recipient. Using the same address means
-that a single cache entry can be used for each recipient. Some sites, however,
-do make use of the sender address when verifying. These are catered for by the
-&%use_sender%& and &%use_postmaster%& options, described in the next section.
-
-If the response to the RCPT command is a 2&'xx'& code, the verification
-succeeds. If it is 5&'xx'&, the verification fails. For any other condition,
-Exim tries the next host, if any. If there is a problem with all the remote
-hosts, the ACL yields &"defer"&, unless the &%defer_ok%& parameter of the
-&%callout%& option is given, in which case the condition is forced to succeed.
-
-.cindex "SMTP" "output flushing, disabling for callout"
-A callout may take a little time. For this reason, Exim normally flushes SMTP
-output before performing a callout in an ACL, to avoid unexpected timeouts in
-clients when the SMTP PIPELINING extension is in use. The flushing can be
-disabled by using a &%control%& modifier to set &%no_callout_flush%&.
-
-
-
-
-.section "Additional parameters for callouts" "CALLaddparcall"
-.cindex "callout" "additional parameters for"
-The &%callout%& option can be followed by an equals sign and a number of
-optional parameters, separated by commas. For example:
-.code
-verify = recipient/callout=10s,defer_ok
-.endd
-The old syntax, which had &%callout_defer_ok%& and &%check_postmaster%& as
-separate verify options, is retained for backwards compatibility, but is now
-deprecated. The additional parameters for &%callout%& are as follows:
-
-
-.vlist
-.vitem <&'a&~time&~interval'&>
-.cindex "callout" "timeout, specifying"
-This specifies the timeout that applies for the callout attempt to each host.
-For example:
-.code
-verify = sender/callout=5s
-.endd
-The default is 30 seconds. The timeout is used for each response from the
-remote host. It is also used for the initial connection, unless overridden by
-the &%connect%& parameter.
-
-
-.vitem &*connect&~=&~*&<&'time&~interval'&>
-.cindex "callout" "connection timeout, specifying"
-This parameter makes it possible to set a different (usually smaller) timeout
-for making the SMTP connection. For example:
-.code
-verify = sender/callout=5s,connect=1s
-.endd
-If not specified, this timeout defaults to the general timeout value.
-
-.vitem &*defer_ok*&
-.cindex "callout" "defer, action on"
-When this parameter is present, failure to contact any host, or any other kind
-of temporary error, is treated as success by the ACL. However, the cache is not
-updated in this circumstance.
-
-.vitem &*fullpostmaster*&
-.cindex "callout" "full postmaster check"
-This operates like the &%postmaster%& option (see below), but if the check for
-&'postmaster@domain'& fails, it tries just &'postmaster'&, without a domain, in
-accordance with the specification in RFC 2821. The RFC states that the
-unqualified address &'postmaster'& should be accepted.
-
-
-.vitem &*mailfrom&~=&~*&<&'email&~address'&>
-.cindex "callout" "sender when verifying header"
-When verifying addresses in header lines using the &%header_sender%&
-verification option, Exim behaves by default as if the addresses are envelope
-sender addresses from a message. Callout verification therefore tests to see
-whether a bounce message could be delivered, by using an empty address in the
-MAIL command. However, it is arguable that these addresses might never be used
-as envelope senders, and could therefore justifiably reject bounce messages
-(empty senders). The &%mailfrom%& callout parameter allows you to specify what
-address to use in the MAIL command. For example:
-.code
-require  verify = header_sender/callout=mailfrom=abcd@x.y.z
-.endd
-This parameter is available only for the &%header_sender%& verification option.
-
-
-.vitem &*maxwait&~=&~*&<&'time&~interval'&>
-.cindex "callout" "overall timeout, specifying"
-This parameter sets an overall timeout for performing a callout verification.
-For example:
-.code
-verify = sender/callout=5s,maxwait=30s
-.endd
-This timeout defaults to four times the callout timeout for individual SMTP
-commands. The overall timeout applies when there is more than one host that can
-be tried. The timeout is checked before trying the next host. This prevents
-very long delays if there are a large number of hosts and all are timing out
-(for example, when network connections are timing out).
-
-
-.vitem &*no_cache*&
-.cindex "callout" "cache, suppressing"
-.cindex "caching callout, suppressing"
-When this parameter is given, the callout cache is neither read nor updated.
-
-.vitem &*postmaster*&
-.cindex "callout" "postmaster; checking"
-When this parameter is set, a successful callout check is followed by a similar
-check for the local part &'postmaster'& at the same domain. If this address is
-rejected, the callout fails (but see &%fullpostmaster%& above). The result of
-the postmaster check is recorded in a cache record; if it is a failure, this is
-used to fail subsequent callouts for the domain without a connection being
-made, until the cache record expires.
-
-.vitem &*postmaster_mailfrom&~=&~*&<&'email&~address'&>
-The postmaster check uses an empty sender in the MAIL command by default.
-You can use this parameter to do a postmaster check using a different address.
-For example:
-.code
-require  verify = sender/callout=postmaster_mailfrom=abc@x.y.z
-.endd
-If both &%postmaster%& and &%postmaster_mailfrom%& are present, the rightmost
-one overrides. The &%postmaster%& parameter is equivalent to this example:
-.code
-require  verify = sender/callout=postmaster_mailfrom=
-.endd
-&*Warning*&: The caching arrangements for postmaster checking do not take
-account of the sender address. It is assumed that either the empty address or
-a fixed non-empty address will be used. All that Exim remembers is that the
-postmaster check for the domain succeeded or failed.
-
-
-.vitem &*random*&
-.cindex "callout" "&""random""& check"
-When this parameter is set, before doing the normal callout check, Exim does a
-check for a &"random"& local part at the same domain. The local part is not
-really random &-- it is defined by the expansion of the option
-&%callout_random_local_part%&, which defaults to
-.code
-$primary_hostname-$tod_epoch-testing
-.endd
-The idea here is to try to determine whether the remote host accepts all local
-parts without checking. If it does, there is no point in doing callouts for
-specific local parts. If the &"random"& check succeeds, the result is saved in
-a cache record, and used to force the current and subsequent callout checks to
-succeed without a connection being made, until the cache record expires.
-
-.vitem &*use_postmaster*&
-.cindex "callout" "sender for recipient check"
-This parameter applies to recipient callouts only. For example:
-.code
-deny  !verify = recipient/callout=use_postmaster
-.endd
-.vindex "&$qualify_domain$&"
-It causes a non-empty postmaster address to be used in the MAIL command when
-performing the callout for the recipient, and also for a &"random"& check if
-that is configured. The local part of the address is &`postmaster`& and the
-domain is the contents of &$qualify_domain$&.
-
-.vitem &*use_sender*&
-This option applies to recipient callouts only. For example:
-.code
-require  verify = recipient/callout=use_sender
-.endd
-It causes the message's actual sender address to be used in the MAIL
-command when performing the callout, instead of an empty address. There is no
-need to use this option unless you know that the called hosts make use of the
-sender when checking recipients. If used indiscriminately, it reduces the
-usefulness of callout caching.
-
-.vitem &*hold*&
-This option applies to recipient callouts only. For example:
-.code
-require  verify = recipient/callout=use_sender,hold
-.endd
-It causes the connection to be held open and used for any further recipients
-and for eventual delivery (should that be done quickly).
-Doing this saves on TCP and SMTP startup costs, and TLS costs also
-when that is used for the connections.
-The advantage is only gained if there are no callout cache hits
-(which could be enforced by the no_cache option),
-if the use_sender option is used,
-if neither the random nor the use_postmaster option is used,
-and if no other callouts intervene.
-.endlist
-
-If you use any of the parameters that set a non-empty sender for the MAIL
-command (&%mailfrom%&, &%postmaster_mailfrom%&, &%use_postmaster%&, or
-&%use_sender%&), you should think about possible loops. Recipient checking is
-usually done between two hosts that are under the same management, and the host
-that receives the callouts is not normally configured to do callouts itself.
-Therefore, it is normally safe to use &%use_postmaster%& or &%use_sender%& in
-these circumstances.
-
-However, if you use a non-empty sender address for a callout to an arbitrary
-host, there is the likelihood that the remote host will itself initiate a
-callout check back to your host. As it is checking what appears to be a message
-sender, it is likely to use an empty address in MAIL, thus avoiding a
-callout loop. However, to be on the safe side it would be best to set up your
-own ACLs so that they do not do sender verification checks when the recipient
-is the address you use for header sender or postmaster callout checking.
-
-Another issue to think about when using non-empty senders for callouts is
-caching. When you set &%mailfrom%& or &%use_sender%&, the cache record is keyed
-by the sender/recipient combination; thus, for any given recipient, many more
-actual callouts are performed than when an empty sender or postmaster is used.
-
-
-
-
-.section "Callout caching" "SECTcallvercache"
-.cindex "hints database" "callout cache"
-.cindex "callout" "cache, description of"
-.cindex "caching" "callout"
-Exim caches the results of callouts in order to reduce the amount of resources
-used, unless you specify the &%no_cache%& parameter with the &%callout%&
-option. A hints database called &"callout"& is used for the cache. Two
-different record types are used: one records the result of a callout check for
-a specific address, and the other records information that applies to the
-entire domain (for example, that it accepts the local part &'postmaster'&).
-
-When an original callout fails, a detailed SMTP error message is given about
-the failure. However, for subsequent failures use the cache data, this message
-is not available.
-
-The expiry times for negative and positive address cache records are
-independent, and can be set by the global options &%callout_negative_expire%&
-(default 2h) and &%callout_positive_expire%& (default 24h), respectively.
-
-If a host gives a negative response to an SMTP connection, or rejects any
-commands up to and including
-.code
-MAIL FROM:<>
-.endd
-(but not including the MAIL command with a non-empty address),
-any callout attempt is bound to fail. Exim remembers such failures in a
-domain cache record, which it uses to fail callouts for the domain without
-making new connections, until the domain record times out. There are two
-separate expiry times for domain cache records:
-&%callout_domain_negative_expire%& (default 3h) and
-&%callout_domain_positive_expire%& (default 7d).
-
-Domain records expire when the negative expiry time is reached if callouts
-cannot be made for the domain, or if the postmaster check failed.
-Otherwise, they expire when the positive expiry time is reached. This
-ensures that, for example, a host that stops accepting &"random"& local parts
-will eventually be noticed.
-
-The callout caching mechanism is based on the domain of the address that is
-being tested. If the domain routes to several hosts, it is assumed that their
-behaviour will be the same.
-
-
-
-.section "Sender address verification reporting" "SECTsenaddver"
-.cindex "verifying" "suppressing error details"
-See section &<<SECTaddressverification>>& for a general discussion of
-verification. When sender verification fails in an ACL, the details of the
-failure are given as additional output lines before the 550 response to the
-relevant SMTP command (RCPT or DATA). For example, if sender callout is in use,
-you might see:
-.code
-MAIL FROM:<xyz@abc.example>
-250 OK
-RCPT TO:<pqr@def.example>
-550-Verification failed for <xyz@abc.example>
-550-Called:   192.168.34.43
-550-Sent:     RCPT TO:<xyz@abc.example>
-550-Response: 550 Unknown local part xyz in <xyz@abc.example>
-550 Sender verification failed
-.endd
-If more than one RCPT command fails in the same way, the details are given
-only for the first of them. However, some administrators do not want to send
-out this much information. You can suppress the details by adding
-&`/no_details`& to the ACL statement that requests sender verification. For
-example:
-.code
-verify = sender/no_details
-.endd
-
-.section "Redirection while verifying" "SECTredirwhilveri"
-.cindex "verifying" "redirection while"
-.cindex "address redirection" "while verifying"
-A dilemma arises when a local address is redirected by aliasing or forwarding
-during verification: should the generated addresses themselves be verified,
-or should the successful expansion of the original address be enough to verify
-it? By default, Exim takes the following pragmatic approach:
-
-.ilist
-When an incoming address is redirected to just one child address, verification
-continues with the child address, and if that fails to verify, the original
-verification also fails.
-.next
-When an incoming address is redirected to more than one child address,
-verification does not continue. A success result is returned.
-.endlist
-
-This seems the most reasonable behaviour for the common use of aliasing as a
-way of redirecting different local parts to the same mailbox. It means, for
-example, that a pair of alias entries of the form
-.code
-A.Wol:   aw123
-aw123:   :fail: Gone away, no forwarding address
-.endd
-work as expected, with both local parts causing verification failure. When a
-redirection generates more than one address, the behaviour is more like a
-mailing list, where the existence of the alias itself is sufficient for
-verification to succeed.
-
-It is possible, however, to change the default behaviour so that all successful
-redirections count as successful verifications, however many new addresses are
-generated. This is specified by the &%success_on_redirect%& verification
-option. For example:
-.code
-require verify = recipient/success_on_redirect/callout=10s
-.endd
-In this example, verification succeeds if a router generates a new address, and
-the callout does not occur, because no address was routed to a remote host.
-
-When verification is being tested via the &%-bv%& option, the treatment of
-redirections is as just described, unless the &%-v%& or any debugging option is
-also specified. In that case, full verification is done for every generated
-address and a report is output for each of them.
-
-
-
-.section "Client SMTP authorization (CSA)" "SECTverifyCSA"
-.cindex "CSA" "verifying"
-Client SMTP Authorization is a system that allows a site to advertise
-which machines are and are not permitted to send email. This is done by placing
-special SRV records in the DNS; these are looked up using the client's HELO
-domain. At the time of writing, CSA is still an Internet Draft. Client SMTP
-Authorization checks in Exim are performed by the ACL condition:
-.code
-verify = csa
-.endd
-This fails if the client is not authorized. If there is a DNS problem, or if no
-valid CSA SRV record is found, or if the client is authorized, the condition
-succeeds. These three cases can be distinguished using the expansion variable
-&$csa_status$&, which can take one of the values &"fail"&, &"defer"&,
-&"unknown"&, or &"ok"&. The condition does not itself defer because that would
-be likely to cause problems for legitimate email.
-
-The error messages produced by the CSA code include slightly more
-detail. If &$csa_status$& is &"defer"&, this may be because of problems
-looking up the CSA SRV record, or problems looking up the CSA target
-address record. There are four reasons for &$csa_status$& being &"fail"&:
-
-.ilist
-The client's host name is explicitly not authorized.
-.next
-The client's IP address does not match any of the CSA target IP addresses.
-.next
-The client's host name is authorized but it has no valid target IP addresses
-(for example, the target's addresses are IPv6 and the client is using IPv4).
-.next
-The client's host name has no CSA SRV record but a parent domain has asserted
-that all subdomains must be explicitly authorized.
-.endlist
-
-The &%csa%& verification condition can take an argument which is the domain to
-use for the DNS query. The default is:
-.code
-verify = csa/$sender_helo_name
-.endd
-This implementation includes an extension to CSA. If the query domain
-is an address literal such as [192.0.2.95], or if it is a bare IP
-address, Exim searches for CSA SRV records in the reverse DNS as if
-the HELO domain was (for example) &'95.2.0.192.in-addr.arpa'&. Therefore it is
-meaningful to say:
-.code
-verify = csa/$sender_host_address
-.endd
-In fact, this is the check that Exim performs if the client does not say HELO.
-This extension can be turned off by setting the main configuration option
-&%dns_csa_use_reverse%& to be false.
-
-If a CSA SRV record is not found for the domain itself, a search
-is performed through its parent domains for a record which might be
-making assertions about subdomains. The maximum depth of this search is limited
-using the main configuration option &%dns_csa_search_limit%&, which is 5 by
-default. Exim does not look for CSA SRV records in a top level domain, so the
-default settings handle HELO domains as long as seven
-(&'hostname.five.four.three.two.one.com'&). This encompasses the vast majority
-of legitimate HELO domains.
-
-The &'dnsdb'& lookup also has support for CSA. Although &'dnsdb'& also supports
-direct SRV lookups, this is not sufficient because of the extra parent domain
-search behaviour of CSA, and (as with PTR lookups) &'dnsdb'& also turns IP
-addresses into lookups in the reverse DNS space. The result of a successful
-lookup such as:
-.code
-${lookup dnsdb {csa=$sender_helo_name}}
-.endd
-has two space-separated fields: an authorization code and a target host name.
-The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
-authorization required but absent, or &"?"& for unknown.
-
-
-
-
-.section "Bounce address tag validation" "SECTverifyPRVS"
-.cindex "BATV, verifying"
-Bounce address tag validation (BATV) is a scheme whereby the envelope senders
-of outgoing messages have a cryptographic, timestamped &"tag"& added to them.
-Genuine incoming bounce messages should therefore always be addressed to
-recipients that have a valid tag. This scheme is a way of detecting unwanted
-bounce messages caused by sender address forgeries (often called &"collateral
-spam"&), because the recipients of such messages do not include valid tags.
-
-There are two expansion items to help with the implementation of the BATV
-&"prvs"& (private signature) scheme in an Exim configuration. This scheme signs
-the original envelope sender address by using a simple key to add a hash of the
-address and some time-based randomizing information. The &%prvs%& expansion
-item creates a signed address, and the &%prvscheck%& expansion item checks one.
-The syntax of these expansion items is described in section
-&<<SECTexpansionitems>>&.
-The validity period on signed addresses is seven days.
-
-As an example, suppose the secret per-address keys are stored in an MySQL
-database. A query to look up the key for an address could be defined as a macro
-like this:
-.code
-PRVSCHECK_SQL = ${lookup mysql{SELECT secret FROM batv_prvs \
-                WHERE sender='${quote_mysql:$prvscheck_address}'\
-                }{$value}}
-.endd
-Suppose also that the senders who make use of BATV are defined by an address
-list called &%batv_senders%&. Then, in the ACL for RCPT commands, you could
-use this:
-.code
-# Bounces: drop unsigned addresses for BATV senders
-deny message = This address does not send an unsigned reverse path
-     senders = :
-     recipients = +batv_senders
-
-# Bounces: In case of prvs-signed address, check signature.
-deny message = Invalid reverse path signature.
-     senders = :
-     condition  = ${prvscheck {$local_part@$domain}\
-                  {PRVSCHECK_SQL}{1}}
-     !condition = $prvscheck_result
-.endd
-The first statement rejects recipients for bounce messages that are addressed
-to plain BATV sender addresses, because it is known that BATV senders do not
-send out messages with plain sender addresses. The second statement rejects
-recipients that are prvs-signed, but with invalid signatures (either because
-the key is wrong, or the signature has timed out).
-
-A non-prvs-signed address is not rejected by the second statement, because the
-&%prvscheck%& expansion yields an empty string if its first argument is not a
-prvs-signed address, thus causing the &%condition%& condition to be false. If
-the first argument is a syntactically valid prvs-signed address, the yield is
-the third string (in this case &"1"&), whether or not the cryptographic and
-timeout checks succeed. The &$prvscheck_result$& variable contains the result
-of the checks (empty for failure, &"1"& for success).
-
-There is one more issue you must consider when implementing prvs-signing:
-you have to ensure that the routers accept prvs-signed addresses and
-deliver them correctly. The easiest way to handle this is to use a &(redirect)&
-router to remove the signature with a configuration along these lines:
-.code
-batv_redirect:
-  driver = redirect
-  data = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}}
-.endd
-This works because, if the third argument of &%prvscheck%& is empty, the result
-of the expansion of a prvs-signed address is the decoded value of the original
-address. This router should probably be the first of your routers that handles
-local addresses.
-
-To create BATV-signed addresses in the first place, a transport of this form
-can be used:
-.code
-external_smtp_batv:
-  driver = smtp
-  return_path = ${prvs {$return_path} \
-                       {${lookup mysql{SELECT \
-                       secret FROM batv_prvs WHERE \
-                       sender='${quote_mysql:$sender_address}'} \
-                       {$value}fail}}}
-.endd
-If no key can be found for the existing return path, no signing takes place.
-
-
-
-.section "Using an ACL to control relaying" "SECTrelaycontrol"
-.cindex "&ACL;" "relay control"
-.cindex "relaying" "control by ACL"
-.cindex "policy control" "relay control"
-An MTA is said to &'relay'& a message if it receives it from some host and
-delivers it directly to another host as a result of a remote address contained
-within it. Redirecting a local address via an alias or forward file and then
-passing the message on to another host is not relaying,
-.cindex "&""percent hack""&"
-but a redirection as a result of the &"percent hack"& is.
-
-Two kinds of relaying exist, which are termed &"incoming"& and &"outgoing"&.
-A host which is acting as a gateway or an MX backup is concerned with incoming
-relaying from arbitrary hosts to a specific set of domains. On the other hand,
-a host which is acting as a smart host for a number of clients is concerned
-with outgoing relaying from those clients to the Internet at large. Often the
-same host is fulfilling both functions,
-. ///
-. as illustrated in the diagram below,
-. ///
-but in principle these two kinds of relaying are entirely independent. What is
-not wanted is the transmission of mail from arbitrary remote hosts through your
-system to arbitrary domains.
-
-
-You can implement relay control by means of suitable statements in the ACL that
-runs for each RCPT command. For convenience, it is often easiest to use
-Exim's named list facility to define the domains and hosts involved. For
-example, suppose you want to do the following:
-
-.ilist
-Deliver a number of domains to mailboxes on the local host (or process them
-locally in some other way). Let's say these are &'my.dom1.example'& and
-&'my.dom2.example'&.
-.next
-Relay mail for a number of other domains for which you are the secondary MX.
-These might be &'friend1.example'& and &'friend2.example'&.
-.next
-Relay mail from the hosts on your local LAN, to whatever domains are involved.
-Suppose your LAN is 192.168.45.0/24.
-.endlist
-
-
-In the main part of the configuration, you put the following definitions:
-.code
-domainlist local_domains    = my.dom1.example : my.dom2.example
-domainlist relay_to_domains = friend1.example : friend2.example
-hostlist   relay_from_hosts = 192.168.45.0/24
-.endd
-Now you can use these definitions in the ACL that is run for every RCPT
-command:
-.code
-acl_check_rcpt:
-  accept domains = +local_domains : +relay_to_domains
-  accept hosts   = +relay_from_hosts
-.endd
-The first statement accepts any RCPT command that contains an address in
-the local or relay domains. For any other domain, control passes to the second
-statement, which accepts the command only if it comes from one of the relay
-hosts. In practice, you will probably want to make your ACL more sophisticated
-than this, for example, by including sender and recipient verification. The
-default configuration includes a more comprehensive example, which is described
-in chapter &<<CHAPdefconfil>>&.
-
-
-
-.section "Checking a relay configuration" "SECTcheralcon"
-.cindex "relaying" "checking control of"
-You can check the relay characteristics of your configuration in the same way
-that you can test any ACL behaviour for an incoming SMTP connection, by using
-the &%-bh%& option to run a fake SMTP session with which you interact.
-.ecindex IIDacl
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "Content scanning at ACL time" "CHAPexiscan"
-.scindex IIDcosca "content scanning" "at ACL time"
-The extension of Exim to include content scanning at ACL time, formerly known
-as &"exiscan"&, was originally implemented as a patch by Tom Kistner. The code
-was integrated into the main source for Exim release 4.50, and Tom continues to
-maintain it. Most of the wording of this chapter is taken from Tom's
-specification.
-
-It is also possible to scan the content of messages at other times. The
-&[local_scan()]& function (see chapter &<<CHAPlocalscan>>&) allows for content
-scanning after all the ACLs have run. A transport filter can be used to scan
-messages at delivery time (see the &%transport_filter%& option, described in
-chapter &<<CHAPtransportgeneric>>&).
-
-If you want to include the ACL-time content-scanning features when you compile
-Exim, you need to arrange for WITH_CONTENT_SCAN to be defined in your
-&_Local/Makefile_&. When you do that, the Exim binary is built with:
-
-.ilist
-Two additional ACLs (&%acl_smtp_mime%& and &%acl_not_smtp_mime%&) that are run
-for all MIME parts for SMTP and non-SMTP messages, respectively.
-.next
-Additional ACL conditions and modifiers: &%decode%&, &%malware%&,
-&%mime_regex%&, &%regex%&, and &%spam%&. These can be used in the ACL that is
-run at the end of message reception (the &%acl_smtp_data%& ACL).
-.next
-An additional control feature (&"no_mbox_unspool"&) that saves spooled copies
-of messages, or parts of messages, for debugging purposes.
-.next
-Additional expansion variables that are set in the new ACL and by the new
-conditions.
-.next
-Two new main configuration options: &%av_scanner%& and &%spamd_address%&.
-.endlist
-
-Content-scanning is continually evolving, and new features are still being
-added. While such features are still unstable and liable to incompatible
-changes, they are made available in Exim by setting options whose names begin
-EXPERIMENTAL_ in &_Local/Makefile_&. Such features are not documented in
-this manual. You can find out about them by reading the file called
-&_doc/experimental.txt_&.
-
-All the content-scanning facilities work on a MBOX copy of the message that is
-temporarily created in a file called:
-.display
-<&'spool_directory'&>&`/scan/`&<&'message_id'&>/<&'message_id'&>&`.eml`&
-.endd
-The &_.eml_& extension is a friendly hint to virus scanners that they can
-expect an MBOX-like structure inside that file. The file is created when the
-first content scanning facility is called. Subsequent calls to content
-scanning conditions open the same file again. The directory is recursively
-removed when the &%acl_smtp_data%& ACL has finished running, unless
-.code
-control = no_mbox_unspool
-.endd
-has been encountered. When the MIME ACL decodes files, they are put into the
-same directory by default.
-
-
-
-.section "Scanning for viruses" "SECTscanvirus"
-.cindex "virus scanning"
-.cindex "content scanning" "for viruses"
-.cindex "content scanning" "the &%malware%& condition"
-The &%malware%& ACL condition lets you connect virus scanner software to Exim.
-It supports a &"generic"& interface to scanners called via the shell, and
-specialized interfaces for &"daemon"& type virus scanners, which are resident
-in memory and thus are much faster.
-
-Since message data needs to have arrived,
-the condition may be only called in ACL defined by
-&%acl_smtp_data%&,
-&%acl_smtp_data_prdr%&,
-&%acl_smtp_mime%& or
-&%acl_smtp_dkim%&
-
-A timeout of 2 minutes is applied to a scanner call (by default);
-if it expires then a defer action is taken.
-
-.oindex "&%av_scanner%&"
-You can set the &%av_scanner%& option in the main part of the configuration
-to specify which scanner to use, together with any additional options that
-are needed. The basic syntax is as follows:
-.display
-&`av_scanner = <`&&'scanner-type'&&`>:<`&&'option1'&&`>:<`&&'option2'&&`>:[...]`&
-.endd
-If you do not set &%av_scanner%&, it defaults to
-.code
-av_scanner = sophie:/var/run/sophie
-.endd
-If the value of &%av_scanner%& starts with a dollar character, it is expanded
-before use.
-The usual list-parsing of the content (see &<<SECTlistconstruct>>&) applies.
-The following scanner types are supported in this release,
-though individual ones can be included or not at build time:
-
-.vlist
-.vitem &%avast%&
-.cindex "virus scanners" "avast"
-This is the scanner daemon of Avast. It has been tested with Avast Core
-Security (currently at version 2.2.0).
-You can get a trial version at &url(https://www.avast.com) or for Linux
-at &url(https://www.avast.com/linux-server-antivirus).
-This scanner type takes one option,
-which can be either a full path to a UNIX socket,
-or host and port specifiers separated by white space.
-The host may be a name or an IP address; the port is either a
-single number or a pair of numbers with a dash between.
-A list of options may follow. These options are interpreted on the
-Exim's side of the malware scanner, or are given on separate lines to
-the daemon as options before the main scan command.
-
-.cindex &`pass_unscanned`& "avast"
-If &`pass_unscanned`&
-is set, any files the Avast scanner can't scan (e.g.
-decompression bombs, or invalid archives) are considered clean. Use with
-care.
-
-For example:
-.code
-av_scanner = avast:/var/run/avast/scan.sock:FLAGS -fullfiles:SENSITIVITY -pup
-av_scanner = avast:/var/run/avast/scan.sock:pass_unscanned:FLAGS -fullfiles:SENSITIVITY -pup
-av_scanner = avast:192.168.2.22 5036
-.endd
-If you omit the argument, the default path
-&_/var/run/avast/scan.sock_&
-is used.
-If you use a remote host,
-you need to make Exim's spool directory available to it,
-as the scanner is passed a file path, not file contents.
-For information about available commands and their options you may use
-.code
-$ socat UNIX:/var/run/avast/scan.sock STDIO:
-    FLAGS
-    SENSITIVITY
-    PACK
-.endd
-
-If the scanner returns a temporary failure (e.g. license issues, or
-permission problems), the message is deferred and a paniclog entry is
-written.  The usual &`defer_ok`& option is available.
-
-.vitem &%aveserver%&
-.cindex "virus scanners" "Kaspersky"
-This is the scanner daemon of Kaspersky Version 5. You can get a trial version
-at &url(https://www.kaspersky.com/). This scanner type takes one option,
-which is the path to the daemon's UNIX socket. The default is shown in this
-example:
-.code
-av_scanner = aveserver:/var/run/aveserver
-.endd
-
-
-.vitem &%clamd%&
-.cindex "virus scanners" "clamd"
-This daemon-type scanner is GPL and free. You can get it at
-&url(https://www.clamav.net/). Some older versions of clamd do not seem to
-unpack MIME containers, so it used to be recommended to unpack MIME attachments
-in the MIME ACL. This is no longer believed to be necessary.
-
-The options are a list of server specifiers, which may be
-a UNIX socket specification,
-a TCP socket specification,
-or a (global) option.
-
-A socket specification consists of a space-separated list.
-For a Unix socket the first element is a full path for the socket,
-for a TCP socket the first element is the IP address
-and the second a port number,
-Any further elements are per-server (non-global) options.
-These per-server options are supported:
-.code
-retry=<timespec>	Retry on connect fail
-.endd
-
-The &`retry`& option specifies a time after which a single retry for
-a failed connect is made.  The default is to not retry.
-
-If a Unix socket file is specified, only one server is supported.
-
-Examples:
-.code
-av_scanner = clamd:/opt/clamd/socket
-av_scanner = clamd:192.0.2.3 1234
-av_scanner = clamd:192.0.2.3 1234:local
-av_scanner = clamd:192.0.2.3 1234 retry=10s
-av_scanner = clamd:192.0.2.3 1234 : 192.0.2.4 1234
-.endd
-If the value of av_scanner points to a UNIX socket file or contains the
-&`local`&
-option, then the ClamAV interface will pass a filename containing the data
-to be scanned, which should normally result in less I/O happening and be
-more efficient.  Normally in the TCP case, the data is streamed to ClamAV as
-Exim does not assume that there is a common filesystem with the remote host.
-
-The final example shows that multiple TCP targets can be specified.  Exim will
-randomly use one for each incoming email (i.e. it load balances them).  Note
-that only TCP targets may be used if specifying a list of scanners; a UNIX
-socket cannot be mixed in with TCP targets.  If one of the servers becomes
-unavailable, Exim will try the remaining one(s) until it finds one that works.
-When a clamd server becomes unreachable, Exim will log a message.  Exim does
-not keep track of scanner state between multiple messages, and the scanner
-selection is random, so the message will get logged in the mainlog for each
-email that the down scanner gets chosen first (message wrapped to be readable):
-.code
-2013-10-09 14:30:39 1VTumd-0000Y8-BQ malware acl condition:
-   clamd: connection to localhost, port 3310 failed
-   (Connection refused)
-.endd
-
-If the option is unset, the default is &_/tmp/clamd_&. Thanks to David Saez for
-contributing the code for this scanner.
-
-.vitem &%cmdline%&
-.cindex "virus scanners" "command line interface"
-This is the keyword for the generic command line scanner interface. It can be
-used to attach virus scanners that are invoked from the shell. This scanner
-type takes 3 mandatory options:
-
-.olist
-The full path and name of the scanner binary, with all command line options,
-and a placeholder (&`%s`&) for the directory to scan.
-
-.next
-A regular expression to match against the STDOUT and STDERR output of the
-virus scanner. If the expression matches, a virus was found. You must make
-absolutely sure that this expression matches on &"virus found"&. This is called
-the &"trigger"& expression.
-
-.next
-Another regular expression, containing exactly one pair of parentheses, to
-match the name of the virus found in the scanners output. This is called the
-&"name"& expression.
-.endlist olist
-
-For example, Sophos Sweep reports a virus on a line like this:
-.code
-Virus 'W32/Magistr-B' found in file ./those.bat
-.endd
-For the trigger expression, we can match the phrase &"found in file"&. For the
-name expression, we want to extract the W32/Magistr-B string, so we can match
-for the single quotes left and right of it. Altogether, this makes the
-configuration setting:
-.code
-av_scanner = cmdline:\
-             /path/to/sweep -ss -all -rec -archive %s:\
-             found in file:'(.+)'
-.endd
-.vitem &%drweb%&
-.cindex "virus scanners" "DrWeb"
-The DrWeb daemon scanner (&url(https://www.sald.ru/)) interface
-takes one option,
-either a full path to a UNIX socket,
-or host and port specifiers separated by white space.
-The host may be a name or an IP address; the port is either a
-single number or a pair of numbers with a dash between.
-For example:
-.code
-av_scanner = drweb:/var/run/drwebd.sock
-av_scanner = drweb:192.168.2.20 31337
-.endd
-If you omit the argument, the default path &_/usr/local/drweb/run/drwebd.sock_&
-is used. Thanks to Alex Miller for contributing the code for this scanner.
-
-.vitem &%f-protd%&
-.cindex "virus scanners" "f-protd"
-The f-protd scanner is accessed via HTTP over TCP.
-One argument is taken, being a space-separated hostname and port number
-(or port-range).
-For example:
-.code
-av_scanner = f-protd:localhost 10200-10204
-.endd
-If you omit the argument, the default values shown above are used.
-
-.vitem &%f-prot6d%&
-.cindex "virus scanners" "f-prot6d"
-The f-prot6d scanner is accessed using the FPSCAND protocol over TCP.
-One argument is taken, being a space-separated hostname and port number.
-For example:
-.code
-av_scanner = f-prot6d:localhost 10200
-.endd
-If you omit the argument, the default values show above are used.
-
-.vitem &%fsecure%&
-.cindex "virus scanners" "F-Secure"
-The F-Secure daemon scanner (&url(https://www.f-secure.com/)) takes one
-argument which is the path to a UNIX socket. For example:
-.code
-av_scanner = fsecure:/path/to/.fsav
-.endd
-If no argument is given, the default is &_/var/run/.fsav_&. Thanks to Johan
-Thelmen for contributing the code for this scanner.
-
-.vitem &%kavdaemon%&
-.cindex "virus scanners" "Kaspersky"
-This is the scanner daemon of Kaspersky Version 4. This version of the
-Kaspersky scanner is outdated. Please upgrade (see &%aveserver%& above). This
-scanner type takes one option, which is the path to the daemon's UNIX socket.
-For example:
-.code
-av_scanner = kavdaemon:/opt/AVP/AvpCtl
-.endd
-The default path is &_/var/run/AvpCtl_&.
-
-.vitem &%mksd%&
-.cindex "virus scanners" "mksd"
-This was a daemon type scanner that is aimed mainly at Polish users,
-though some documentation was available in English.
-The history can be shown at &url(https://en.wikipedia.org/wiki/Mks_vir)
-and this appears to be a candidate for removal from Exim, unless
-we are informed of other virus scanners which use the same protocol
-to integrate.
-The only option for this scanner type is
-the maximum number of processes used simultaneously to scan the attachments,
-provided that mksd has
-been run with at least the same number of child processes. For example:
-.code
-av_scanner = mksd:2
-.endd
-You can safely omit this option (the default value is 1).
-
-.vitem &%sock%&
-.cindex "virus scanners" "simple socket-connected"
-This is a general-purpose way of talking to simple scanner daemons
-running on the local machine.
-There are four options:
-an address (which may be an IP address and port, or the path of a Unix socket),
-a commandline to send (may include a single %s which will be replaced with
-the path to the mail file to be scanned),
-an RE to trigger on from the returned data,
-and an RE to extract malware_name from the returned data.
-For example:
-.code
-av_scanner = sock:127.0.0.1 6001:%s:(SPAM|VIRUS):(.*)$
-.endd
-Note that surrounding whitespace is stripped from each option, meaning
-there is no way to specify a trailing newline.
-The socket specifier and both regular-expressions are required.
-Default for the commandline is &_%s\n_& (note this does have a trailing newline);
-specify an empty element to get this.
-
-.vitem &%sophie%&
-.cindex "virus scanners" "Sophos and Sophie"
-Sophie is a daemon that uses Sophos' &%libsavi%& library to scan for viruses.
-You can get Sophie at &url(http://sophie.sourceforge.net/). The only option
-for this scanner type is the path to the UNIX socket that Sophie uses for
-client communication. For example:
-.code
-av_scanner = sophie:/tmp/sophie
-.endd
-The default path is &_/var/run/sophie_&, so if you are using this, you can omit
-the option.
-.endlist
-
-When &%av_scanner%& is correctly set, you can use the &%malware%& condition in
-the DATA ACL. &*Note*&: You cannot use the &%malware%& condition in the MIME
-ACL.
-
-The &%av_scanner%& option is expanded each time &%malware%& is called. This
-makes it possible to use different scanners. See further below for an example.
-The &%malware%& condition caches its results, so when you use it multiple times
-for the same message, the actual scanning process is only carried out once.
-However, using expandable items in &%av_scanner%& disables this caching, in
-which case each use of the &%malware%& condition causes a new scan of the
-message.
-
-The &%malware%& condition takes a right-hand argument that is expanded before
-use and taken as a list, slash-separated by default.
-The first element can then be one of
-
-.ilist
-&"true"&, &"*"&, or &"1"&, in which case the message is scanned for viruses.
-The condition succeeds if a virus was found, and fail otherwise. This is the
-recommended usage.
-.next
-&"false"& or &"0"& or an empty string, in which case no scanning is done and
-the condition fails immediately.
-.next
-A regular expression, in which case the message is scanned for viruses. The
-condition succeeds if a virus is found and its name matches the regular
-expression. This allows you to take special actions on certain types of virus.
-Note that &"/"& characters in the RE must be doubled due to the list-processing,
-unless the separator is changed (in the usual way &<<SECTlistsepchange>>&).
-.endlist
-
-You can append a &`defer_ok`& element to the &%malware%& argument list to accept
-messages even if there is a problem with the virus scanner.
-Otherwise, such a problem causes the ACL to defer.
-
-You can append a &`tmo=<val>`& element to the &%malware%& argument list to
-specify a non-default timeout.  The default is two minutes.
-For example:
-.code
-malware = * / defer_ok / tmo=10s
-.endd
-A timeout causes the ACL to defer.
-
-.vindex "&$callout_address$&"
-When a connection is made to the scanner the expansion variable &$callout_address$&
-is set to record the actual address used.
-
-.vindex "&$malware_name$&"
-When a virus is found, the condition sets up an expansion variable called
-&$malware_name$& that contains the name of the virus. You can use it in a
-&%message%& modifier that specifies the error returned to the sender, and/or in
-logging data.
-
-Beware the interaction of Exim's &%message_size_limit%& with any size limits
-imposed by your anti-virus scanner.
-
-Here is a very simple scanning example:
-.code
-deny message = This message contains malware ($malware_name)
-     malware = *
-.endd
-The next example accepts messages when there is a problem with the scanner:
-.code
-deny message = This message contains malware ($malware_name)
-     malware = */defer_ok
-.endd
-The next example shows how to use an ACL variable to scan with both sophie and
-aveserver. It assumes you have set:
-.code
-av_scanner = $acl_m0
-.endd
-in the main Exim configuration.
-.code
-deny message = This message contains malware ($malware_name)
-     set acl_m0 = sophie
-     malware = *
-
-deny message = This message contains malware ($malware_name)
-     set acl_m0 = aveserver
-     malware = *
-.endd
-
-
-.section "Scanning with SpamAssassin and Rspamd" "SECTscanspamass"
-.cindex "content scanning" "for spam"
-.cindex "spam scanning"
-.cindex "SpamAssassin"
-.cindex "Rspamd"
-The &%spam%& ACL condition calls SpamAssassin's &%spamd%& daemon to get a spam
-score and a report for the message.
-Support is also provided for Rspamd.
-
-For more information about installation and configuration of SpamAssassin or
-Rspamd refer to their respective websites at
-&url(https://spamassassin.apache.org/) and &url(https://www.rspamd.com/)
-
-SpamAssassin can be installed with CPAN by running:
-.code
-perl -MCPAN -e 'install Mail::SpamAssassin'
-.endd
-SpamAssassin has its own set of configuration files. Please review its
-documentation to see how you can tweak it. The default installation should work
-nicely, however.
-
-.oindex "&%spamd_address%&"
-By default, SpamAssassin listens on 127.0.0.1, TCP port 783 and if you
-intend to use an instance running on the local host you do not need to set
-&%spamd_address%&. If you intend to use another host or port for SpamAssassin,
-you must set the &%spamd_address%& option in the global part of the Exim
-configuration as follows (example):
-.code
-spamd_address = 192.168.99.45 783
-.endd
-The SpamAssassin protocol relies on a TCP half-close from the client.
-If your SpamAssassin client side is running a Linux system with an
-iptables firewall, consider setting
-&%net.netfilter.nf_conntrack_tcp_timeout_close_wait%& to at least the
-timeout, Exim uses when waiting for a response from the SpamAssassin
-server (currently defaulting to 120s).  With a lower value the Linux
-connection tracking may consider your half-closed connection as dead too
-soon.
-
-
-To use Rspamd (which by default listens on all local addresses
-on TCP port 11333)
-you should add &%variant=rspamd%& after the address/port pair, for example:
-.code
-spamd_address = 127.0.0.1 11333 variant=rspamd
-.endd
-
-As of version 2.60, &%SpamAssassin%& also supports communication over UNIX
-sockets. If you want to us these, supply &%spamd_address%& with an absolute
-filename instead of an address/port pair:
-.code
-spamd_address = /var/run/spamd_socket
-.endd
-You can have multiple &%spamd%& servers to improve scalability. These can
-reside on other hardware reachable over the network. To specify multiple
-&%spamd%& servers, put multiple address/port pairs in the &%spamd_address%&
-option, separated with colons (the separator can be changed in the usual way &<<SECTlistsepchange>>&):
-.code
-spamd_address = 192.168.2.10 783 : \
-                192.168.2.11 783 : \
-                192.168.2.12 783
-.endd
-Up to 32 &%spamd%& servers are supported.
-When a server fails to respond to the connection attempt, all other
-servers are tried until one succeeds. If no server responds, the &%spam%&
-condition defers.
-
-Unix and TCP socket specifications may be mixed in any order.
-Each element of the list is a list itself, space-separated by default
-and changeable in the usual way (&<<SECTlistsepchange>>&);
-take care to not double the separator.
-
-For TCP socket specifications a host name or IP (v4 or v6, but
-subject to list-separator quoting rules) address can be used,
-and the port can be one or a dash-separated pair.
-In the latter case, the range is tried in strict order.
-
-Elements after the first for Unix sockets, or second for TCP socket,
-are options.
-The supported options are:
-.code
-pri=<priority>      Selection priority
-weight=<value>      Selection bias
-time=<start>-<end>  Use only between these times of day
-retry=<timespec>    Retry on connect fail
-tmo=<timespec>      Connection time limit
-variant=rspamd      Use Rspamd rather than SpamAssassin protocol
-.endd
-
-The &`pri`& option specifies a priority for the server within the list,
-higher values being tried first.
-The default priority is 1.
-
-The &`weight`& option specifies a selection bias.
-Within a priority set
-servers are queried in a random fashion, weighted by this value.
-The default value for selection bias is 1.
-
-Time specifications for the &`time`& option are <hour>.<minute>.<second>
-in the local time zone; each element being one or more digits.
-Either the seconds or both minutes and seconds, plus the leading &`.`&
-characters, may be omitted and will be taken as zero.
-
-Timeout specifications for the &`retry`& and &`tmo`& options
-are the usual Exim time interval standard, e.g. &`20s`& or &`1m`&.
-
-The &`tmo`& option specifies an overall timeout for communication.
-The default value is two minutes.
-
-The &`retry`& option specifies a time after which a single retry for
-a failed connect is made.
-The default is to not retry.
-
-The &%spamd_address%& variable is expanded before use if it starts with
-a dollar sign. In this case, the expansion may return a string that is
-used as the list so that multiple spamd servers can be the result of an
-expansion.
-
-.vindex "&$callout_address$&"
-When a connection is made to the server the expansion variable &$callout_address$&
-is set to record the actual address used.
-
-.section "Calling SpamAssassin from an Exim ACL" "SECID206"
-Here is a simple example of the use of the &%spam%& condition in a DATA ACL:
-.code
-deny message = This message was classified as SPAM
-     spam = joe
-.endd
-The right-hand side of the &%spam%& condition specifies a name. This is
-relevant if you have set up multiple SpamAssassin profiles. If you do not want
-to scan using a specific profile, but rather use the SpamAssassin system-wide
-default profile, you can scan for an unknown name, or simply use &"nobody"&.
-Rspamd does not use this setting. However, you must put something on the
-right-hand side.
-
-The name allows you to use per-domain or per-user antispam profiles in
-principle, but this is not straightforward in practice, because a message may
-have multiple recipients, not necessarily all in the same domain. Because the
-&%spam%& condition has to be called from a DATA-time ACL in order to be able to
-read the contents of the message, the variables &$local_part$& and &$domain$&
-are not set.
-Careful enforcement of single-recipient messages
-(e.g. by responding with defer in the recipient ACL for all recipients
-after the first),
-or the use of PRDR,
-.cindex "PRDR" "use for per-user SpamAssassin profiles"
-are needed to use this feature.
-
-The right-hand side of the &%spam%& condition is expanded before being used, so
-you can put lookups or conditions there. When the right-hand side evaluates to
-&"0"& or &"false"&, no scanning is done and the condition fails immediately.
-
-
-Scanning with SpamAssassin uses a lot of resources. If you scan every message,
-large ones may cause significant performance degradation. As most spam messages
-are quite small, it is recommended that you do not scan the big ones. For
-example:
-.code
-deny message = This message was classified as SPAM
-     condition = ${if < {$message_size}{10K}}
-     spam = nobody
-.endd
-
-The &%spam%& condition returns true if the threshold specified in the user's
-SpamAssassin profile has been matched or exceeded. If you want to use the
-&%spam%& condition for its side effects (see the variables below), you can make
-it always return &"true"& by appending &`:true`& to the username.
-
-.cindex "spam scanning" "returned variables"
-When the &%spam%& condition is run, it sets up a number of expansion
-variables.
-Except for &$spam_report$&,
-these variables are saved with the received message so are
-available for use at delivery time.
-
-.vlist
-.vitem &$spam_score$&
-The spam score of the message, for example, &"3.4"& or &"30.5"&. This is useful
-for inclusion in log or reject messages.
-
-.vitem &$spam_score_int$&
-The spam score of the message, multiplied by ten, as an integer value. For
-example &"34"& or &"305"&. It may appear to disagree with &$spam_score$&
-because &$spam_score$& is rounded and &$spam_score_int$& is truncated.
-The integer value is useful for numeric comparisons in conditions.
-
-.vitem &$spam_bar$&
-A string consisting of a number of &"+"& or &"-"& characters, representing the
-integer part of the spam score value. A spam score of 4.4 would have a
-&$spam_bar$& value of &"++++"&. This is useful for inclusion in warning
-headers, since MUAs can match on such strings. The maximum length of the
-spam bar is 50 characters.
-
-.vitem &$spam_report$&
-A multiline text table, containing the full SpamAssassin report for the
-message. Useful for inclusion in headers or reject messages.
-This variable is only usable in a DATA-time ACL.
-Beware that SpamAssassin may return non-ASCII characters, especially
-when running in country-specific locales, which are not legal
-unencoded in headers.
-
-.vitem &$spam_action$&
-For SpamAssassin either 'reject' or 'no action' depending on the
-spam score versus threshold.
-For Rspamd, the recommended action.
-
-.endlist
-
-The &%spam%& condition caches its results unless expansion in
-spamd_address was used. If you call it again with the same user name, it
-does not scan again, but rather returns the same values as before.
-
-The &%spam%& condition returns DEFER if there is any error while running
-the message through SpamAssassin or if the expansion of spamd_address
-failed. If you want to treat DEFER as FAIL (to pass on to the next ACL
-statement block), append &`/defer_ok`& to the right-hand side of the
-spam condition, like this:
-.code
-deny message = This message was classified as SPAM
-     spam    = joe/defer_ok
-.endd
-This causes messages to be accepted even if there is a problem with &%spamd%&.
-
-Here is a longer, commented example of the use of the &%spam%&
-condition:
-.code
-# put headers in all messages (no matter if spam or not)
-warn  spam = nobody:true
-      add_header = X-Spam-Score: $spam_score ($spam_bar)
-      add_header = X-Spam-Report: $spam_report
-
-# add second subject line with *SPAM* marker when message
-# is over threshold
-warn  spam = nobody
-      add_header = Subject: *SPAM* $h_Subject:
-
-# reject spam at high scores (> 12)
-deny  message = This message scored $spam_score spam points.
-      spam = nobody:true
-      condition = ${if >{$spam_score_int}{120}{1}{0}}
-.endd
-
-
-
-.section "Scanning MIME parts" "SECTscanmimepart"
-.cindex "content scanning" "MIME parts"
-.cindex "MIME content scanning"
-.oindex "&%acl_smtp_mime%&"
-.oindex "&%acl_not_smtp_mime%&"
-The &%acl_smtp_mime%& global option specifies an ACL that is called once for
-each MIME part of an SMTP message, including multipart types, in the sequence
-of their position in the message. Similarly, the &%acl_not_smtp_mime%& option
-specifies an ACL that is used for the MIME parts of non-SMTP messages. These
-options may both refer to the same ACL if you want the same processing in both
-cases.
-
-These ACLs are called (possibly many times) just before the &%acl_smtp_data%&
-ACL in the case of an SMTP message, or just before the &%acl_not_smtp%& ACL in
-the case of a non-SMTP message. However, a MIME ACL is called only if the
-message contains a &'Content-Type:'& header line. When a call to a MIME
-ACL does not yield &"accept"&, ACL processing is aborted and the appropriate
-result code is sent to the client. In the case of an SMTP message, the
-&%acl_smtp_data%& ACL is not called when this happens.
-
-You cannot use the &%malware%& or &%spam%& conditions in a MIME ACL; these can
-only be used in the DATA or non-SMTP ACLs. However, you can use the &%regex%&
-condition to match against the raw MIME part. You can also use the
-&%mime_regex%& condition to match against the decoded MIME part (see section
-&<<SECTscanregex>>&).
-
-At the start of a MIME ACL, a number of variables are set from the header
-information for the relevant MIME part. These are described below. The contents
-of the MIME part are not by default decoded into a disk file except for MIME
-parts whose content-type is &"message/rfc822"&. If you want to decode a MIME
-part into a disk file, you can use the &%decode%& condition. The general
-syntax is:
-.display
-&`decode = [/`&<&'path'&>&`/]`&<&'filename'&>
-.endd
-The right hand side is expanded before use. After expansion,
-the value can be:
-
-.olist
-&"0"& or &"false"&, in which case no decoding is done.
-.next
-The string &"default"&. In that case, the file is put in the temporary
-&"default"& directory <&'spool_directory'&>&_/scan/_&<&'message_id'&>&_/_& with
-a sequential filename consisting of the message id and a sequence number. The
-full path and name is available in &$mime_decoded_filename$& after decoding.
-.next
-A full path name starting with a slash. If the full name is an existing
-directory, it is used as a replacement for the default directory. The filename
-is then sequentially assigned. If the path does not exist, it is used as
-the full path and filename.
-.next
-If the string does not start with a slash, it is used as the
-filename, and the default path is then used.
-.endlist
-The &%decode%& condition normally succeeds. It is only false for syntax
-errors or unusual circumstances such as memory shortages. You can easily decode
-a file with its original, proposed filename using
-.code
-decode = $mime_filename
-.endd
-However, you should keep in mind that &$mime_filename$& might contain
-anything. If you place files outside of the default path, they are not
-automatically unlinked.
-
-For RFC822 attachments (these are messages attached to messages, with a
-content-type of &"message/rfc822"&), the ACL is called again in the same manner
-as for the primary message, only that the &$mime_is_rfc822$& expansion
-variable is set (see below). Attached messages are always decoded to disk
-before being checked, and the files are unlinked once the check is done.
-
-The MIME ACL supports the &%regex%& and &%mime_regex%& conditions. These can be
-used to match regular expressions against raw and decoded MIME parts,
-respectively. They are described in section &<<SECTscanregex>>&.
-
-.cindex "MIME content scanning" "returned variables"
-The following list describes all expansion variables that are
-available in the MIME ACL:
-
-.vlist
-.vitem &$mime_anomaly_level$& &&&
-       &$mime_anomaly_text$&
-.vindex &$mime_anomaly_level$&
-.vindex &$mime_anomaly_text$&
-If there are problems decoding, these variables contain information on
-the detected issue.
-
-.vitem &$mime_boundary$&
-.vindex &$mime_boundary$&
-If the current part is a multipart (see &$mime_is_multipart$& below), it should
-have a boundary string, which is stored in this variable. If the current part
-has no boundary parameter in the &'Content-Type:'& header, this variable
-contains the empty string.
-
-.vitem &$mime_charset$&
-.vindex &$mime_charset$&
-This variable contains the character set identifier, if one was found in the
-&'Content-Type:'& header. Examples for charset identifiers are:
-.code
-us-ascii
-gb2312 (Chinese)
-iso-8859-1
-.endd
-Please note that this value is not normalized, so you should do matches
-case-insensitively.
-
-.vitem &$mime_content_description$&
-.vindex &$mime_content_description$&
-This variable contains the normalized content of the &'Content-Description:'&
-header. It can contain a human-readable description of the parts content. Some
-implementations repeat the filename for attachments here, but they are usually
-only used for display purposes.
-
-.vitem &$mime_content_disposition$&
-.vindex &$mime_content_disposition$&
-This variable contains the normalized content of the &'Content-Disposition:'&
-header. You can expect strings like &"attachment"& or &"inline"& here.
-
-.vitem &$mime_content_id$&
-.vindex &$mime_content_id$&
-This variable contains the normalized content of the &'Content-ID:'& header.
-This is a unique ID that can be used to reference a part from another part.
-
-.vitem &$mime_content_size$&
-.vindex &$mime_content_size$&
-This variable is set only after the &%decode%& modifier (see above) has been
-successfully run. It contains the size of the decoded part in kilobytes. The
-size is always rounded up to full kilobytes, so only a completely empty part
-has a &$mime_content_size$& of zero.
-
-.vitem &$mime_content_transfer_encoding$&
-.vindex &$mime_content_transfer_encoding$&
-This variable contains the normalized content of the
-&'Content-transfer-encoding:'& header. This is a symbolic name for an encoding
-type. Typical values are &"base64"& and &"quoted-printable"&.
-
-.vitem &$mime_content_type$&
-.vindex &$mime_content_type$&
-If the MIME part has a &'Content-Type:'& header, this variable contains its
-value, lowercased, and without any options (like &"name"& or &"charset"&). Here
-are some examples of popular MIME types, as they may appear in this variable:
-.code
-text/plain
-text/html
-application/octet-stream
-image/jpeg
-audio/midi
-.endd
-If the MIME part has no &'Content-Type:'& header, this variable contains the
-empty string.
-
-.vitem &$mime_decoded_filename$&
-.vindex &$mime_decoded_filename$&
-This variable is set only after the &%decode%& modifier (see above) has been
-successfully run. It contains the full path and filename of the file
-containing the decoded data.
-.endlist
-
-.cindex "RFC 2047"
-.vlist
-.vitem &$mime_filename$&
-.vindex &$mime_filename$&
-This is perhaps the most important of the MIME variables. It contains a
-proposed filename for an attachment, if one was found in either the
-&'Content-Type:'& or &'Content-Disposition:'& headers. The filename will be
-RFC2047
-or RFC2231
-decoded, but no additional sanity checks are done.
- If no filename was
-found, this variable contains the empty string.
-
-.vitem &$mime_is_coverletter$&
-.vindex &$mime_is_coverletter$&
-This variable attempts to differentiate the &"cover letter"& of an e-mail from
-attached data. It can be used to clamp down on flashy or unnecessarily encoded
-content in the cover letter, while not restricting attachments at all.
-
-The variable contains 1 (true) for a MIME part believed to be part of the
-cover letter, and 0 (false) for an attachment. At present, the algorithm is as
-follows:
-
-.olist
-The outermost MIME part of a message is always a cover letter.
-
-.next
-If a multipart/alternative or multipart/related MIME part is a cover letter,
-so are all MIME subparts within that multipart.
-
-.next
-If any other multipart is a cover letter, the first subpart is a cover letter,
-and the rest are attachments.
-
-.next
-All parts contained within an attachment multipart are attachments.
-.endlist olist
-
-As an example, the following will ban &"HTML mail"& (including that sent with
-alternative plain text), while allowing HTML files to be attached. HTML
-coverletter mail attached to non-HTML coverletter mail will also be allowed:
-.code
-deny message = HTML mail is not accepted here
-!condition = $mime_is_rfc822
-condition = $mime_is_coverletter
-condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
-.endd
-
-.vitem &$mime_is_multipart$&
-.vindex &$mime_is_multipart$&
-This variable has the value 1 (true) when the current part has the main type
-&"multipart"&, for example, &"multipart/alternative"& or &"multipart/mixed"&.
-Since multipart entities only serve as containers for other parts, you may not
-want to carry out specific actions on them.
-
-.vitem &$mime_is_rfc822$&
-.vindex &$mime_is_rfc822$&
-This variable has the value 1 (true) if the current part is not a part of the
-checked message itself, but part of an attached message. Attached message
-decoding is fully recursive.
-
-.vitem &$mime_part_count$&
-.vindex &$mime_part_count$&
-This variable is a counter that is raised for each processed MIME part. It
-starts at zero for the very first part (which is usually a multipart). The
-counter is per-message, so it is reset when processing RFC822 attachments (see
-&$mime_is_rfc822$&). The counter stays set after &%acl_smtp_mime%& is
-complete, so you can use it in the DATA ACL to determine the number of MIME
-parts of a message. For non-MIME messages, this variable contains the value -1.
-.endlist
-
-
-
-.section "Scanning with regular expressions" "SECTscanregex"
-.cindex "content scanning" "with regular expressions"
-.cindex "regular expressions" "content scanning with"
-You can specify your own custom regular expression matches on the full body of
-the message, or on individual MIME parts.
-
-The &%regex%& condition takes one or more regular expressions as arguments and
-matches them against the full message (when called in the DATA ACL) or a raw
-MIME part (when called in the MIME ACL). The &%regex%& condition matches
-linewise, with a maximum line length of 32K characters. That means you cannot
-have multiline matches with the &%regex%& condition.
-
-The &%mime_regex%& condition can be called only in the MIME ACL. It matches up
-to 32K of decoded content (the whole content at once, not linewise). If the
-part has not been decoded with the &%decode%& modifier earlier in the ACL, it
-is decoded automatically when &%mime_regex%& is executed (using default path
-and filename values). If the decoded data is larger than  32K, only the first
-32K characters are checked.
-
-The regular expressions are passed as a colon-separated list. To include a
-literal colon, you must double it. Since the whole right-hand side string is
-expanded before being used, you must also escape dollar signs and backslashes
-with more backslashes, or use the &`\N`& facility to disable expansion.
-Here is a simple example that contains two regular expressions:
-.code
-deny message = contains blacklisted regex ($regex_match_string)
-     regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
-.endd
-The conditions returns true if any one of the regular expressions matches. The
-&$regex_match_string$& expansion variable is then set up and contains the
-matching regular expression.
-The expansion variables &$regex1$& &$regex2$& etc
-are set to any substrings captured by the regular expression.
-
-&*Warning*&: With large messages, these conditions can be fairly
-CPU-intensive.
-
-.ecindex IIDcosca
-
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "Adding a local scan function to Exim" "CHAPlocalscan" &&&
-         "Local scan function"
-.scindex IIDlosca "&[local_scan()]& function" "description of"
-.cindex "customizing" "input scan using C function"
-.cindex "policy control" "by local scan function"
-In these days of email worms, viruses, and ever-increasing spam, some sites
-want to apply a lot of checking to messages before accepting them.
-
-The content scanning extension (chapter &<<CHAPexiscan>>&) has facilities for
-passing messages to external virus and spam scanning software. You can also do
-a certain amount in Exim itself through string expansions and the &%condition%&
-condition in the ACL that runs after the SMTP DATA command or the ACL for
-non-SMTP messages (see chapter &<<CHAPACL>>&), but this has its limitations.
-
-To allow for further customization to a site's own requirements, there is the
-possibility of linking Exim with a private message scanning function, written
-in C. If you want to run code that is written in something other than C, you
-can of course use a little C stub to call it.
-
-The local scan function is run once for every incoming message, at the point
-when Exim is just about to accept the message.
-It can therefore be used to control non-SMTP messages from local processes as
-well as messages arriving via SMTP.
-
-Exim applies a timeout to calls of the local scan function, and there is an
-option called &%local_scan_timeout%& for setting it. The default is 5 minutes.
-Zero means &"no timeout"&.
-Exim also sets up signal handlers for SIGSEGV, SIGILL, SIGFPE, and SIGBUS
-before calling the local scan function, so that the most common types of crash
-are caught. If the timeout is exceeded or one of those signals is caught, the
-incoming message is rejected with a temporary error if it is an SMTP message.
-For a non-SMTP message, the message is dropped and Exim ends with a non-zero
-code. The incident is logged on the main and reject logs.
-
-
-
-.section "Building Exim to use a local scan function" "SECID207"
-.cindex "&[local_scan()]& function" "building Exim to use"
-To make use of the local scan function feature, you must tell Exim where your
-function is before building Exim, by setting
-both HAVE_LOCAL_SCAN and
-LOCAL_SCAN_SOURCE in your
-&_Local/Makefile_&. A recommended place to put it is in the &_Local_&
-directory, so you might set
-.code
-HAVE_LOCAL_SCAN=yes
-LOCAL_SCAN_SOURCE=Local/local_scan.c
-.endd
-for example. The function must be called &[local_scan()]&;
-.new
-the source file(s) for it should first #define LOCAL_SCAN
-and then #include "local_scan.h".
-.wen
-It is called by
-Exim after it has received a message, when the success return code is about to
-be sent. This is after all the ACLs have been run. The return code from your
-function controls whether the message is actually accepted or not. There is a
-commented template function (that just accepts the message) in the file
-_src/local_scan.c_.
-
-If you want to make use of Exim's runtime configuration file to set options
-for your &[local_scan()]& function, you must also set
-.code
-LOCAL_SCAN_HAS_OPTIONS=yes
-.endd
-in &_Local/Makefile_& (see section &<<SECTconoptloc>>& below).
-
-
-
-
-.section "API for local_scan()" "SECTapiforloc"
-.cindex "&[local_scan()]& function" "API description"
-.cindex &%dlfunc%& "API description"
-You must include this line near the start of your code:
-.code
-#define LOCAL_SCAN
-#include "local_scan.h"
-.endd
-This header file defines a number of variables and other values, and the
-prototype for the function itself. Exim is coded to use unsigned char values
-almost exclusively, and one of the things this header defines is a shorthand
-for &`unsigned char`& called &`uschar`&.
-It also makes available the following macro definitions, to simplify casting character
-strings and pointers to character strings:
-.code
-#define CS   (char *)
-#define CCS  (const char *)
-#define CSS  (char **)
-#define US   (unsigned char *)
-#define CUS  (const unsigned char *)
-#define USS  (unsigned char **)
-.endd
-The function prototype for &[local_scan()]& is:
-.code
-extern int local_scan(int fd, uschar **return_text);
-.endd
-The arguments are as follows:
-
-.ilist
-&%fd%& is a file descriptor for the file that contains the body of the message
-(the -D file). The file is open for reading and writing, but updating it is not
-recommended. &*Warning*&: You must &'not'& close this file descriptor.
-
-The descriptor is positioned at character 19 of the file, which is the first
-character of the body itself, because the first 19 characters are the message
-id followed by &`-D`& and a newline. If you rewind the file, you should use the
-macro SPOOL_DATA_START_OFFSET to reset to the start of the data, just in
-case this changes in some future version.
-.next
-&%return_text%& is an address which you can use to return a pointer to a text
-string at the end of the function. The value it points to on entry is NULL.
-.endlist
-
-The function must return an &%int%& value which is one of the following macros:
-
-.vlist
-.vitem &`LOCAL_SCAN_ACCEPT`&
-.vindex "&$local_scan_data$&"
-The message is accepted. If you pass back a string of text, it is saved with
-the message, and made available in the variable &$local_scan_data$&. No
-newlines are permitted (if there are any, they are turned into spaces) and the
-maximum length of text is 1000 characters.
-
-.vitem &`LOCAL_SCAN_ACCEPT_FREEZE`&
-This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
-queued without immediate delivery, and is frozen.
-
-.vitem &`LOCAL_SCAN_ACCEPT_QUEUE`&
-This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
-queued without immediate delivery.
-
-.vitem &`LOCAL_SCAN_REJECT`&
-The message is rejected; the returned text is used as an error message which is
-passed back to the sender and which is also logged. Newlines are permitted &--
-they cause a multiline response for SMTP rejections, but are converted to
-&`\n`& in log lines. If no message is given, &"Administrative prohibition"& is
-used.
-
-.vitem &`LOCAL_SCAN_TEMPREJECT`&
-The message is temporarily rejected; the returned text is used as an error
-message as for LOCAL_SCAN_REJECT. If no message is given, &"Temporary local
-problem"& is used.
-
-.vitem &`LOCAL_SCAN_REJECT_NOLOGHDR`&
-This behaves as LOCAL_SCAN_REJECT, except that the header of the rejected
-message is not written to the reject log. It has the effect of unsetting the
-&%rejected_header%& log selector for just this rejection. If
-&%rejected_header%& is already unset (see the discussion of the
-&%log_selection%& option in section &<<SECTlogselector>>&), this code is the
-same as LOCAL_SCAN_REJECT.
-
-.vitem &`LOCAL_SCAN_TEMPREJECT_NOLOGHDR`&
-This code is a variation of LOCAL_SCAN_TEMPREJECT in the same way that
-LOCAL_SCAN_REJECT_NOLOGHDR is a variation of LOCAL_SCAN_REJECT.
-.endlist
-
-If the message is not being received by interactive SMTP, rejections are
-reported by writing to &%stderr%& or by sending an email, as configured by the
-&%-oe%& command line options.
-
-
-
-.section "Configuration options for local_scan()" "SECTconoptloc"
-.cindex "&[local_scan()]& function" "configuration options"
-It is possible to have option settings in the main configuration file
-that set values in static variables in the &[local_scan()]& module. If you
-want to do this, you must have the line
-.code
-LOCAL_SCAN_HAS_OPTIONS=yes
-.endd
-in your &_Local/Makefile_& when you build Exim. (This line is in
-&_OS/Makefile-Default_&, commented out). Then, in the &[local_scan()]& source
-file, you must define static variables to hold the option values, and a table
-to define them.
-
-The table must be a vector called &%local_scan_options%&, of type
-&`optionlist`&. Each entry is a triplet, consisting of a name, an option type,
-and a pointer to the variable that holds the value. The entries must appear in
-alphabetical order. Following &%local_scan_options%& you must also define a
-variable called &%local_scan_options_count%& that contains the number of
-entries in the table. Here is a short example, showing two kinds of option:
-.code
-static int my_integer_option = 42;
-static uschar *my_string_option = US"a default string";
-
-optionlist local_scan_options[] = {
-  { "my_integer", opt_int,       &my_integer_option },
-  { "my_string",  opt_stringptr, &my_string_option }
-};
-
-int local_scan_options_count =
-  sizeof(local_scan_options)/sizeof(optionlist);
-.endd
-The values of the variables can now be changed from Exim's runtime
-configuration file by including a local scan section as in this example:
-.code
-begin local_scan
-my_integer = 99
-my_string = some string of text...
-.endd
-The available types of option data are as follows:
-
-.vlist
-.vitem &*opt_bool*&
-This specifies a boolean (true/false) option. The address should point to a
-variable of type &`BOOL`&, which will be set to TRUE or FALSE, which are macros
-that are defined as &"1"& and &"0"&, respectively. If you want to detect
-whether such a variable has been set at all, you can initialize it to
-TRUE_UNSET. (BOOL variables are integers underneath, so can hold more than two
-values.)
-
-.vitem &*opt_fixed*&
-This specifies a fixed point number, such as is used for load averages.
-The address should point to a variable of type &`int`&. The value is stored
-multiplied by 1000, so, for example, 1.4142 is truncated and stored as 1414.
-
-.vitem &*opt_int*&
-This specifies an integer; the address should point to a variable of type
-&`int`&. The value may be specified in any of the integer formats accepted by
-Exim.
-
-.vitem &*opt_mkint*&
-This is the same as &%opt_int%&, except that when such a value is output in a
-&%-bP%& listing, if it is an exact number of kilobytes or megabytes, it is
-printed with the suffix K or M.
-
-.vitem &*opt_octint*&
-This also specifies an integer, but the value is always interpreted as an
-octal integer, whether or not it starts with the digit zero, and it is
-always output in octal.
-
-.vitem &*opt_stringptr*&
-This specifies a string value; the address must be a pointer to a
-variable that points to a string (for example, of type &`uschar *`&).
-
-.vitem &*opt_time*&
-This specifies a time interval value. The address must point to a variable of
-type &`int`&. The value that is placed there is a number of seconds.
-.endlist
-
-If the &%-bP%& command line option is followed by &`local_scan`&, Exim prints
-out the values of all the &[local_scan()]& options.
-
-
-
-.section "Available Exim variables" "SECID208"
-.cindex "&[local_scan()]& function" "available Exim variables"
-The header &_local_scan.h_& gives you access to a number of C variables. These
-are the only ones that are guaranteed to be maintained from release to release.
-Note, however, that you can obtain the value of any Exim expansion variable,
-including &$recipients$&, by calling &'expand_string()'&. The exported
-C variables are as follows:
-
-.vlist
-.vitem &*int&~body_linecount*&
-This variable contains the number of lines in the message's body.
-It is not valid if the &%spool_files_wireformat%& option is used.
-
-.vitem &*int&~body_zerocount*&
-This variable contains the number of binary zero bytes in the message's body.
-It is not valid if the &%spool_files_wireformat%& option is used.
-
-.vitem &*unsigned&~int&~debug_selector*&
-This variable is set to zero when no debugging is taking place. Otherwise, it
-is a bitmap of debugging selectors. Two bits are identified for use in
-&[local_scan()]&; they are defined as macros:
-
-.ilist
-The &`D_v`& bit is set when &%-v%& was present on the command line. This is a
-testing option that is not privileged &-- any caller may set it. All the
-other selector bits can be set only by admin users.
-
-.next
-The &`D_local_scan`& bit is provided for use by &[local_scan()]&; it is set
-by the &`+local_scan`& debug selector. It is not included in the default set
-of debugging bits.
-.endlist ilist
-
-Thus, to write to the debugging output only when &`+local_scan`& has been
-selected, you should use code like this:
-.code
-if ((debug_selector & D_local_scan) != 0)
-  debug_printf("xxx", ...);
-.endd
-.vitem &*uschar&~*expand_string_message*&
-After a failing call to &'expand_string()'& (returned value NULL), the
-variable &%expand_string_message%& contains the error message, zero-terminated.
-
-.vitem &*header_line&~*header_list*&
-A pointer to a chain of header lines. The &%header_line%& structure is
-discussed below.
-
-.vitem &*header_line&~*header_last*&
-A pointer to the last of the header lines.
-
-.vitem &*uschar&~*headers_charset*&
-The value of the &%headers_charset%& configuration option.
-
-.vitem &*BOOL&~host_checking*&
-This variable is TRUE during a host checking session that is initiated by the
-&%-bh%& command line option.
-
-.vitem &*uschar&~*interface_address*&
-The IP address of the interface that received the message, as a string. This
-is NULL for locally submitted messages.
-
-.vitem &*int&~interface_port*&
-The port on which this message was received. When testing with the &%-bh%&
-command line option, the value of this variable is -1 unless a port has been
-specified via the &%-oMi%& option.
-
-.vitem &*uschar&~*message_id*&
-This variable contains Exim's message id for the incoming message (the value of
-&$message_exim_id$&) as a zero-terminated string.
-
-.vitem &*uschar&~*received_protocol*&
-The name of the protocol by which the message was received.
-
-.vitem &*int&~recipients_count*&
-The number of accepted recipients.
-
-.vitem &*recipient_item&~*recipients_list*&
-.cindex "recipient" "adding in local scan"
-.cindex "recipient" "removing in local scan"
-The list of accepted recipients, held in a vector of length
-&%recipients_count%&. The &%recipient_item%& structure is discussed below. You
-can add additional recipients by calling &'receive_add_recipient()'& (see
-below). You can delete recipients by removing them from the vector and
-adjusting the value in &%recipients_count%&. In particular, by setting
-&%recipients_count%& to zero you remove all recipients. If you then return the
-value &`LOCAL_SCAN_ACCEPT`&, the message is accepted, but immediately
-blackholed. To replace the recipients, you can set &%recipients_count%& to zero
-and then call &'receive_add_recipient()'& as often as needed.
-
-.vitem &*uschar&~*sender_address*&
-The envelope sender address. For bounce messages this is the empty string.
-
-.vitem &*uschar&~*sender_host_address*&
-The IP address of the sending host, as a string. This is NULL for
-locally-submitted messages.
-
-.vitem &*uschar&~*sender_host_authenticated*&
-The name of the authentication mechanism that was used, or NULL if the message
-was not received over an authenticated SMTP connection.
-
-.vitem &*uschar&~*sender_host_name*&
-The name of the sending host, if known.
-
-.vitem &*int&~sender_host_port*&
-The port on the sending host.
-
-.vitem &*BOOL&~smtp_input*&
-This variable is TRUE for all SMTP input, including BSMTP.
-
-.vitem &*BOOL&~smtp_batched_input*&
-This variable is TRUE for BSMTP input.
-
-.vitem &*int&~store_pool*&
-The contents of this variable control which pool of memory is used for new
-requests. See section &<<SECTmemhanloc>>& for details.
-.endlist
-
-
-.section "Structure of header lines" "SECID209"
-The &%header_line%& structure contains the members listed below.
-You can add additional header lines by calling the &'header_add()'& function
-(see below). You can cause header lines to be ignored (deleted) by setting
-their type to *.
-
-
-.vlist
-.vitem &*struct&~header_line&~*next*&
-A pointer to the next header line, or NULL for the last line.
-
-.vitem &*int&~type*&
-A code identifying certain headers that Exim recognizes. The codes are printing
-characters, and are documented in chapter &<<CHAPspool>>& of this manual.
-Notice in particular that any header line whose type is * is not transmitted
-with the message. This flagging is used for header lines that have been
-rewritten, or are to be removed (for example, &'Envelope-sender:'& header
-lines.) Effectively, * means &"deleted"&.
-
-.vitem &*int&~slen*&
-The number of characters in the header line, including the terminating and any
-internal newlines.
-
-.vitem &*uschar&~*text*&
-A pointer to the text of the header. It always ends with a newline, followed by
-a zero byte. Internal newlines are preserved.
-.endlist
-
-
-
-.section "Structure of recipient items" "SECID210"
-The &%recipient_item%& structure contains these members:
-
-.vlist
-.vitem &*uschar&~*address*&
-This is a pointer to the recipient address as it was received.
-
-.vitem &*int&~pno*&
-This is used in later Exim processing when top level addresses are created by
-the &%one_time%& option. It is not relevant at the time &[local_scan()]& is run
-and must always contain -1 at this stage.
-
-.vitem &*uschar&~*errors_to*&
-If this value is not NULL, bounce messages caused by failing to deliver to the
-recipient are sent to the address it contains. In other words, it overrides the
-envelope sender for this one recipient. (Compare the &%errors_to%& generic
-router option.) If a &[local_scan()]& function sets an &%errors_to%& field to
-an unqualified address, Exim qualifies it using the domain from
-&%qualify_recipient%&. When &[local_scan()]& is called, the &%errors_to%& field
-is NULL for all recipients.
-.endlist
-
-
-
-.section "Available Exim functions" "SECID211"
-.cindex "&[local_scan()]& function" "available Exim functions"
-The header &_local_scan.h_& gives you access to a number of Exim functions.
-These are the only ones that are guaranteed to be maintained from release to
-release:
-
-.vlist
-.vitem "&*pid_t&~child_open(uschar&~**argv,&~uschar&~**envp,&~int&~newumask,&&&
-       &~int&~*infdptr,&~int&~*outfdptr, &~&~BOOL&~make_leader)*&"
-
-This function creates a child process that runs the command specified by
-&%argv%&. The environment for the process is specified by &%envp%&, which can
-be NULL if no environment variables are to be passed. A new umask is supplied
-for the process in &%newumask%&.
-
-Pipes to the standard input and output of the new process are set up
-and returned to the caller via the &%infdptr%& and &%outfdptr%& arguments. The
-standard error is cloned to the standard output. If there are any file
-descriptors &"in the way"& in the new process, they are closed. If the final
-argument is TRUE, the new process is made into a process group leader.
-
-The function returns the pid of the new process, or -1 if things go wrong.
-
-.vitem &*int&~child_close(pid_t&~pid,&~int&~timeout)*&
-This function waits for a child process to terminate, or for a timeout (in
-seconds) to expire. A timeout value of zero means wait as long as it takes. The
-return value is as follows:
-
-.ilist
->= 0
-
-The process terminated by a normal exit and the value is the process
-ending status.
-
-.next
-< 0 and > &--256
-
-The process was terminated by a signal and the value is the negation of the
-signal number.
-
-.next
-&--256
-
-The process timed out.
-.next
-&--257
-
-The was some other error in wait(); &%errno%& is still set.
-.endlist
-
-.vitem &*pid_t&~child_open_exim(int&~*fd)*&
-This function provide you with a means of submitting a new message to
-Exim. (Of course, you can also call &_/usr/sbin/sendmail_& yourself if you
-want, but this packages it all up for you.) The function creates a pipe,
-forks a subprocess that is running
-.code
-exim -t -oem -oi -f <>
-.endd
-and returns to you (via the &`int *`& argument) a file descriptor for the pipe
-that is connected to the standard input. The yield of the function is the PID
-of the subprocess. You can then write a message to the file descriptor, with
-recipients in &'To:'&, &'Cc:'&, and/or &'Bcc:'& header lines.
-
-When you have finished, call &'child_close()'& to wait for the process to
-finish and to collect its ending status. A timeout value of zero is usually
-fine in this circumstance. Unless you have made a mistake with the recipient
-addresses, you should get a return code of zero.
-
-
-.vitem &*pid_t&~child_open_exim2(int&~*fd,&~uschar&~*sender,&~uschar&~&&&
-       *sender_authentication)*&
-This function is a more sophisticated version of &'child_open()'&. The command
-that it runs is:
-.display
-&`exim -t -oem -oi -f `&&'sender'&&` -oMas `&&'sender_authentication'&
-.endd
-The third argument may be NULL, in which case the &%-oMas%& option is omitted.
-
-
-.vitem &*void&~debug_printf(char&~*,&~...)*&
-This is Exim's debugging function, with arguments as for &'(printf()'&. The
-output is written to the standard error stream. If no debugging is selected,
-calls to &'debug_printf()'& have no effect. Normally, you should make calls
-conditional on the &`local_scan`& debug selector by coding like this:
-.code
-if ((debug_selector & D_local_scan) != 0)
-  debug_printf("xxx", ...);
-.endd
-
-.vitem &*uschar&~*expand_string(uschar&~*string)*&
-This is an interface to Exim's string expansion code. The return value is the
-expanded string, or NULL if there was an expansion failure.
-The C variable &%expand_string_message%& contains an error message after an
-expansion failure. If expansion does not change the string, the return value is
-the pointer to the input string. Otherwise, the return value points to a new
-block of memory that was obtained by a call to &'store_get()'&. See section
-&<<SECTmemhanloc>>& below for a discussion of memory handling.
-
-.vitem &*void&~header_add(int&~type,&~char&~*format,&~...)*&
-This function allows you to an add additional header line at the end of the
-existing ones. The first argument is the type, and should normally be a space
-character. The second argument is a format string and any number of
-substitution arguments as for &[sprintf()]&. You may include internal newlines
-if you want, and you must ensure that the string ends with a newline.
-
-.vitem "&*void&~header_add_at_position(BOOL&~after,&~uschar&~*name,&~&&&
-        BOOL&~topnot,&~int&~type,&~char&~*format, &~&~...)*&"
-This function adds a new header line at a specified point in the header
-chain. The header itself is specified as for &'header_add()'&.
-
-If &%name%& is NULL, the new header is added at the end of the chain if
-&%after%& is true, or at the start if &%after%& is false. If &%name%& is not
-NULL, the header lines are searched for the first non-deleted header that
-matches the name. If one is found, the new header is added before it if
-&%after%& is false. If &%after%& is true, the new header is added after the
-found header and any adjacent subsequent ones with the same name (even if
-marked &"deleted"&). If no matching non-deleted header is found, the &%topnot%&
-option controls where the header is added. If it is true, addition is at the
-top; otherwise at the bottom. Thus, to add a header after all the &'Received:'&
-headers, or at the top if there are no &'Received:'& headers, you could use
-.code
-header_add_at_position(TRUE, US"Received", TRUE,
-  ' ', "X-xxx: ...");
-.endd
-Normally, there is always at least one non-deleted &'Received:'& header, but
-there may not be if &%received_header_text%& expands to an empty string.
-
-
-.vitem &*void&~header_remove(int&~occurrence,&~uschar&~*name)*&
-This function removes header lines. If &%occurrence%& is zero or negative, all
-occurrences of the header are removed. If occurrence is greater than zero, that
-particular instance of the header is removed. If no header(s) can be found that
-match the specification, the function does nothing.
-
-
-.vitem "&*BOOL&~header_testname(header_line&~*hdr,&~uschar&~*name,&~&&&
-        int&~length,&~BOOL&~notdel)*&"
-This function tests whether the given header has the given name. It is not just
-a string comparison, because white space is permitted between the name and the
-colon. If the &%notdel%& argument is true, a false return is forced for all
-&"deleted"& headers; otherwise they are not treated specially. For example:
-.code
-if (header_testname(h, US"X-Spam", 6, TRUE)) ...
-.endd
-.vitem &*uschar&~*lss_b64encode(uschar&~*cleartext,&~int&~length)*&
-.cindex "base64 encoding" "functions for &[local_scan()]& use"
-This function base64-encodes a string, which is passed by address and length.
-The text may contain bytes of any value, including zero. The result is passed
-back in dynamic memory that is obtained by calling &'store_get()'&. It is
-zero-terminated.
-
-.vitem &*int&~lss_b64decode(uschar&~*codetext,&~uschar&~**cleartext)*&
-This function decodes a base64-encoded string. Its arguments are a
-zero-terminated base64-encoded string and the address of a variable that is set
-to point to the result, which is in dynamic memory. The length of the decoded
-string is the yield of the function. If the input is invalid base64 data, the
-yield is -1. A zero byte is added to the end of the output string to make it
-easy to interpret as a C string (assuming it contains no zeros of its own). The
-added zero byte is not included in the returned count.
-
-.vitem &*int&~lss_match_domain(uschar&~*domain,&~uschar&~*list)*&
-This function checks for a match in a domain list. Domains are always
-matched caselessly. The return value is one of the following:
-.display
-&`OK     `& match succeeded
-&`FAIL   `& match failed
-&`DEFER  `& match deferred
-.endd
-DEFER is usually caused by some kind of lookup defer, such as the
-inability to contact a database.
-
-.vitem "&*int&~lss_match_local_part(uschar&~*localpart,&~uschar&~*list,&~&&&
-        BOOL&~caseless)*&"
-This function checks for a match in a local part list. The third argument
-controls case-sensitivity. The return values are as for
-&'lss_match_domain()'&.
-
-.vitem "&*int&~lss_match_address(uschar&~*address,&~uschar&~*list,&~&&&
-        BOOL&~caseless)*&"
-This function checks for a match in an address list. The third argument
-controls the case-sensitivity of the local part match. The domain is always
-matched caselessly. The return values are as for &'lss_match_domain()'&.
-
-.vitem "&*int&~lss_match_host(uschar&~*host_name,&~uschar&~*host_address,&~&&&
-        uschar&~*list)*&"
-This function checks for a match in a host list. The most common usage is
-expected to be
-.code
-lss_match_host(sender_host_name, sender_host_address, ...)
-.endd
-.vindex "&$sender_host_address$&"
-An empty address field matches an empty item in the host list. If the host name
-is NULL, the name corresponding to &$sender_host_address$& is automatically
-looked up if a host name is required to match an item in the list. The return
-values are as for &'lss_match_domain()'&, but in addition, &'lss_match_host()'&
-returns ERROR in the case when it had to look up a host name, but the lookup
-failed.
-
-.vitem "&*void&~log_write(unsigned&~int&~selector,&~int&~which,&~char&~&&&
-        *format,&~...)*&"
-This function writes to Exim's log files. The first argument should be zero (it
-is concerned with &%log_selector%&). The second argument can be &`LOG_MAIN`& or
-&`LOG_REJECT`& or &`LOG_PANIC`& or the inclusive &"or"& of any combination of
-them. It specifies to which log or logs the message is written. The remaining
-arguments are a format and relevant insertion arguments. The string should not
-contain any newlines, not even at the end.
-
-
-.vitem &*void&~receive_add_recipient(uschar&~*address,&~int&~pno)*&
-This function adds an additional recipient to the message. The first argument
-is the recipient address. If it is unqualified (has no domain), it is qualified
-with the &%qualify_recipient%& domain. The second argument must always be -1.
-
-This function does not allow you to specify a private &%errors_to%& address (as
-described with the structure of &%recipient_item%& above), because it pre-dates
-the addition of that field to the structure. However, it is easy to add such a
-value afterwards. For example:
-.code
- receive_add_recipient(US"monitor@mydom.example", -1);
- recipients_list[recipients_count-1].errors_to =
-   US"postmaster@mydom.example";
-.endd
-
-.vitem &*BOOL&~receive_remove_recipient(uschar&~*recipient)*&
-This is a convenience function to remove a named recipient from the list of
-recipients. It returns true if a recipient was removed, and false if no
-matching recipient could be found. The argument must be a complete email
-address.
-.endlist
-
-
-.cindex "RFC 2047"
-.vlist
-.vitem "&*uschar&~rfc2047_decode(uschar&~*string,&~BOOL&~lencheck,&&&
-  &~uschar&~*target,&~int&~zeroval,&~int&~*lenptr, &~&~uschar&~**error)*&"
-This function decodes strings that are encoded according to RFC 2047. Typically
-these are the contents of header lines. First, each &"encoded word"& is decoded
-from the Q or B encoding into a byte-string. Then, if provided with the name of
-a charset encoding, and if the &[iconv()]& function is available, an attempt is
-made  to translate the result to the named character set. If this fails, the
-binary string is returned with an error message.
-
-The first argument is the string to be decoded. If &%lencheck%& is TRUE, the
-maximum MIME word length is enforced. The third argument is the target
-encoding, or NULL if no translation is wanted.
-
-.cindex "binary zero" "in RFC 2047 decoding"
-.cindex "RFC 2047" "binary zero in"
-If a binary zero is encountered in the decoded string, it is replaced by the
-contents of the &%zeroval%& argument. For use with Exim headers, the value must
-not be 0 because header lines are handled as zero-terminated strings.
-
-The function returns the result of processing the string, zero-terminated; if
-&%lenptr%& is not NULL, the length of the result is set in the variable to
-which it points. When &%zeroval%& is 0, &%lenptr%& should not be NULL.
-
-If an error is encountered, the function returns NULL and uses the &%error%&
-argument to return an error message. The variable pointed to by &%error%& is
-set to NULL if there is no error; it may be set non-NULL even when the function
-returns a non-NULL value if decoding was successful, but there was a problem
-with translation.
-
-
-.vitem &*int&~smtp_fflush(void)*&
-This function is used in conjunction with &'smtp_printf()'&, as described
-below.
-
-.vitem &*void&~smtp_printf(char&~*,BOOL,&~...)*&
-The arguments of this function are almost like &[printf()]&; it writes to the SMTP
-output stream. You should use this function only when there is an SMTP output
-stream, that is, when the incoming message is being received via interactive
-SMTP. This is the case when &%smtp_input%& is TRUE and &%smtp_batched_input%&
-is FALSE. If you want to test for an incoming message from another host (as
-opposed to a local process that used the &%-bs%& command line option), you can
-test the value of &%sender_host_address%&, which is non-NULL when a remote host
-is involved.
-
-If an SMTP TLS connection is established, &'smtp_printf()'& uses the TLS
-output function, so it can be used for all forms of SMTP connection.
-
-The second argument is used to request that the data be buffered
-(when TRUE) or flushed (along with any previously buffered, when FALSE).
-This is advisory only, but likely to save on system-calls and packets
-sent when a sequence of calls to the function are made.
-
-The argument was added in Exim version 4.90 - changing the API/ABI.
-Nobody noticed until 4.93 was imminent, at which point the
-ABI version number was incremented.
-
-Strings that are written by &'smtp_printf()'& from within &[local_scan()]&
-must start with an appropriate response code: 550 if you are going to return
-LOCAL_SCAN_REJECT, 451 if you are going to return
-LOCAL_SCAN_TEMPREJECT, and 250 otherwise. Because you are writing the
-initial lines of a multi-line response, the code must be followed by a hyphen
-to indicate that the line is not the final response line. You must also ensure
-that the lines you write terminate with CRLF. For example:
-.code
-smtp_printf("550-this is some extra info\r\n");
-return LOCAL_SCAN_REJECT;
-.endd
-Note that you can also create multi-line responses by including newlines in
-the data returned via the &%return_text%& argument. The added value of using
-&'smtp_printf()'& is that, for instance, you could introduce delays between
-multiple output lines.
-
-The &'smtp_printf()'& function does not return any error indication, because it
-does not
-guarantee a flush of
-pending output, and therefore does not test
-the state of the stream. (In the main code of Exim, flushing and error
-detection is done when Exim is ready for the next SMTP input command.) If
-you want to flush the output and check for an error (for example, the
-dropping of a TCP/IP connection), you can call &'smtp_fflush()'&, which has no
-arguments. It flushes the output stream, and returns a non-zero value if there
-is an error.
-
-.new
-.vitem &*void&~*store_get(int,BOOL)*&
-This function accesses Exim's internal store (memory) manager. It gets a new
-chunk of memory whose size is given by the first argument.
-The second argument should be given as TRUE if the memory will be used for
-data possibly coming from an attacker (eg. the message content),
-FALSE if it is locally-sourced.
-Exim bombs out if it ever
-runs out of memory. See the next section for a discussion of memory handling.
-.wen
-
-.vitem &*void&~*store_get_perm(int,BOOL)*&
-This function is like &'store_get()'&, but it always gets memory from the
-permanent pool. See the next section for a discussion of memory handling.
-
-.vitem &*uschar&~*string_copy(uschar&~*string)*&
-See below.
-
-.vitem &*uschar&~*string_copyn(uschar&~*string,&~int&~length)*&
-See below.
-
-.vitem &*uschar&~*string_sprintf(char&~*format,&~...)*&
-These three functions create strings using Exim's dynamic memory facilities.
-The first makes a copy of an entire string. The second copies up to a maximum
-number of characters, indicated by the second argument. The third uses a format
-and insertion arguments to create a new string. In each case, the result is a
-pointer to a new string in the current memory pool. See the next section for
-more discussion.
-.endlist
-
-
-
-.section "More about Exim's memory handling" "SECTmemhanloc"
-.cindex "&[local_scan()]& function" "memory handling"
-No function is provided for freeing memory, because that is never needed.
-The dynamic memory that Exim uses when receiving a message is automatically
-recycled if another message is received by the same process (this applies only
-to incoming SMTP connections &-- other input methods can supply only one
-message at a time). After receiving the last message, a reception process
-terminates.
-
-Because it is recycled, the normal dynamic memory cannot be used for holding
-data that must be preserved over a number of incoming messages on the same SMTP
-connection. However, Exim in fact uses two pools of dynamic memory; the second
-one is not recycled, and can be used for this purpose.
-
-If you want to allocate memory that remains available for subsequent messages
-in the same SMTP connection, you should set
-.code
-store_pool = POOL_PERM
-.endd
-before calling the function that does the allocation. There is no need to
-restore the value if you do not need to; however, if you do want to revert to
-the normal pool, you can either restore the previous value of &%store_pool%& or
-set it explicitly to POOL_MAIN.
-
-The pool setting applies to all functions that get dynamic memory, including
-&'expand_string()'&, &'store_get()'&, and the &'string_xxx()'& functions.
-There is also a convenience function called &'store_get_perm()'& that gets a
-block of memory from the permanent pool while preserving the value of
-&%store_pool%&.
-.ecindex IIDlosca
-
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "System-wide message filtering" "CHAPsystemfilter"
-.scindex IIDsysfil1 "filter" "system filter"
-.scindex IIDsysfil2 "filtering all mail"
-.scindex IIDsysfil3 "system filter"
-The previous chapters (on ACLs and the local scan function) describe checks
-that can be applied to messages before they are accepted by a host. There is
-also a mechanism for checking messages once they have been received, but before
-they are delivered. This is called the &'system filter'&.
-
-The system filter operates in a similar manner to users' filter files, but it
-is run just once per message (however many recipients the message has).
-It should not normally be used as a substitute for routing, because &%deliver%&
-commands in a system router provide new envelope recipient addresses.
-The system filter must be an Exim filter. It cannot be a Sieve filter.
-
-The system filter is run at the start of a delivery attempt, before any routing
-is done. If a message fails to be completely delivered at the first attempt,
-the system filter is run again at the start of every retry.
-If you want your filter to do something only once per message, you can make use
-of the &%first_delivery%& condition in an &%if%& command in the filter to
-prevent it happening on retries.
-
-.vindex "&$domain$&"
-.vindex "&$local_part$&"
-&*Warning*&: Because the system filter runs just once, variables that are
-specific to individual recipient addresses, such as &$local_part$& and
-&$domain$&, are not set, and the &"personal"& condition is not meaningful. If
-you want to run a centrally-specified filter for each recipient address
-independently, you can do so by setting up a suitable &(redirect)& router, as
-described in section &<<SECTperaddfil>>& below.
-
-
-.section "Specifying a system filter" "SECID212"
-.cindex "uid (user id)" "system filter"
-.cindex "gid (group id)" "system filter"
-The name of the file that contains the system filter must be specified by
-setting &%system_filter%&. If you want the filter to run under a uid and gid
-other than root, you must also set &%system_filter_user%& and
-&%system_filter_group%& as appropriate. For example:
-.code
-system_filter = /etc/mail/exim.filter
-system_filter_user = exim
-.endd
-If a system filter generates any deliveries directly to files or pipes (via the
-&%save%& or &%pipe%& commands), transports to handle these deliveries must be
-specified by setting &%system_filter_file_transport%& and
-&%system_filter_pipe_transport%&, respectively. Similarly,
-&%system_filter_reply_transport%& must be set to handle any messages generated
-by the &%reply%& command.
-
-
-.section "Testing a system filter" "SECID213"
-You can run simple tests of a system filter in the same way as for a user
-filter, but you should use &%-bF%& rather than &%-bf%&, so that features that
-are permitted only in system filters are recognized.
-
-If you want to test the combined effect of a system filter and a user filter,
-you can use both &%-bF%& and &%-bf%& on the same command line.
-
-
-
-.section "Contents of a system filter" "SECID214"
-The language used to specify system filters is the same as for users' filter
-files. It is described in the separate end-user document &'Exim's interface to
-mail filtering'&. However, there are some additional features that are
-available only in system filters; these are described in subsequent sections.
-If they are encountered in a user's filter file or when testing with &%-bf%&,
-they cause errors.
-
-.cindex "frozen messages" "manual thaw; testing in filter"
-There are two special conditions which, though available in users' filter
-files, are designed for use in system filters. The condition &%first_delivery%&
-is true only for the first attempt at delivering a message, and
-&%manually_thawed%& is true only if the message has been frozen, and
-subsequently thawed by an admin user. An explicit forced delivery counts as a
-manual thaw, but thawing as a result of the &%auto_thaw%& setting does not.
-
-&*Warning*&: If a system filter uses the &%first_delivery%& condition to
-specify an &"unseen"& (non-significant) delivery, and that delivery does not
-succeed, it will not be tried again.
-If you want Exim to retry an unseen delivery until it succeeds, you should
-arrange to set it up every time the filter runs.
-
-When a system filter finishes running, the values of the variables &$n0$& &--
-&$n9$& are copied into &$sn0$& &-- &$sn9$& and are thereby made available to
-users' filter files. Thus a system filter can, for example, set up &"scores"&
-to which users' filter files can refer.
-
-
-
-.section "Additional variable for system filters" "SECID215"
-.vindex "&$recipients$&"
-The expansion variable &$recipients$&, containing a list of all the recipients
-of the message (separated by commas and white space), is available in system
-filters. It is not available in users' filters for privacy reasons.
-
-
-
-.section "Defer, freeze, and fail commands for system filters" "SECID216"
-.cindex "freezing messages"
-.cindex "message" "freezing"
-.cindex "message" "forced failure"
-.cindex "&%fail%&" "in system filter"
-.cindex "&%freeze%& in system filter"
-.cindex "&%defer%& in system filter"
-There are three extra commands (&%defer%&, &%freeze%& and &%fail%&) which are
-always available in system filters, but are not normally enabled in users'
-filters. (See the &%allow_defer%&, &%allow_freeze%& and &%allow_fail%& options
-for the &(redirect)& router.) These commands can optionally be followed by the
-word &%text%& and a string containing an error message, for example:
-.code
-fail text "this message looks like spam to me"
-.endd
-The keyword &%text%& is optional if the next character is a double quote.
-
-The &%defer%& command defers delivery of the original recipients of the
-message. The &%fail%& command causes all the original recipients to be failed,
-and a bounce message to be created. The &%freeze%& command suspends all
-delivery attempts for the original recipients. In all cases, any new deliveries
-that are specified by the filter are attempted as normal after the filter has
-run.
-
-The &%freeze%& command is ignored if the message has been manually unfrozen and
-not manually frozen since. This means that automatic freezing by a system
-filter can be used as a way of checking out suspicious messages. If a message
-is found to be all right, manually unfreezing it allows it to be delivered.
-
-.cindex "log" "&%fail%& command log line"
-.cindex "&%fail%&" "log line; reducing"
-The text given with a fail command is used as part of the bounce message as
-well as being written to the log. If the message is quite long, this can fill
-up a lot of log space when such failures are common. To reduce the size of the
-log message, Exim interprets the text in a special way if it starts with the
-two characters &`<<`& and contains &`>>`& later. The text between these two
-strings is written to the log, and the rest of the text is used in the bounce
-message. For example:
-.code
-fail "<<filter test 1>>Your message is rejected \
-     because it contains attachments that we are \
-     not prepared to receive."
-.endd
-
-.cindex "loop" "caused by &%fail%&"
-Take great care with the &%fail%& command when basing the decision to fail on
-the contents of the message, because the bounce message will of course include
-the contents of the original message and will therefore trigger the &%fail%&
-command again (causing a mail loop) unless steps are taken to prevent this.
-Testing the &%error_message%& condition is one way to prevent this. You could
-use, for example
-.code
-if $message_body contains "this is spam" and not error_message
-then fail text "spam is not wanted here" endif
-.endd
-though of course that might let through unwanted bounce messages. The
-alternative is clever checking of the body and/or headers to detect bounces
-generated by the filter.
-
-The interpretation of a system filter file ceases after a
-&%defer%&,
-&%freeze%&, or &%fail%& command is obeyed. However, any deliveries that were
-set up earlier in the filter file are honoured, so you can use a sequence such
-as
-.code
-mail ...
-freeze
-.endd
-to send a specified message when the system filter is freezing (or deferring or
-failing) a message. The normal deliveries for the message do not, of course,
-take place.
-
-
-
-.section "Adding and removing headers in a system filter" "SECTaddremheasys"
-.cindex "header lines" "adding; in system filter"
-.cindex "header lines" "removing; in system filter"
-.cindex "filter" "header lines; adding/removing"
-Two filter commands that are available only in system filters are:
-.code
-headers add <string>
-headers remove <string>
-.endd
-The argument for the &%headers add%& is a string that is expanded and then
-added to the end of the message's headers. It is the responsibility of the
-filter maintainer to make sure it conforms to RFC 2822 syntax. Leading white
-space is ignored, and if the string is otherwise empty, or if the expansion is
-forced to fail, the command has no effect.
-
-You can use &"\n"& within the string, followed by white space, to specify
-continued header lines. More than one header may be added in one command by
-including &"\n"& within the string without any following white space. For
-example:
-.code
-headers add "X-header-1: ....\n  \
-             continuation of X-header-1 ...\n\
-             X-header-2: ...."
-.endd
-Note that the header line continuation white space after the first newline must
-be placed before the backslash that continues the input string, because white
-space after input continuations is ignored.
-
-The argument for &%headers remove%& is a colon-separated list of header names.
-This command applies only to those headers that are stored with the message;
-those that are added at delivery time (such as &'Envelope-To:'& and
-&'Return-Path:'&) cannot be removed by this means. If there is more than one
-header with the same name, they are all removed.
-
-The &%headers%& command in a system filter makes an immediate change to the set
-of header lines that was received with the message (with possible additions
-from ACL processing). Subsequent commands in the system filter operate on the
-modified set, which also forms the basis for subsequent message delivery.
-Unless further modified during routing or transporting, this set of headers is
-used for all recipients of the message.
-
-During routing and transporting, the variables that refer to the contents of
-header lines refer only to those lines that are in this set. Thus, header lines
-that are added by a system filter are visible to users' filter files and to all
-routers and transports. This contrasts with the manipulation of header lines by
-routers and transports, which is not immediate, but which instead is saved up
-until the message is actually being written (see section
-&<<SECTheadersaddrem>>&).
-
-If the message is not delivered at the first attempt, header lines that were
-added by the system filter are stored with the message, and so are still
-present at the next delivery attempt. Header lines that were removed are still
-present, but marked &"deleted"& so that they are not transported with the
-message. For this reason, it is usual to make the &%headers%& command
-conditional on &%first_delivery%& so that the set of header lines is not
-modified more than once.
-
-Because header modification in a system filter acts immediately, you have to
-use an indirect approach if you want to modify the contents of a header line.
-For example:
-.code
-headers add "Old-Subject: $h_subject:"
-headers remove "Subject"
-headers add "Subject: new subject (was: $h_old-subject:)"
-headers remove "Old-Subject"
-.endd
-
-
-
-.section "Setting an errors address in a system filter" "SECID217"
-.cindex "envelope from"
-.cindex "envelope sender"
-In a system filter, if a &%deliver%& command is followed by
-.code
-errors_to <some address>
-.endd
-in order to change the envelope sender (and hence the error reporting) for that
-delivery, any address may be specified. (In a user filter, only the current
-user's address can be set.) For example, if some mail is being monitored, you
-might use
-.code
-unseen deliver monitor@spying.example errors_to root@local.example
-.endd
-to take a copy which would not be sent back to the normal error reporting
-address if its delivery failed.
-
-
-
-.section "Per-address filtering" "SECTperaddfil"
-.vindex "&$domain$&"
-.vindex "&$local_part$&"
-In contrast to the system filter, which is run just once per message for each
-delivery attempt, it is also possible to set up a system-wide filtering
-operation that runs once for each recipient address. In this case, variables
-such as &$local_part$& and &$domain$& can be used, and indeed, the choice of
-filter file could be made dependent on them. This is an example of a router
-which implements such a filter:
-.code
-central_filter:
-  check_local_user
-  driver = redirect
-  domains = +local_domains
-  file = /central/filters/$local_part
-  no_verify
-  allow_filter
-  allow_freeze
-.endd
-The filter is run in a separate process under its own uid. Therefore, either
-&%check_local_user%& must be set (as above), in which case the filter is run as
-the local user, or the &%user%& option must be used to specify which user to
-use. If both are set, &%user%& overrides.
-
-Care should be taken to ensure that none of the commands in the filter file
-specify a significant delivery if the message is to go on to be delivered to
-its intended recipient. The router will not then claim to have dealt with the
-address, so it will be passed on to subsequent routers to be delivered in the
-normal way.
-.ecindex IIDsysfil1
-.ecindex IIDsysfil2
-.ecindex IIDsysfil3
-
-
-
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "Message processing" "CHAPmsgproc"
-.scindex IIDmesproc "message" "general processing"
-Exim performs various transformations on the sender and recipient addresses of
-all messages that it handles, and also on the messages' header lines. Some of
-these are optional and configurable, while others always take place. All of
-this processing, except rewriting as a result of routing, and the addition or
-removal of header lines while delivering, happens when a message is received,
-before it is placed on Exim's queue.
-
-Some of the automatic processing takes place by default only for
-&"locally-originated"& messages. This adjective is used to describe messages
-that are not received over TCP/IP, but instead are passed to an Exim process on
-its standard input. This includes the interactive &"local SMTP"& case that is
-set up by the &%-bs%& command line option.
-
-&*Note*&: Messages received over TCP/IP on the loopback interface (127.0.0.1
-or ::1) are not considered to be locally-originated. Exim does not treat the
-loopback interface specially in any way.
-
-If you want the loopback interface to be treated specially, you must ensure
-that there are appropriate entries in your ACLs.
-
-
-
-
-.section "Submission mode for non-local messages" "SECTsubmodnon"
-.cindex "message" "submission"
-.cindex "submission mode"
-Processing that happens automatically for locally-originated messages (unless
-&%suppress_local_fixups%& is set) can also be requested for messages that are
-received over TCP/IP. The term &"submission mode"& is used to describe this
-state. Submission mode is set by the modifier
-.code
-control = submission
-.endd
-in a MAIL, RCPT, or pre-data ACL for an incoming message (see sections
-&<<SECTACLmodi>>& and &<<SECTcontrols>>&). This makes Exim treat the message as
-a local submission, and is normally used when the source of the message is
-known to be an MUA running on a client host (as opposed to an MTA). For
-example, to set submission mode for messages originating on the IPv4 loopback
-interface, you could include the following in the MAIL ACL:
-.code
-warn  hosts = 127.0.0.1
-      control = submission
-.endd
-.cindex "&%sender_retain%& submission option"
-There are some options that can be used when setting submission mode. A slash
-is used to separate options. For example:
-.code
-control = submission/sender_retain
-.endd
-Specifying &%sender_retain%& has the effect of setting &%local_sender_retain%&
-true and &%local_from_check%& false for the current incoming message. The first
-of these allows an existing &'Sender:'& header in the message to remain, and
-the second suppresses the check to ensure that &'From:'& matches the
-authenticated sender. With this setting, Exim still fixes up messages by adding
-&'Date:'& and &'Message-ID:'& header lines if they are missing, but makes no
-attempt to check sender authenticity in header lines.
-
-When &%sender_retain%& is not set, a submission mode setting may specify a
-domain to be used when generating a &'From:'& or &'Sender:'& header line. For
-example:
-.code
-control = submission/domain=some.domain
-.endd
-The domain may be empty. How this value is used is described in sections
-&<<SECTthefrohea>>& and &<<SECTthesenhea>>&. There is also a &%name%& option
-that allows you to specify the user's full name for inclusion in a created
-&'Sender:'& or &'From:'& header line. For example:
-.code
-accept authenticated = *
-       control = submission/domain=wonderland.example/\
-                            name=${lookup {$authenticated_id} \
-                                   lsearch {/etc/exim/namelist}}
-.endd
-Because the name may contain any characters, including slashes, the &%name%&
-option must be given last. The remainder of the string is used as the name. For
-the example above, if &_/etc/exim/namelist_& contains:
-.code
-bigegg:  Humpty Dumpty
-.endd
-then when the sender has authenticated as &'bigegg'&, the generated &'Sender:'&
-line would be:
-.code
-Sender: Humpty Dumpty <bigegg@wonderland.example>
-.endd
-.cindex "return path" "in submission mode"
-By default, submission mode forces the return path to the same address as is
-used to create the &'Sender:'& header. However, if &%sender_retain%& is
-specified, the return path is also left unchanged.
-
-&*Note*&: The changes caused by submission mode take effect after the predata
-ACL. This means that any sender checks performed before the fix-ups use the
-untrusted sender address specified by the user, not the trusted sender address
-specified by submission mode. Although this might be slightly unexpected, it
-does mean that you can configure ACL checks to spot that a user is trying to
-spoof another's address.
-
-.section "Line endings" "SECTlineendings"
-.cindex "line endings"
-.cindex "carriage return"
-.cindex "linefeed"
-RFC 2821 specifies that CRLF (two characters: carriage-return, followed by
-linefeed) is the line ending for messages transmitted over the Internet using
-SMTP over TCP/IP. However, within individual operating systems, different
-conventions are used. For example, Unix-like systems use just LF, but others
-use CRLF or just CR.
-
-Exim was designed for Unix-like systems, and internally, it stores messages
-using the system's convention of a single LF as a line terminator. When
-receiving a message, all line endings are translated to this standard format.
-Originally, it was thought that programs that passed messages directly to an
-MTA within an operating system would use that system's convention. Experience
-has shown that this is not the case; for example, there are Unix applications
-that use CRLF in this circumstance. For this reason, and for compatibility with
-other MTAs, the way Exim handles line endings for all messages is now as
-follows:
-
-.ilist
-LF not preceded by CR is treated as a line ending.
-.next
-CR is treated as a line ending; if it is immediately followed by LF, the LF
-is ignored.
-.next
-The sequence &"CR, dot, CR"& does not terminate an incoming SMTP message,
-nor a local message in the state where a line containing only a dot is a
-terminator.
-.next
-If a bare CR is encountered within a header line, an extra space is added after
-the line terminator so as not to end the header line. The reasoning behind this
-is that bare CRs in header lines are most likely either to be mistakes, or
-people trying to play silly games.
-.next
-If the first header line received in a message ends with CRLF, a subsequent
-bare LF in a header line is treated in the same way as a bare CR in a header
-line.
-.endlist
-
-
-
-
-
-.section "Unqualified addresses" "SECID218"
-.cindex "unqualified addresses"
-.cindex "address" "qualification"
-By default, Exim expects every envelope address it receives from an external
-host to be fully qualified. Unqualified addresses cause negative responses to
-SMTP commands. However, because SMTP is used as a means of transporting
-messages from MUAs running on personal workstations, there is sometimes a
-requirement to accept unqualified addresses from specific hosts or IP networks.
-
-Exim has two options that separately control which hosts may send unqualified
-sender or recipient addresses in SMTP commands, namely
-&%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&. In both
-cases, if an unqualified address is accepted, it is qualified by adding the
-value of &%qualify_domain%& or &%qualify_recipient%&, as appropriate.
-
-.oindex "&%qualify_domain%&"
-.oindex "&%qualify_recipient%&"
-Unqualified addresses in header lines are automatically qualified for messages
-that are locally originated, unless the &%-bnq%& option is given on the command
-line. For messages received over SMTP, unqualified addresses in header lines
-are qualified only if unqualified addresses are permitted in SMTP commands. In
-other words, such qualification is also controlled by
-&%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&,
-
-
-
-
-.section "The UUCP From line" "SECID219"
-.cindex "&""From""& line"
-.cindex "UUCP" "&""From""& line"
-.cindex "sender" "address"
-.oindex "&%uucp_from_pattern%&"
-.oindex "&%uucp_from_sender%&"
-.cindex "envelope from"
-.cindex "envelope sender"
-.cindex "Sendmail compatibility" "&""From""& line"
-Messages that have come from UUCP (and some other applications) often begin
-with a line containing the envelope sender and a timestamp, following the word
-&"From"&. Examples of two common formats are:
-.code
-From a.oakley@berlin.mus Fri Jan  5 12:35 GMT 1996
-From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT
-.endd
-This line precedes the RFC 2822 header lines. For compatibility with Sendmail,
-Exim recognizes such lines at the start of messages that are submitted to it
-via the command line (that is, on the standard input). It does not recognize
-such lines in incoming SMTP messages, unless the sending host matches
-&%ignore_fromline_hosts%& or the &%-bs%& option was used for a local message
-and &%ignore_fromline_local%& is set. The recognition is controlled by a
-regular expression that is defined by the &%uucp_from_pattern%& option, whose
-default value matches the two common cases shown above and puts the address
-that follows &"From"& into &$1$&.
-
-.cindex "numerical variables (&$1$& &$2$& etc)" "in &""From ""& line handling"
-When the caller of Exim for a non-SMTP message that contains a &"From"& line is
-a trusted user, the message's sender address is constructed by expanding the
-contents of &%uucp_sender_address%&, whose default value is &"$1"&. This is
-then parsed as an RFC 2822 address. If there is no domain, the local part is
-qualified with &%qualify_domain%& unless it is the empty string. However, if
-the command line &%-f%& option is used, it overrides the &"From"& line.
-
-If the caller of Exim is not trusted, the &"From"& line is recognized, but the
-sender address is not changed. This is also the case for incoming SMTP messages
-that are permitted to contain &"From"& lines.
-
-Only one &"From"& line is recognized. If there is more than one, the second is
-treated as a data line that starts the body of the message, as it is not valid
-as a header line. This also happens if a &"From"& line is present in an
-incoming SMTP message from a source that is not permitted to send them.
-
-
-
-.section "Resent- header lines" "SECID220"
-.cindex "&%Resent-%& header lines"
-.cindex "header lines" "Resent-"
-RFC 2822 makes provision for sets of header lines starting with the string
-&`Resent-`& to be added to a message when it is resent by the original
-recipient to somebody else. These headers are &'Resent-Date:'&,
-&'Resent-From:'&, &'Resent-Sender:'&, &'Resent-To:'&, &'Resent-Cc:'&,
-&'Resent-Bcc:'& and &'Resent-Message-ID:'&. The RFC says:
-
-.blockquote
-&'Resent fields are strictly informational. They MUST NOT be used in the normal
-processing of replies or other such automatic actions on messages.'&
-.endblockquote
-
-This leaves things a bit vague as far as other processing actions such as
-address rewriting are concerned. Exim treats &%Resent-%& header lines as
-follows:
-
-.ilist
-A &'Resent-From:'& line that just contains the login id of the submitting user
-is automatically rewritten in the same way as &'From:'& (see below).
-.next
-If there's a rewriting rule for a particular header line, it is also applied to
-&%Resent-%& header lines of the same type. For example, a rule that rewrites
-&'From:'& also rewrites &'Resent-From:'&.
-.next
-For local messages, if &'Sender:'& is removed on input, &'Resent-Sender:'& is
-also removed.
-.next
-For a locally-submitted message,
-if there are any &%Resent-%& header lines but no &'Resent-Date:'&,
-&'Resent-From:'&, or &'Resent-Message-Id:'&, they are added as necessary. It is
-the contents of &'Resent-Message-Id:'& (rather than &'Message-Id:'&) which are
-included in log lines in this case.
-.next
-The logic for adding &'Sender:'& is duplicated for &'Resent-Sender:'& when any
-&%Resent-%& header lines are present.
-.endlist
-
-
-
-
-.section "The Auto-Submitted: header line" "SECID221"
-Whenever Exim generates an autoreply, a bounce, or a delay warning message, it
-includes the header line:
-.code
-Auto-Submitted: auto-replied
-.endd
-
-.section "The Bcc: header line" "SECID222"
-.cindex "&'Bcc:'& header line"
-If Exim is called with the &%-t%& option, to take recipient addresses from a
-message's header, it removes any &'Bcc:'& header line that may exist (after
-extracting its addresses). If &%-t%& is not present on the command line, any
-existing &'Bcc:'& is not removed.
-
-
-.section "The Date: header line" "SECID223"
-.cindex "&'Date:'& header line"
-.cindex "header lines" "Date:"
-If a locally-generated or submission-mode message has no &'Date:'& header line,
-Exim adds one, using the current date and time, unless the
-&%suppress_local_fixups%& control has been specified.
-
-.section "The Delivery-date: header line" "SECID224"
-.cindex "&'Delivery-date:'& header line"
-.oindex "&%delivery_date_remove%&"
-&'Delivery-date:'& header lines are not part of the standard RFC 2822 header
-set. Exim can be configured to add them to the final delivery of messages. (See
-the generic &%delivery_date_add%& transport option.) They should not be present
-in messages in transit. If the &%delivery_date_remove%& configuration option is
-set (the default), Exim removes &'Delivery-date:'& header lines from incoming
-messages.
-
-
-.section "The Envelope-to: header line" "SECID225"
-.cindex "&'Envelope-to:'& header line"
-.cindex "header lines" "Envelope-to:"
-.oindex "&%envelope_to_remove%&"
-&'Envelope-to:'& header lines are not part of the standard RFC 2822 header set.
-Exim can be configured to add them to the final delivery of messages. (See the
-generic &%envelope_to_add%& transport option.) They should not be present in
-messages in transit. If the &%envelope_to_remove%& configuration option is set
-(the default), Exim removes &'Envelope-to:'& header lines from incoming
-messages.
-
-
-.section "The From: header line" "SECTthefrohea"
-.cindex "&'From:'& header line"
-.cindex "header lines" "From:"
-.cindex "Sendmail compatibility" "&""From""& line"
-.cindex "message" "submission"
-.cindex "submission mode"
-If a submission-mode message does not contain a &'From:'& header line, Exim
-adds one if either of the following conditions is true:
-
-.ilist
-The envelope sender address is not empty (that is, this is not a bounce
-message). The added header line copies the envelope sender address.
-.next
-.vindex "&$authenticated_id$&"
-The SMTP session is authenticated and &$authenticated_id$& is not empty.
-.olist
-.vindex "&$qualify_domain$&"
-If no domain is specified by the submission control, the local part is
-&$authenticated_id$& and the domain is &$qualify_domain$&.
-.next
-If a non-empty domain is specified by the submission control, the local
-part is &$authenticated_id$&, and the domain is the specified domain.
-.next
-If an empty domain is specified by the submission control,
-&$authenticated_id$& is assumed to be the complete address.
-.endlist
-.endlist
-
-A non-empty envelope sender takes precedence.
-
-If a locally-generated incoming message does not contain a &'From:'& header
-line, and the &%suppress_local_fixups%& control is not set, Exim adds one
-containing the sender's address. The calling user's login name and full name
-are used to construct the address, as described in section &<<SECTconstr>>&.
-They are obtained from the password data by calling &[getpwuid()]& (but see the
-&%unknown_login%& configuration option). The address is qualified with
-&%qualify_domain%&.
-
-For compatibility with Sendmail, if an incoming, non-SMTP message has a
-&'From:'& header line containing just the unqualified login name of the calling
-user, this is replaced by an address containing the user's login name and full
-name as described in section &<<SECTconstr>>&.
-
-
-.section "The Message-ID: header line" "SECID226"
-.cindex "&'Message-ID:'& header line"
-.cindex "header lines" "Message-ID:"
-.cindex "message" "submission"
-.oindex "&%message_id_header_text%&"
-If a locally-generated or submission-mode incoming message does not contain a
-&'Message-ID:'& or &'Resent-Message-ID:'& header line, and the
-&%suppress_local_fixups%& control is not set, Exim adds a suitable header line
-to the message. If there are any &'Resent-:'& headers in the message, it
-creates &'Resent-Message-ID:'&. The id is constructed from Exim's internal
-message id, preceded by the letter E to ensure it starts with a letter, and
-followed by @ and the primary host name. Additional information can be included
-in this header line by setting the &%message_id_header_text%& and/or
-&%message_id_header_domain%& options.
-
-
-.section "The Received: header line" "SECID227"
-.cindex "&'Received:'& header line"
-.cindex "header lines" "Received:"
-A &'Received:'& header line is added at the start of every message. The
-contents are defined by the &%received_header_text%& configuration option, and
-Exim automatically adds a semicolon and a timestamp to the configured string.
-
-The &'Received:'& header is generated as soon as the message's header lines
-have been received. At this stage, the timestamp in the &'Received:'& header
-line is the time that the message started to be received. This is the value
-that is seen by the DATA ACL and by the &[local_scan()]& function.
-
-Once a message is accepted, the timestamp in the &'Received:'& header line is
-changed to the time of acceptance, which is (apart from a small delay while the
--H spool file is written) the earliest time at which delivery could start.
-
-
-.section "The References: header line" "SECID228"
-.cindex "&'References:'& header line"
-.cindex "header lines" "References:"
-Messages created by the &(autoreply)& transport include a &'References:'&
-header line. This is constructed according to the rules that are described in
-section 3.64 of RFC 2822 (which states that replies should contain such a
-header line), and section 3.14 of RFC 3834 (which states that automatic
-responses are not different in this respect). However, because some mail
-processing software does not cope well with very long header lines, no more
-than 12 message IDs are copied from the &'References:'& header line in the
-incoming message. If there are more than 12, the first one and then the final
-11 are copied, before adding the message ID of the incoming message.
-
-
-
-.section "The Return-path: header line" "SECID229"
-.cindex "&'Return-path:'& header line"
-.cindex "header lines" "Return-path:"
-.oindex "&%return_path_remove%&"
-&'Return-path:'& header lines are defined as something an MTA may insert when
-it does the final delivery of messages. (See the generic &%return_path_add%&
-transport option.) Therefore, they should not be present in messages in
-transit. If the &%return_path_remove%& configuration option is set (the
-default), Exim removes &'Return-path:'& header lines from incoming messages.
-
-
-
-.section "The Sender: header line" "SECTthesenhea"
-.cindex "&'Sender:'& header line"
-.cindex "message" "submission"
-.cindex "header lines" "Sender:"
-For a locally-originated message from an untrusted user, Exim may remove an
-existing &'Sender:'& header line, and it may add a new one. You can modify
-these actions by setting the &%local_sender_retain%& option true, the
-&%local_from_check%& option false, or by using the &%suppress_local_fixups%&
-control setting.
-
-When a local message is received from an untrusted user and
-&%local_from_check%& is true (the default), and the &%suppress_local_fixups%&
-control has not been set, a check is made to see if the address given in the
-&'From:'& header line is the correct (local) sender of the message. The address
-that is expected has the login name as the local part and the value of
-&%qualify_domain%& as the domain. Prefixes and suffixes for the local part can
-be permitted by setting &%local_from_prefix%& and &%local_from_suffix%&
-appropriately. If &'From:'& does not contain the correct sender, a &'Sender:'&
-line is added to the message.
-
-If you set &%local_from_check%& false, this checking does not occur. However,
-the removal of an existing &'Sender:'& line still happens, unless you also set
-&%local_sender_retain%& to be true. It is not possible to set both of these
-options true at the same time.
-
-.cindex "submission mode"
-By default, no processing of &'Sender:'& header lines is done for messages
-received over TCP/IP or for messages submitted by trusted users. However, when
-a message is received over TCP/IP in submission mode, and &%sender_retain%& is
-not specified on the submission control, the following processing takes place:
-
-.vindex "&$authenticated_id$&"
-First, any existing &'Sender:'& lines are removed. Then, if the SMTP session is
-authenticated, and &$authenticated_id$& is not empty, a sender address is
-created as follows:
-
-.ilist
-.vindex "&$qualify_domain$&"
-If no domain is specified by the submission control, the local part is
-&$authenticated_id$& and the domain is &$qualify_domain$&.
-.next
-If a non-empty domain is specified by the submission control, the local part
-is &$authenticated_id$&, and the domain is the specified domain.
-.next
-If an empty domain is specified by the submission control,
-&$authenticated_id$& is assumed to be the complete address.
-.endlist
-
-This address is compared with the address in the &'From:'& header line. If they
-are different, a &'Sender:'& header line containing the created address is
-added. Prefixes and suffixes for the local part in &'From:'& can be permitted
-by setting &%local_from_prefix%& and &%local_from_suffix%& appropriately.
-
-.cindex "return path" "created from &'Sender:'&"
-&*Note*&: Whenever a &'Sender:'& header line is created, the return path for
-the message (the envelope sender address) is changed to be the same address,
-except in the case of submission mode when &%sender_retain%& is specified.
-
-
-
-.section "Adding and removing header lines in routers and transports" &&&
-         "SECTheadersaddrem"
-.cindex "header lines" "adding; in router or transport"
-.cindex "header lines" "removing; in router or transport"
-When a message is delivered, the addition and removal of header lines can be
-specified in a system filter, or on any of the routers and transports that
-process the message. Section &<<SECTaddremheasys>>& contains details about
-modifying headers in a system filter. Header lines can also be added in an ACL
-as a message is received (see section &<<SECTaddheadacl>>&).
-
-In contrast to what happens in a system filter, header modifications that are
-specified on routers and transports apply only to the particular recipient
-addresses that are being processed by those routers and transports. These
-changes do not actually take place until a copy of the message is being
-transported. Therefore, they do not affect the basic set of header lines, and
-they do not affect the values of the variables that refer to header lines.
-
-&*Note*&: In particular, this means that any expansions in the configuration of
-the transport cannot refer to the modified header lines, because such
-expansions all occur before the message is actually transported.
-
-For both routers and transports, the argument of a &%headers_add%&
-option must be in the form of one or more RFC 2822 header lines, separated by
-newlines (coded as &"\n"&). For example:
-.code
-headers_add = X-added-header: added by $primary_hostname\n\
-              X-added-second: another added header line
-.endd
-Exim does not check the syntax of these added header lines.
-
-Multiple &%headers_add%& options for a single router or transport can be
-specified; the values will append to a single list of header lines.
-Each header-line is separately expanded.
-
-The argument of a &%headers_remove%& option must consist of a colon-separated
-list of header names. This is confusing, because header names themselves are
-often terminated by colons. In this case, the colons are the list separators,
-not part of the names. For example:
-.code
-headers_remove = return-receipt-to:acknowledge-to
-.endd
-
-Multiple &%headers_remove%& options for a single router or transport can be
-specified; the arguments will append to a single header-names list.
-Each item is separately expanded.
-Note that colons in complex expansions which are used to
-form all or part of a &%headers_remove%& list
-will act as list separators.
-
-When &%headers_add%& or &%headers_remove%& is specified on a router,
-items are expanded at routing time,
-and then associated with all addresses that are
-accepted by that router, and also with any new addresses that it generates. If
-an address passes through several routers as a result of aliasing or
-forwarding, the changes are cumulative.
-
-.oindex "&%unseen%&"
-However, this does not apply to multiple routers that result from the use of
-the &%unseen%& option. Any header modifications that were specified by the
-&"unseen"& router or its predecessors apply only to the &"unseen"& delivery.
-
-Addresses that end up with different &%headers_add%& or &%headers_remove%&
-settings cannot be delivered together in a batch, so a transport is always
-dealing with a set of addresses that have the same header-processing
-requirements.
-
-The transport starts by writing the original set of header lines that arrived
-with the message, possibly modified by the system filter. As it writes out
-these lines, it consults the list of header names that were attached to the
-recipient address(es) by &%headers_remove%& options in routers, and it also
-consults the transport's own &%headers_remove%& option. Header lines whose
-names are on either of these lists are not written out. If there are multiple
-instances of any listed header, they are all skipped.
-
-After the remaining original header lines have been written, new header
-lines that were specified by routers' &%headers_add%& options are written, in
-the order in which they were attached to the address. These are followed by any
-header lines specified by the transport's &%headers_add%& option.
-
-This way of handling header line modifications in routers and transports has
-the following consequences:
-
-.ilist
-The original set of header lines, possibly modified by the system filter,
-remains &"visible"&, in the sense that the &$header_$&&'xxx'& variables refer
-to it, at all times.
-.next
-Header lines that are added by a router's
-&%headers_add%& option are not accessible by means of the &$header_$&&'xxx'&
-expansion syntax in subsequent routers or the transport.
-.next
-Conversely, header lines that are specified for removal by &%headers_remove%&
-in a router remain visible to subsequent routers and the transport.
-.next
-Headers added to an address by &%headers_add%& in a router cannot be removed by
-a later router or by a transport.
-.next
-An added header can refer to the contents of an original header that is to be
-removed, even it has the same name as the added header. For example:
-.code
-headers_remove = subject
-headers_add = Subject: new subject (was: $h_subject:)
-.endd
-.endlist
-
-&*Warning*&: The &%headers_add%& and &%headers_remove%& options cannot be used
-for a &(redirect)& router that has the &%one_time%& option set.
-
-
-
-
-
-.section "Constructed addresses" "SECTconstr"
-.cindex "address" "constructed"
-.cindex "constructed address"
-When Exim constructs a sender address for a locally-generated message, it uses
-the form
-.display
-<&'user name'&>&~&~<&'login'&&`@`&&'qualify_domain'&>
-.endd
-For example:
-.code
-Zaphod Beeblebrox <zaphod@end.univ.example>
-.endd
-The user name is obtained from the &%-F%& command line option if set, or
-otherwise by looking up the calling user by &[getpwuid()]& and extracting the
-&"gecos"& field from the password entry. If the &"gecos"& field contains an
-ampersand character, this is replaced by the login name with the first letter
-upper cased, as is conventional in a number of operating systems. See the
-&%gecos_name%& option for a way to tailor the handling of the &"gecos"& field.
-The &%unknown_username%& option can be used to specify user names in cases when
-there is no password file entry.
-
-.cindex "RFC 2047"
-In all cases, the user name is made to conform to RFC 2822 by quoting all or
-parts of it if necessary. In addition, if it contains any non-printing
-characters, it is encoded as described in RFC 2047, which defines a way of
-including non-ASCII characters in header lines. The value of the
-&%headers_charset%& option specifies the name of the encoding that is used (the
-characters are assumed to be in this encoding). The setting of
-&%print_topbitchars%& controls whether characters with the top bit set (that
-is, with codes greater than 127) count as printing characters or not.
-
-
-
-.section "Case of local parts" "SECID230"
-.cindex "case of local parts"
-.cindex "local part" "case of"
-RFC 2822 states that the case of letters in the local parts of addresses cannot
-be assumed to be non-significant. Exim preserves the case of local parts of
-addresses, but by default it uses a lower-cased form when it is routing,
-because on most Unix systems, usernames are in lower case and case-insensitive
-routing is required. However, any particular router can be made to use the
-original case for local parts by setting the &%caseful_local_part%& generic
-router option.
-
-.cindex "mixed-case login names"
-If you must have mixed-case user names on your system, the best way to proceed,
-assuming you want case-independent handling of incoming email, is to set up
-your first router to convert incoming local parts in your domains to the
-correct case by means of a file lookup. For example:
-.code
-correct_case:
-  driver = redirect
-  domains = +local_domains
-  data = ${lookup{$local_part}cdb\
-              {/etc/usercased.cdb}{$value}fail}\
-              @$domain
-.endd
-For this router, the local part is forced to lower case by the default action
-(&%caseful_local_part%& is not set). The lower-cased local part is used to look
-up a new local part in the correct case. If you then set &%caseful_local_part%&
-on any subsequent routers which process your domains, they will operate on
-local parts with the correct case in a case-sensitive manner.
-
-
-
-.section "Dots in local parts" "SECID231"
-.cindex "dot" "in local part"
-.cindex "local part" "dots in"
-RFC 2822 forbids empty components in local parts. That is, an unquoted local
-part may not begin or end with a dot, nor have two consecutive dots in the
-middle. However, it seems that many MTAs do not enforce this, so Exim permits
-empty components for compatibility.
-
-
-
-.section "Rewriting addresses" "SECID232"
-.cindex "rewriting" "addresses"
-Rewriting of sender and recipient addresses, and addresses in headers, can
-happen automatically, or as the result of configuration options, as described
-in chapter &<<CHAPrewrite>>&. The headers that may be affected by this are
-&'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-To:'&, &'Sender:'&, and &'To:'&.
-
-Automatic rewriting includes qualification, as mentioned above. The other case
-in which it can happen is when an incomplete non-local domain is given. The
-routing process may cause this to be expanded into the full domain name. For
-example, a header such as
-.code
-To: hare@teaparty
-.endd
-might get rewritten as
-.code
-To: hare@teaparty.wonderland.fict.example
-.endd
-Rewriting as a result of routing is the one kind of message processing that
-does not happen at input time, as it cannot be done until the address has
-been routed.
-
-Strictly, one should not do &'any'& deliveries of a message until all its
-addresses have been routed, in case any of the headers get changed as a
-result of routing. However, doing this in practice would hold up many
-deliveries for unreasonable amounts of time, just because one address could not
-immediately be routed. Exim therefore does not delay other deliveries when
-routing of one or more addresses is deferred.
-.ecindex IIDmesproc
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "SMTP processing" "CHAPSMTP"
-.scindex IIDsmtpproc1 "SMTP" "processing details"
-.scindex IIDsmtpproc2 "LMTP" "processing details"
-Exim supports a number of different ways of using the SMTP protocol, and its
-LMTP variant, which is an interactive protocol for transferring messages into a
-closed mail store application. This chapter contains details of how SMTP is
-processed. For incoming mail, the following are available:
-
-.ilist
-SMTP over TCP/IP (Exim daemon or &'inetd'&);
-.next
-SMTP over the standard input and output (the &%-bs%& option);
-.next
-Batched SMTP on the standard input (the &%-bS%& option).
-.endlist
-
-For mail delivery, the following are available:
-
-.ilist
-SMTP over TCP/IP (the &(smtp)& transport);
-.next
-LMTP over TCP/IP (the &(smtp)& transport with the &%protocol%& option set to
-&"lmtp"&);
-.next
-LMTP over a pipe to a process running in the local host (the &(lmtp)&
-transport);
-.next
-Batched SMTP to a file or pipe (the &(appendfile)& and &(pipe)& transports with
-the &%use_bsmtp%& option set).
-.endlist
-
-&'Batched SMTP'& is the name for a process in which batches of messages are
-stored in or read from files (or pipes), in a format in which SMTP commands are
-used to contain the envelope information.
-
-
-
-.section "Outgoing SMTP and LMTP over TCP/IP" "SECToutSMTPTCP"
-.cindex "SMTP" "outgoing over TCP/IP"
-.cindex "outgoing SMTP over TCP/IP"
-.cindex "LMTP" "over TCP/IP"
-.cindex "outgoing LMTP over TCP/IP"
-.cindex "EHLO"
-.cindex "HELO"
-.cindex "SIZE option on MAIL command"
-Outgoing SMTP and LMTP over TCP/IP is implemented by the &(smtp)& transport.
-The &%protocol%& option selects which protocol is to be used, but the actual
-processing is the same in both cases.
-
-If, in response to its EHLO command, Exim is told that the SIZE
-parameter is supported, it adds SIZE=<&'n'&> to each subsequent MAIL
-command. The value of <&'n'&> is the message size plus the value of the
-&%size_addition%& option (default 1024) to allow for additions to the message
-such as per-transport header lines, or changes made in a
-.cindex "transport" "filter"
-.cindex "filter" "transport filter"
-transport filter. If &%size_addition%& is set negative, the use of SIZE is
-suppressed.
-
-If the remote server advertises support for PIPELINING, Exim uses the
-pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets
-required for the transaction.
-
-If the remote server advertises support for the STARTTLS command, and Exim
-was built to support TLS encryption, it tries to start a TLS session unless the
-server matches &%hosts_avoid_tls%&. See chapter &<<CHAPTLS>>& for more details.
-Either a match in that or &%hosts_verify_avoid_tls%& apply when the transport
-is called for verification.
-
-If the remote server advertises support for the AUTH command, Exim scans
-the authenticators configuration for any suitable client settings, as described
-in chapter &<<CHAPSMTPAUTH>>&.
-
-.cindex "carriage return"
-.cindex "linefeed"
-Responses from the remote host are supposed to be terminated by CR followed by
-LF. However, there are known to be hosts that do not send CR characters, so in
-order to be able to interwork with such hosts, Exim treats LF on its own as a
-line terminator.
-
-If a message contains a number of different addresses, all those with the same
-characteristics (for example, the same envelope sender) that resolve to the
-same set of hosts, in the same order, are sent in a single SMTP transaction,
-even if they are for different domains, unless there are more than the setting
-of the &%max_rcpt%&s option in the &(smtp)& transport allows, in which case
-they are split into groups containing no more than &%max_rcpt%&s addresses
-each. If &%remote_max_parallel%& is greater than one, such groups may be sent
-in parallel sessions. The order of hosts with identical MX values is not
-significant when checking whether addresses can be batched in this way.
-
-When the &(smtp)& transport suffers a temporary failure that is not
-message-related, Exim updates its transport-specific database, which contains
-records indexed by host name that remember which messages are waiting for each
-particular host. It also updates the retry database with new retry times.
-
-.cindex "hints database" "retry keys"
-Exim's retry hints are based on host name plus IP address, so if one address of
-a multi-homed host is broken, it will soon be skipped most of the time.
-See the next section for more detail about error handling.
-
-.cindex "SMTP" "passed connection"
-.cindex "SMTP" "batching over TCP/IP"
-When a message is successfully delivered over a TCP/IP SMTP connection, Exim
-looks in the hints database for the transport to see if there are any queued
-messages waiting for the host to which it is connected. If it finds one, it
-creates a new Exim process using the &%-MC%& option (which can only be used by
-a process running as root or the Exim user) and passes the TCP/IP socket to it
-so that it can deliver another message using the same socket. The new process
-does only those deliveries that are routed to the connected host, and may in
-turn pass the socket on to a third process, and so on.
-
-The &%connection_max_messages%& option of the &(smtp)& transport can be used to
-limit the number of messages sent down a single TCP/IP connection.
-
-.cindex "asterisk" "after IP address"
-The second and subsequent messages delivered down an existing connection are
-identified in the main log by the addition of an asterisk after the closing
-square bracket of the IP address.
-
-
-
-
-.section "Errors in outgoing SMTP" "SECToutSMTPerr"
-.cindex "error" "in outgoing SMTP"
-.cindex "SMTP" "errors in outgoing"
-.cindex "host" "error"
-Three different kinds of error are recognized for outgoing SMTP: host errors,
-message errors, and recipient errors.
-
-.vlist
-.vitem "&*Host errors*&"
-A host error is not associated with a particular message or with a
-particular recipient of a message. The host errors are:
-
-.ilist
-Connection refused or timed out,
-.next
-Any error response code on connection,
-.next
-Any error response code to EHLO or HELO,
-.next
-Loss of connection at any time, except after &"."&,
-.next
-I/O errors at any time,
-.next
-Timeouts during the session, other than in response to MAIL, RCPT or
-the &"."& at the end of the data.
-.endlist ilist
-
-For a host error, a permanent error response on connection, or in response to
-EHLO, causes all addresses routed to the host to be failed. Any other host
-error causes all addresses to be deferred, and retry data to be created for the
-host. It is not tried again, for any message, until its retry time arrives. If
-the current set of addresses are not all delivered in this run (to some
-alternative host), the message is added to the list of those waiting for this
-host, so if it is still undelivered when a subsequent successful delivery is
-made to the host, it will be sent down the same SMTP connection.
-
-.vitem "&*Message errors*&"
-.cindex "message" "error"
-A message error is associated with a particular message when sent to a
-particular host, but not with a particular recipient of the message. The
-message errors are:
-
-.ilist
-Any error response code to MAIL, DATA, or the &"."& that terminates
-the data,
-.next
-Timeout after MAIL,
-.next
-Timeout or loss of connection after the &"."& that terminates the data. A
-timeout after the DATA command itself is treated as a host error, as is loss of
-connection at any other time.
-.endlist ilist
-
-For a message error, a permanent error response (5&'xx'&) causes all addresses
-to be failed, and a delivery error report to be returned to the sender. A
-temporary error response (4&'xx'&), or one of the timeouts, causes all
-addresses to be deferred. Retry data is not created for the host, but instead,
-a retry record for the combination of host plus message id is created. The
-message is not added to the list of those waiting for this host. This ensures
-that the failing message will not be sent to this host again until the retry
-time arrives. However, other messages that are routed to the host are not
-affected, so if it is some property of the message that is causing the error,
-it will not stop the delivery of other mail.
-
-If the remote host specified support for the SIZE parameter in its response
-to EHLO, Exim adds SIZE=&'nnn'& to the MAIL command, so an
-over-large message will cause a message error because the error arrives as a
-response to MAIL.
-
-.vitem "&*Recipient errors*&"
-.cindex "recipient" "error"
-A recipient error is associated with a particular recipient of a message. The
-recipient errors are:
-
-.ilist
-Any error response to RCPT,
-.next
-Timeout after RCPT.
-.endlist
-
-For a recipient error, a permanent error response (5&'xx'&) causes the
-recipient address to be failed, and a bounce message to be returned to the
-sender. A temporary error response (4&'xx'&) or a timeout causes the failing
-address to be deferred, and routing retry data to be created for it. This is
-used to delay processing of the address in subsequent queue runs, until its
-routing retry time arrives. This applies to all messages, but because it
-operates only in queue runs, one attempt will be made to deliver a new message
-to the failing address before the delay starts to operate. This ensures that,
-if the failure is really related to the message rather than the recipient
-(&"message too big for this recipient"& is a possible example), other messages
-have a chance of getting delivered. If a delivery to the address does succeed,
-the retry information gets cleared, so all stuck messages get tried again, and
-the retry clock is reset.
-
-The message is not added to the list of those waiting for this host. Use of the
-host for other messages is unaffected, and except in the case of a timeout,
-other recipients are processed independently, and may be successfully delivered
-in the current SMTP session. After a timeout it is of course impossible to
-proceed with the session, so all addresses get deferred. However, those other
-than the one that failed do not suffer any subsequent retry delays. Therefore,
-if one recipient is causing trouble, the others have a chance of getting
-through when a subsequent delivery attempt occurs before the failing
-recipient's retry time.
-.endlist
-
-In all cases, if there are other hosts (or IP addresses) available for the
-current set of addresses (for example, from multiple MX records), they are
-tried in this run for any undelivered addresses, subject of course to their
-own retry data. In other words, recipient error retry data does not take effect
-until the next delivery attempt.
-
-Some hosts have been observed to give temporary error responses to every
-MAIL command at certain times (&"insufficient space"& has been seen). It
-would be nice if such circumstances could be recognized, and defer data for the
-host itself created, but this is not possible within the current Exim design.
-What actually happens is that retry data for every (host, message) combination
-is created.
-
-The reason that timeouts after MAIL and RCPT are treated specially is that
-these can sometimes arise as a result of the remote host's verification
-procedures. Exim makes this assumption, and treats them as if a temporary error
-response had been received. A timeout after &"."& is treated specially because
-it is known that some broken implementations fail to recognize the end of the
-message if the last character of the last line is a binary zero. Thus, it is
-helpful to treat this case as a message error.
-
-Timeouts at other times are treated as host errors, assuming a problem with the
-host, or the connection to it. If a timeout after MAIL, RCPT,
-or &"."& is really a connection problem, the assumption is that at the next try
-the timeout is likely to occur at some other point in the dialogue, causing it
-then to be treated as a host error.
-
-There is experimental evidence that some MTAs drop the connection after the
-terminating &"."& if they do not like the contents of the message for some
-reason, in contravention of the RFC, which indicates that a 5&'xx'& response
-should be given. That is why Exim treats this case as a message rather than a
-host error, in order not to delay other messages to the same host.
-
-
-
-
-.section "Incoming SMTP messages over TCP/IP" "SECID233"
-.cindex "SMTP" "incoming over TCP/IP"
-.cindex "incoming SMTP over TCP/IP"
-.cindex "inetd"
-.cindex "daemon"
-Incoming SMTP messages can be accepted in one of two ways: by running a
-listening daemon, or by using &'inetd'&. In the latter case, the entry in
-&_/etc/inetd.conf_& should be like this:
-.code
-smtp stream tcp nowait exim /opt/exim/bin/exim in.exim -bs
-.endd
-Exim distinguishes between this case and the case of a locally running user
-agent using the &%-bs%& option by checking whether or not the standard input is
-a socket. When it is, either the port must be privileged (less than 1024), or
-the caller must be root or the Exim user. If any other user passes a socket
-with an unprivileged port number, Exim prints a message on the standard error
-stream and exits with an error code.
-
-By default, Exim does not make a log entry when a remote host connects or
-disconnects (either via the daemon or &'inetd'&), unless the disconnection is
-unexpected. It can be made to write such log entries by setting the
-&%smtp_connection%& log selector.
-
-.cindex "carriage return"
-.cindex "linefeed"
-Commands from the remote host are supposed to be terminated by CR followed by
-LF. However, there are known to be hosts that do not send CR characters. In
-order to be able to interwork with such hosts, Exim treats LF on its own as a
-line terminator.
-Furthermore, because common code is used for receiving messages from all
-sources, a CR on its own is also interpreted as a line terminator. However, the
-sequence &"CR, dot, CR"& does not terminate incoming SMTP data.
-
-.cindex "EHLO" "invalid data"
-.cindex "HELO" "invalid data"
-One area that sometimes gives rise to problems concerns the EHLO or
-HELO commands. Some clients send syntactically invalid versions of these
-commands, which Exim rejects by default. (This is nothing to do with verifying
-the data that is sent, so &%helo_verify_hosts%& is not relevant.) You can tell
-Exim not to apply a syntax check by setting &%helo_accept_junk_hosts%& to
-match the broken hosts that send invalid commands.
-
-.cindex "SIZE option on MAIL command"
-.cindex "MAIL" "SIZE option"
-The amount of disk space available is checked whenever SIZE is received on
-a MAIL command, independently of whether &%message_size_limit%& or
-&%check_spool_space%& is configured, unless &%smtp_check_spool_space%& is set
-false. A temporary error is given if there is not enough space. If
-&%check_spool_space%& is set, the check is for that amount of space plus the
-value given with SIZE, that is, it checks that the addition of the incoming
-message will not reduce the space below the threshold.
-
-When a message is successfully received, Exim includes the local message id in
-its response to the final &"."& that terminates the data. If the remote host
-logs this text it can help with tracing what has happened to a message.
-
-The Exim daemon can limit the number of simultaneous incoming connections it is
-prepared to handle (see the &%smtp_accept_max%& option). It can also limit the
-number of simultaneous incoming connections from a single remote host (see the
-&%smtp_accept_max_per_host%& option). Additional connection attempts are
-rejected using the SMTP temporary error code 421.
-
-The Exim daemon does not rely on the SIGCHLD signal to detect when a
-subprocess has finished, as this can get lost at busy times. Instead, it looks
-for completed subprocesses every time it wakes up. Provided there are other
-things happening (new incoming calls, starts of queue runs), completed
-processes will be noticed and tidied away. On very quiet systems you may
-sometimes see a &"defunct"& Exim process hanging about. This is not a problem;
-it will be noticed when the daemon next wakes up.
-
-When running as a daemon, Exim can reserve some SMTP slots for specific hosts,
-and can also be set up to reject SMTP calls from non-reserved hosts at times of
-high system load &-- for details see the &%smtp_accept_reserve%&,
-&%smtp_load_reserve%&, and &%smtp_reserve_hosts%& options. The load check
-applies in both the daemon and &'inetd'& cases.
-
-Exim normally starts a delivery process for each message received, though this
-can be varied by means of the &%-odq%& command line option and the
-&%queue_only%&, &%queue_only_file%&, and &%queue_only_load%& options. The
-number of simultaneously running delivery processes started in this way from
-SMTP input can be limited by the &%smtp_accept_queue%& and
-&%smtp_accept_queue_per_connection%& options. When either limit is reached,
-subsequently received messages are just put on the input queue without starting
-a delivery process.
-
-The controls that involve counts of incoming SMTP calls (&%smtp_accept_max%&,
-&%smtp_accept_queue%&, &%smtp_accept_reserve%&) are not available when Exim is
-started up from the &'inetd'& daemon, because in that case each connection is
-handled by an entirely independent Exim process. Control by load average is,
-however, available with &'inetd'&.
-
-Exim can be configured to verify addresses in incoming SMTP commands as they
-are received. See chapter &<<CHAPACL>>& for details. It can also be configured
-to rewrite addresses at this time &-- before any syntax checking is done. See
-section &<<SECTrewriteS>>&.
-
-Exim can also be configured to limit the rate at which a client host submits
-MAIL and RCPT commands in a single SMTP session. See the
-&%smtp_ratelimit_hosts%& option.
-
-
-
-.section "Unrecognized SMTP commands" "SECID234"
-.cindex "SMTP" "unrecognized commands"
-If Exim receives more than &%smtp_max_unknown_commands%& unrecognized SMTP
-commands during a single SMTP connection, it drops the connection after sending
-the error response to the last command. The default value for
-&%smtp_max_unknown_commands%& is 3. This is a defence against some kinds of
-abuse that subvert web servers into making connections to SMTP ports; in these
-circumstances, a number of non-SMTP lines are sent first.
-
-
-.section "Syntax and protocol errors in SMTP commands" "SECID235"
-.cindex "SMTP" "syntax errors"
-.cindex "SMTP" "protocol errors"
-A syntax error is detected if an SMTP command is recognized, but there is
-something syntactically wrong with its data, for example, a malformed email
-address in a RCPT command. Protocol errors include invalid command
-sequencing such as RCPT before MAIL. If Exim receives more than
-&%smtp_max_synprot_errors%& such commands during a single SMTP connection, it
-drops the connection after sending the error response to the last command. The
-default value for &%smtp_max_synprot_errors%& is 3. This is a defence against
-broken clients that loop sending bad commands (yes, it has been seen).
-
-
-
-.section "Use of non-mail SMTP commands" "SECID236"
-.cindex "SMTP" "non-mail commands"
-The &"non-mail"& SMTP commands are those other than MAIL, RCPT, and
-DATA. Exim counts such commands, and drops the connection if there are too
-many of them in a single SMTP session. This action catches some
-denial-of-service attempts and things like repeated failing AUTHs, or a mad
-client looping sending EHLO. The global option &%smtp_accept_max_nonmail%&
-defines what &"too many"& means. Its default value is 10.
-
-When a new message is expected, one occurrence of RSET is not counted. This
-allows a client to send one RSET between messages (this is not necessary,
-but some clients do it). Exim also allows one uncounted occurrence of HELO
-or EHLO, and one occurrence of STARTTLS between messages. After
-starting up a TLS session, another EHLO is expected, and so it too is not
-counted.
-
-The first occurrence of AUTH in a connection, or immediately following
-STARTTLS is also not counted. Otherwise, all commands other than MAIL,
-RCPT, DATA, and QUIT are counted.
-
-You can control which hosts are subject to the limit set by
-&%smtp_accept_max_nonmail%& by setting
-&%smtp_accept_max_nonmail_hosts%&. The default value is &`*`&, which makes
-the limit apply to all hosts. This option means that you can exclude any
-specific badly-behaved hosts that you have to live with.
-
-
-
-
-.section "The VRFY and EXPN commands" "SECID237"
-When Exim receives a VRFY or EXPN command on a TCP/IP connection, it
-runs the ACL specified by &%acl_smtp_vrfy%& or &%acl_smtp_expn%& (as
-appropriate) in order to decide whether the command should be accepted or not.
-
-.cindex "VRFY" "processing"
-When no ACL is defined for VRFY, or if it rejects without
-setting an explicit response code, the command is accepted
-(with a 252 SMTP response code)
-in order to support awkward clients that do a VRFY before every RCPT.
-When VRFY is accepted, it runs exactly the same code as when Exim is
-called with the &%-bv%& option, and returns 250/451/550
-SMTP response codes.
-
-.cindex "EXPN" "processing"
-If no ACL for EXPN is defined, the command is rejected.
-When EXPN is accepted, a single-level expansion of the address is done.
-EXPN is treated as an &"address test"& (similar to the &%-bt%& option) rather
-than a verification (the &%-bv%& option). If an unqualified local part is given
-as the argument to EXPN, it is qualified with &%qualify_domain%&. Rejections
-of VRFY and EXPN commands are logged on the main and reject logs, and
-VRFY verification failures are logged on the main log for consistency with
-RCPT failures.
-
-
-
-.section "The ETRN command" "SECTETRN"
-.cindex "ETRN" "processing"
-RFC 1985 describes an SMTP command called ETRN that is designed to
-overcome the security problems of the TURN command (which has fallen into
-disuse). When Exim receives an ETRN command on a TCP/IP connection, it runs
-the ACL specified by &%acl_smtp_etrn%& in order to decide whether the command
-should be accepted or not. If no ACL is defined, the command is rejected.
-
-The ETRN command is concerned with &"releasing"& messages that are awaiting
-delivery to certain hosts. As Exim does not organize its message queue by host,
-the only form of ETRN that is supported by default is the one where the
-text starts with the &"#"& prefix, in which case the remainder of the text is
-specific to the SMTP server. A valid ETRN command causes a run of Exim with
-the &%-R%& option to happen, with the remainder of the ETRN text as its
-argument. For example,
-.code
-ETRN #brigadoon
-.endd
-runs the command
-.code
-exim -R brigadoon
-.endd
-which causes a delivery attempt on all messages with undelivered addresses
-containing the text &"brigadoon"&. When &%smtp_etrn_serialize%& is set (the
-default), Exim prevents the simultaneous execution of more than one queue run
-for the same argument string as a result of an ETRN command. This stops
-a misbehaving client from starting more than one queue runner at once.
-
-.cindex "hints database" "ETRN serialization"
-Exim implements the serialization by means of a hints database in which a
-record is written whenever a process is started by ETRN, and deleted when
-the process completes. However, Exim does not keep the SMTP session waiting for
-the ETRN process to complete. Once ETRN is accepted, the client is sent
-a &"success"& return code. Obviously there is scope for hints records to get
-left lying around if there is a system or program crash. To guard against this,
-Exim ignores any records that are more than six hours old.
-
-.oindex "&%smtp_etrn_command%&"
-For more control over what ETRN does, the &%smtp_etrn_command%& option can
-used. This specifies a command that is run whenever ETRN is received,
-whatever the form of its argument. For
-example:
-.code
-smtp_etrn_command = /etc/etrn_command $domain \
-                    $sender_host_address
-.endd
-.vindex "&$domain$&"
-The string is split up into arguments which are independently expanded. The
-expansion variable &$domain$& is set to the argument of the ETRN command,
-and no syntax checking is done on the contents of this argument. Exim does not
-wait for the command to complete, so its status code is not checked. Exim runs
-under its own uid and gid when receiving incoming SMTP, so it is not possible
-for it to change them before running the command.
-
-
-
-.section "Incoming local SMTP" "SECID238"
-.cindex "SMTP" "local incoming"
-Some user agents use SMTP to pass messages to their local MTA using the
-standard input and output, as opposed to passing the envelope on the command
-line and writing the message to the standard input. This is supported by the
-&%-bs%& option. This form of SMTP is handled in the same way as incoming
-messages over TCP/IP (including the use of ACLs), except that the envelope
-sender given in a MAIL command is ignored unless the caller is trusted. In
-an ACL you can detect this form of SMTP input by testing for an empty host
-identification. It is common to have this as the first line in the ACL that
-runs for RCPT commands:
-.code
-accept hosts = :
-.endd
-This accepts SMTP messages from local processes without doing any other tests.
-
-
-
-.section "Outgoing batched SMTP" "SECTbatchSMTP"
-.cindex "SMTP" "batched outgoing"
-.cindex "batched SMTP output"
-Both the &(appendfile)& and &(pipe)& transports can be used for handling
-batched SMTP. Each has an option called &%use_bsmtp%& which causes messages to
-be output in BSMTP format. No SMTP responses are possible for this form of
-delivery. All it is doing is using SMTP commands as a way of transmitting the
-envelope along with the message.
-
-The message is written to the file or pipe preceded by the SMTP commands
-MAIL and RCPT, and followed by a line containing a single dot. Lines in
-the message that start with a dot have an extra dot added. The SMTP command
-HELO is not normally used. If it is required, the &%message_prefix%& option
-can be used to specify it.
-
-Because &(appendfile)& and &(pipe)& are both local transports, they accept only
-one recipient address at a time by default. However, you can arrange for them
-to handle several addresses at once by setting the &%batch_max%& option. When
-this is done for BSMTP, messages may contain multiple RCPT commands. See
-chapter &<<CHAPbatching>>& for more details.
-
-.vindex "&$host$&"
-When one or more addresses are routed to a BSMTP transport by a router that
-sets up a host list, the name of the first host on the list is available to the
-transport in the variable &$host$&. Here is an example of such a transport and
-router:
-.code
-begin routers
-route_append:
-  driver = manualroute
-  transport = smtp_appendfile
-  route_list = domain.example  batch.host.example
-
-begin transports
-smtp_appendfile:
-  driver = appendfile
-  directory = /var/bsmtp/$host
-  batch_max = 1000
-  use_bsmtp
-  user = exim
-.endd
-This causes messages addressed to &'domain.example'& to be written in BSMTP
-format to &_/var/bsmtp/batch.host.example_&, with only a single copy of each
-message (unless there are more than 1000 recipients).
-
-
-
-.section "Incoming batched SMTP" "SECTincomingbatchedSMTP"
-.cindex "SMTP" "batched incoming"
-.cindex "batched SMTP input"
-The &%-bS%& command line option causes Exim to accept one or more messages by
-reading SMTP on the standard input, but to generate no responses. If the caller
-is trusted, the senders in the MAIL commands are believed; otherwise the
-sender is always the caller of Exim. Unqualified senders and receivers are not
-rejected (there seems little point) but instead just get qualified. HELO
-and EHLO act as RSET; VRFY, EXPN, ETRN and  HELP, act
-as NOOP; QUIT quits.
-
-Minimal policy checking is done for BSMTP input. Only the non-SMTP
-ACL is run in the same way as for non-SMTP local input.
-
-If an error is detected while reading a message, including a missing &"."& at
-the end, Exim gives up immediately. It writes details of the error to the
-standard output in a stylized way that the calling program should be able to
-make some use of automatically, for example:
-.code
-554 Unexpected end of file
-Transaction started in line 10
-Error detected in line 14
-.endd
-It writes a more verbose version, for human consumption, to the standard error
-file, for example:
-.code
-An error was detected while processing a file of BSMTP input.
-The error message was:
-
-501 '>' missing at end of address
-
-The SMTP transaction started in line 10.
-The error was detected in line 12.
-The SMTP command at fault was:
-
-rcpt to:<malformed@in.com.plete
-
-1 previous message was successfully processed.
-The rest of the batch was abandoned.
-.endd
-The return code from Exim is zero only if there were no errors. It is 1 if some
-messages were accepted before an error was detected, and 2 if no messages were
-accepted.
-.ecindex IIDsmtpproc1
-.ecindex IIDsmtpproc2
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "Customizing bounce and warning messages" "CHAPemsgcust" &&&
-         "Customizing messages"
-When a message fails to be delivered, or remains in the queue for more than a
-configured amount of time, Exim sends a message to the original sender, or
-to an alternative configured address. The text of these messages is built into
-the code of Exim, but it is possible to change it, either by adding a single
-string, or by replacing each of the paragraphs by text supplied in a file.
-
-The &'From:'& and &'To:'& header lines are automatically generated; you can
-cause a &'Reply-To:'& line to be added by setting the &%errors_reply_to%&
-option. Exim also adds the line
-.code
-Auto-Submitted: auto-generated
-.endd
-to all warning and bounce messages,
-
-
-.section "Customizing bounce messages" "SECID239"
-.cindex "customizing" "bounce message"
-.cindex "bounce message" "customizing"
-If &%bounce_message_text%& is set, its contents are included in the default
-message immediately after &"This message was created automatically by mail
-delivery software."& The string is not expanded. It is not used if
-&%bounce_message_file%& is set.
-
-When &%bounce_message_file%& is set, it must point to a template file for
-constructing error messages. The file consists of a series of text items,
-separated by lines consisting of exactly four asterisks. If the file cannot be
-opened, default text is used and a message is written to the main and panic
-logs. If any text item in the file is empty, default text is used for that
-item.
-
-.vindex "&$bounce_recipient$&"
-.vindex "&$bounce_return_size_limit$&"
-Each item of text that is read from the file is expanded, and there are two
-expansion variables which can be of use here: &$bounce_recipient$& is set to
-the recipient of an error message while it is being created, and
-&$bounce_return_size_limit$& contains the value of the &%return_size_limit%&
-option, rounded to a whole number.
-
-The items must appear in the file in the following order:
-
-.ilist
-The first item is included in the headers, and should include at least a
-&'Subject:'& header. Exim does not check the syntax of these headers.
-.next
-The second item forms the start of the error message. After it, Exim lists the
-failing addresses with their error messages.
-.next
-The third item is used to introduce any text from pipe transports that is to be
-returned to the sender. It is omitted if there is no such text.
-.next
-The fourth, fifth and sixth items will be ignored and may be empty.
-The fields exist for back-compatibility
-.endlist
-
-The default state (&%bounce_message_file%& unset) is equivalent to the
-following file, in which the sixth item is empty. The &'Subject:'& and some
-other lines have been split in order to fit them on the page:
-.code
-Subject: Mail delivery failed
-  ${if eq{$sender_address}{$bounce_recipient}
-  {: returning message to sender}}
-****
-This message was created automatically by mail delivery software.
-
-A message ${if eq{$sender_address}{$bounce_recipient}
-  {that you sent }{sent by
-
-<$sender_address>
-
-}}could not be delivered to all of its recipients.
-This is a permanent error. The following address(es) failed:
-****
-The following text was generated during the delivery attempt(s):
-****
------- This is a copy of the message, including all the headers.
-  ------
-****
------- The body of the message is $message_size characters long;
-  only the first
------- $bounce_return_size_limit or so are included here.
-****
-.endd
-.section "Customizing warning messages" "SECTcustwarn"
-.cindex "customizing" "warning message"
-.cindex "warning of delay" "customizing the message"
-The option &%warn_message_file%& can be pointed at a template file for use when
-warnings about message delays are created. In this case there are only three
-text sections:
-
-.ilist
-The first item is included in the headers, and should include at least a
-&'Subject:'& header. Exim does not check the syntax of these headers.
-.next
-The second item forms the start of the warning message. After it, Exim lists
-the delayed addresses.
-.next
-The third item then ends the message.
-.endlist
-
-The default state is equivalent to the following file, except that some lines
-have been split here, in order to fit them on the page:
-.code
-Subject: Warning: message $message_exim_id delayed
-  $warn_message_delay
-****
-This message was created automatically by mail delivery software.
-
-A message ${if eq{$sender_address}{$warn_message_recipients}
-{that you sent }{sent by
-
-<$sender_address>
-
-}}has not been delivered to all of its recipients after
-more than $warn_message_delay in the queue on $primary_hostname.
-
-The message identifier is:     $message_exim_id
-The subject of the message is: $h_subject
-The date of the message is:    $h_date
-
-The following address(es) have not yet been delivered:
-****
-No action is required on your part. Delivery attempts will
-continue for some time, and this warning may be repeated at
-intervals if the message remains undelivered. Eventually the
-mail delivery software will give up, and when that happens,
-the message will be returned to you.
-.endd
-.vindex "&$warn_message_delay$&"
-.vindex "&$warn_message_recipients$&"
-However, in the default state the subject and date lines are omitted if no
-appropriate headers exist. During the expansion of this file,
-&$warn_message_delay$& is set to the delay time in one of the forms &"<&'n'&>
-minutes"& or &"<&'n'&> hours"&, and &$warn_message_recipients$& contains a list
-of recipients for the warning message. There may be more than one if there are
-multiple addresses with different &%errors_to%& settings on the routers that
-handled them.
-
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "Some common configuration settings" "CHAPcomconreq"
-This chapter discusses some configuration settings that seem to be fairly
-common. More examples and discussion can be found in the Exim book.
-
-
-
-.section "Sending mail to a smart host" "SECID240"
-.cindex "smart host" "example router"
-If you want to send all mail for non-local domains to a &"smart host"&, you
-should replace the default &(dnslookup)& router with a router which does the
-routing explicitly:
-.code
-send_to_smart_host:
-  driver = manualroute
-  route_list = !+local_domains smart.host.name
-  transport = remote_smtp
-.endd
-You can use the smart host's IP address instead of the name if you wish.
-If you are using Exim only to submit messages to a smart host, and not for
-receiving incoming messages, you can arrange for it to do the submission
-synchronously by setting the &%mua_wrapper%& option (see chapter
-&<<CHAPnonqueueing>>&).
-
-
-
-
-.section "Using Exim to handle mailing lists" "SECTmailinglists"
-.cindex "mailing lists"
-Exim can be used to run simple mailing lists, but for large and/or complicated
-requirements, the use of additional specialized mailing list software such as
-Majordomo or Mailman is recommended.
-
-The &(redirect)& router can be used to handle mailing lists where each list
-is maintained in a separate file, which can therefore be managed by an
-independent manager. The &%domains%& router option can be used to run these
-lists in a separate domain from normal mail. For example:
-.code
-lists:
-  driver = redirect
-  domains = lists.example
-  file = /usr/lists/$local_part
-  forbid_pipe
-  forbid_file
-  errors_to = $local_part-request@lists.example
-  no_more
-.endd
-This router is skipped for domains other than &'lists.example'&. For addresses
-in that domain, it looks for a file that matches the local part. If there is no
-such file, the router declines, but because &%no_more%& is set, no subsequent
-routers are tried, and so the whole delivery fails.
-
-The &%forbid_pipe%& and &%forbid_file%& options prevent a local part from being
-expanded into a filename or a pipe delivery, which is usually inappropriate in
-a mailing list.
-
-.oindex "&%errors_to%&"
-The &%errors_to%& option specifies that any delivery errors caused by addresses
-taken from a mailing list are to be sent to the given address rather than the
-original sender of the message. However, before acting on this, Exim verifies
-the error address, and ignores it if verification fails.
-
-For example, using the configuration above, mail sent to
-&'dicts@lists.example'& is passed on to those addresses contained in
-&_/usr/lists/dicts_&, with error reports directed to
-&'dicts-request@lists.example'&, provided that this address can be verified.
-There could be a file called &_/usr/lists/dicts-request_& containing
-the address(es) of this particular list's manager(s), but other approaches,
-such as setting up an earlier router (possibly using the &%local_part_prefix%&
-or &%local_part_suffix%& options) to handle addresses of the form
-&%owner-%&&'xxx'& or &%xxx-%&&'request'&, are also possible.
-
-
-
-.section "Syntax errors in mailing lists" "SECID241"
-.cindex "mailing lists" "syntax errors in"
-If an entry in redirection data contains a syntax error, Exim normally defers
-delivery of the original address. That means that a syntax error in a mailing
-list holds up all deliveries to the list. This may not be appropriate when a
-list is being maintained automatically from data supplied by users, and the
-addresses are not rigorously checked.
-
-If the &%skip_syntax_errors%& option is set, the &(redirect)& router just skips
-entries that fail to parse, noting the incident in the log. If in addition
-&%syntax_errors_to%& is set to a verifiable address, a message is sent to it
-whenever a broken address is skipped. It is usually appropriate to set
-&%syntax_errors_to%& to the same address as &%errors_to%&.
-
-
-
-.section "Re-expansion of mailing lists" "SECID242"
-.cindex "mailing lists" "re-expansion of"
-Exim remembers every individual address to which a message has been delivered,
-in order to avoid duplication, but it normally stores only the original
-recipient addresses with a message. If all the deliveries to a mailing list
-cannot be done at the first attempt, the mailing list is re-expanded when the
-delivery is next tried. This means that alterations to the list are taken into
-account at each delivery attempt, so addresses that have been added to
-the list since the message arrived will therefore receive a copy of the
-message, even though it pre-dates their subscription.
-
-If this behaviour is felt to be undesirable, the &%one_time%& option can be set
-on the &(redirect)& router. If this is done, any addresses generated by the
-router that fail to deliver at the first attempt are added to the message as
-&"top level"& addresses, and the parent address that generated them is marked
-&"delivered"&. Thus, expansion of the mailing list does not happen again at the
-subsequent delivery attempts. The disadvantage of this is that if any of the
-failing addresses are incorrect, correcting them in the file has no effect on
-pre-existing messages.
-
-The original top-level address is remembered with each of the generated
-addresses, and is output in any log messages. However, any intermediate parent
-addresses are not recorded. This makes a difference to the log only if the
-&%all_parents%& selector is set, but for mailing lists there is normally only
-one level of expansion anyway.
-
-
-
-.section "Closed mailing lists" "SECID243"
-.cindex "mailing lists" "closed"
-The examples so far have assumed open mailing lists, to which anybody may
-send mail. It is also possible to set up closed lists, where mail is accepted
-from specified senders only. This is done by making use of the generic
-&%senders%& option to restrict the router that handles the list.
-
-The following example uses the same file as a list of recipients and as a list
-of permitted senders. It requires three routers:
-.code
-lists_request:
-  driver = redirect
-  domains = lists.example
-  local_part_suffix = -request
-  file = /usr/lists/$local_part$local_part_suffix
-  no_more
-
-lists_post:
-  driver = redirect
-  domains = lists.example
-  senders = ${if exists {/usr/lists/$local_part}\
-             {lsearch;/usr/lists/$local_part}{*}}
-  file = /usr/lists/$local_part
-  forbid_pipe
-  forbid_file
-  errors_to = $local_part-request@lists.example
-  no_more
-
-lists_closed:
-  driver = redirect
-  domains = lists.example
-  allow_fail
-  data = :fail: $local_part@lists.example is a closed mailing list
-.endd
-All three routers have the same &%domains%& setting, so for any other domains,
-they are all skipped. The first router runs only if the local part ends in
-&%-request%&. It handles messages to the list manager(s) by means of an open
-mailing list.
-
-The second router runs only if the &%senders%& precondition is satisfied. It
-checks for the existence of a list that corresponds to the local part, and then
-checks that the sender is on the list by means of a linear search. It is
-necessary to check for the existence of the file before trying to search it,
-because otherwise Exim thinks there is a configuration error. If the file does
-not exist, the expansion of &%senders%& is *, which matches all senders. This
-means that the router runs, but because there is no list, declines, and
-&%no_more%& ensures that no further routers are run. The address fails with an
-&"unrouteable address"& error.
-
-The third router runs only if the second router is skipped, which happens when
-a mailing list exists, but the sender is not on it. This router forcibly fails
-the address, giving a suitable error message.
-
-
-
-
-.section "Variable Envelope Return Paths (VERP)" "SECTverp"
-.cindex "VERP"
-.cindex "Variable Envelope Return Paths"
-.cindex "envelope from"
-.cindex "envelope sender"
-Variable Envelope Return Paths &-- see &url(https://cr.yp.to/proto/verp.txt) &--
-are a way of helping mailing list administrators discover which subscription
-address is the cause of a particular delivery failure. The idea is to encode
-the original recipient address in the outgoing envelope sender address, so that
-if the message is forwarded by another host and then subsequently bounces, the
-original recipient can be extracted from the recipient address of the bounce.
-
-.oindex &%errors_to%&
-.oindex &%return_path%&
-Envelope sender addresses can be modified by Exim using two different
-facilities: the &%errors_to%& option on a router (as shown in previous mailing
-list examples), or the &%return_path%& option on a transport. The second of
-these is effective only if the message is successfully delivered to another
-host; it is not used for errors detected on the local host (see the description
-of &%return_path%& in chapter &<<CHAPtransportgeneric>>&). Here is an example
-of the use of &%return_path%& to implement VERP on an &(smtp)& transport:
-.code
-verp_smtp:
-  driver = smtp
-  max_rcpt = 1
-  return_path = \
-    ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
-      {$1-request+$local_part=$domain@your.dom.example}fail}
-.endd
-This has the effect of rewriting the return path (envelope sender) on outgoing
-SMTP messages, if the local part of the original return path ends in
-&"-request"&, and the domain is &'your.dom.example'&. The rewriting inserts the
-local part and domain of the recipient into the return path. Suppose, for
-example, that a message whose return path has been set to
-&'somelist-request@your.dom.example'& is sent to
-&'subscriber@other.dom.example'&. In the transport, the return path is
-rewritten as
-.code
-somelist-request+subscriber=other.dom.example@your.dom.example
-.endd
-.vindex "&$local_part$&"
-For this to work, you must tell Exim to send multiple copies of messages that
-have more than one recipient, so that each copy has just one recipient. This is
-achieved by setting &%max_rcpt%& to 1. Without this, a single copy of a message
-might be sent to several different recipients in the same domain, in which case
-&$local_part$& is not available in the transport, because it is not unique.
-
-Unless your host is doing nothing but mailing list deliveries, you should
-probably use a separate transport for the VERP deliveries, so as not to use
-extra resources in making one-per-recipient copies for other deliveries. This
-can easily be done by expanding the &%transport%& option in the router:
-.code
-dnslookup:
-  driver = dnslookup
-  domains = ! +local_domains
-  transport = \
-    ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
-      {verp_smtp}{remote_smtp}}
-  no_more
-.endd
-If you want to change the return path using &%errors_to%& in a router instead
-of using &%return_path%& in the transport, you need to set &%errors_to%& on all
-routers that handle mailing list addresses. This will ensure that all delivery
-errors, including those detected on the local host, are sent to the VERP
-address.
-
-On a host that does no local deliveries and has no manual routing, only the
-&(dnslookup)& router needs to be changed. A special transport is not needed for
-SMTP deliveries. Every mailing list recipient has its own return path value,
-and so Exim must hand them to the transport one at a time. Here is an example
-of a &(dnslookup)& router that implements VERP:
-.code
-verp_dnslookup:
-  driver = dnslookup
-  domains = ! +local_domains
-  transport = remote_smtp
-  errors_to = \
-    ${if match {$return_path}{^(.+?)-request@your.dom.example\$}}
-     {$1-request+$local_part=$domain@your.dom.example}fail}
-  no_more
-.endd
-Before you start sending out messages with VERPed return paths, you must also
-configure Exim to accept the bounce messages that come back to those paths.
-Typically this is done by setting a &%local_part_suffix%& option for a
-router, and using this to route the messages to wherever you want to handle
-them.
-
-The overhead incurred in using VERP depends very much on the size of the
-message, the number of recipient addresses that resolve to the same remote
-host, and the speed of the connection over which the message is being sent. If
-a lot of addresses resolve to the same host and the connection is slow, sending
-a separate copy of the message for each address may take substantially longer
-than sending a single copy with many recipients (for which VERP cannot be
-used).
-
-
-
-
-
-
-.section "Virtual domains" "SECTvirtualdomains"
-.cindex "virtual domains"
-.cindex "domain" "virtual"
-The phrase &'virtual domain'& is unfortunately used with two rather different
-meanings:
-
-.ilist
-A domain for which there are no real mailboxes; all valid local parts are
-aliases for other email addresses. Common examples are organizational
-top-level domains and &"vanity"& domains.
-.next
-One of a number of independent domains that are all handled by the same host,
-with mailboxes on that host, but where the mailbox owners do not necessarily
-have login accounts on that host.
-.endlist
-
-The first usage is probably more common, and does seem more &"virtual"& than
-the second. This kind of domain can be handled in Exim with a straightforward
-aliasing router. One approach is to create a separate alias file for each
-virtual domain. Exim can test for the existence of the alias file to determine
-whether the domain exists. The &(dsearch)& lookup type is useful here, leading
-to a router of this form:
-.code
-virtual:
-  driver = redirect
-  domains = dsearch;/etc/mail/virtual
-  data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain_data}}
-  no_more
-.endd
-.new
-The &%domains%& option specifies that the router is to be skipped, unless there
-is a file in the &_/etc/mail/virtual_& directory whose name is the same as the
-domain that is being processed.
-The &(dsearch)& lookup used results in an untainted version of &$domain$&
-being placed into the &$domain_data$& variable.
-.wen
-
-When the router runs, it looks up the local
-part in the file to find a new address (or list of addresses). The &%no_more%&
-setting ensures that if the lookup fails (leading to &%data%& being an empty
-string), Exim gives up on the address without trying any subsequent routers.
-
-This one router can handle all the virtual domains because the alias filenames
-follow a fixed pattern. Permissions can be arranged so that appropriate people
-can edit the different alias files. A successful aliasing operation results in
-a new envelope recipient address, which is then routed from scratch.
-
-The other kind of &"virtual"& domain can also be handled in a straightforward
-way. One approach is to create a file for each domain containing a list of
-valid local parts, and use it in a router like this:
-.code
-my_domains:
-  driver = accept
-  domains = dsearch;/etc/mail/domains
-  local_parts = lsearch;/etc/mail/domains/$domain
-  transport = my_mailboxes
-.endd
-The address is accepted if there is a file for the domain, and the local part
-can be found in the file. The &%domains%& option is used to check for the
-file's existence because &%domains%& is tested before the &%local_parts%&
-option (see section &<<SECTrouprecon>>&). You cannot use &%require_files%&,
-because that option is tested after &%local_parts%&. The transport is as
-follows:
-.code
-my_mailboxes:
-  driver = appendfile
-  file = /var/mail/$domain/$local_part
-  user = mail
-.endd
-This uses a directory of mailboxes for each domain. The &%user%& setting is
-required, to specify which uid is to be used for writing to the mailboxes.
-
-The configuration shown here is just one example of how you might support this
-requirement. There are many other ways this kind of configuration can be set
-up, for example, by using a database instead of separate files to hold all the
-information about the domains.
-
-
-
-.section "Multiple user mailboxes" "SECTmulbox"
-.cindex "multiple mailboxes"
-.cindex "mailbox" "multiple"
-.cindex "local part" "prefix"
-.cindex "local part" "suffix"
-Heavy email users often want to operate with multiple mailboxes, into which
-incoming mail is automatically sorted. A popular way of handling this is to
-allow users to use multiple sender addresses, so that replies can easily be
-identified. Users are permitted to add prefixes or suffixes to their local
-parts for this purpose. The wildcard facility of the generic router options
-&%local_part_prefix%& and &%local_part_suffix%& can be used for this. For
-example, consider this router:
-.code
-userforward:
-  driver = redirect
-  check_local_user
-  file = $home/.forward
-  local_part_suffix = -*
-  local_part_suffix_optional
-  allow_filter
-.endd
-.vindex "&$local_part_suffix$&"
-It runs a user's &_.forward_& file for all local parts of the form
-&'username-*'&. Within the filter file the user can distinguish different
-cases by testing the variable &$local_part_suffix$&. For example:
-.code
-if $local_part_suffix contains -special then
-save /home/$local_part/Mail/special
-endif
-.endd
-If the filter file does not exist, or does not deal with such addresses, they
-fall through to subsequent routers, and, assuming no subsequent use of the
-&%local_part_suffix%& option is made, they presumably fail. Thus, users have
-control over which suffixes are valid.
-
-Alternatively, a suffix can be used to trigger the use of a different
-&_.forward_& file &-- which is the way a similar facility is implemented in
-another MTA:
-.code
-userforward:
-  driver = redirect
-  check_local_user
-  file = $home/.forward$local_part_suffix
-  local_part_suffix = -*
-  local_part_suffix_optional
-  allow_filter
-.endd
-If there is no suffix, &_.forward_& is used; if the suffix is &'-special'&, for
-example, &_.forward-special_& is used. Once again, if the appropriate file
-does not exist, or does not deal with the address, it is passed on to
-subsequent routers, which could, if required, look for an unqualified
-&_.forward_& file to use as a default.
-
-
-
-.section "Simplified vacation processing" "SECID244"
-.cindex "vacation processing"
-The traditional way of running the &'vacation'& program is for a user to set up
-a pipe command in a &_.forward_& file
-(see section &<<SECTspecitredli>>& for syntax details).
-This is prone to error by inexperienced users. There are two features of Exim
-that can be used to make this process simpler for users:
-
-.ilist
-A local part prefix such as &"vacation-"& can be specified on a router which
-can cause the message to be delivered directly to the &'vacation'& program, or
-alternatively can use Exim's &(autoreply)& transport. The contents of a user's
-&_.forward_& file are then much simpler. For example:
-.code
-spqr, vacation-spqr
-.endd
-.next
-The &%require_files%& generic router option can be used to trigger a
-vacation delivery by checking for the existence of a certain file in the
-user's home directory. The &%unseen%& generic option should also be used, to
-ensure that the original delivery also proceeds. In this case, all the user has
-to do is to create a file called, say, &_.vacation_&, containing a vacation
-message.
-.endlist
-
-Another advantage of both these methods is that they both work even when the
-use of arbitrary pipes by users is locked out.
-
-
-
-.section "Taking copies of mail" "SECID245"
-.cindex "message" "copying every"
-Some installations have policies that require archive copies of all messages to
-be made. A single copy of each message can easily be taken by an appropriate
-command in a system filter, which could, for example, use a different file for
-each day's messages.
-
-There is also a shadow transport mechanism that can be used to take copies of
-messages that are successfully delivered by local transports, one copy per
-delivery. This could be used, &'inter alia'&, to implement automatic
-notification of delivery by sites that insist on doing such things.
-
-
-
-.section "Intermittently connected hosts" "SECID246"
-.cindex "intermittently connected hosts"
-It has become quite common (because it is cheaper) for hosts to connect to the
-Internet periodically rather than remain connected all the time. The normal
-arrangement is that mail for such hosts accumulates on a system that is
-permanently connected.
-
-Exim was designed for use on permanently connected hosts, and so it is not
-particularly well-suited to use in an intermittently connected environment.
-Nevertheless there are some features that can be used.
-
-
-.section "Exim on the upstream server host" "SECID247"
-It is tempting to arrange for incoming mail for the intermittently connected
-host to remain in Exim's queue until the client connects. However, this
-approach does not scale very well. Two different kinds of waiting message are
-being mixed up in the same queue &-- those that cannot be delivered because of
-some temporary problem, and those that are waiting for their destination host
-to connect. This makes it hard to manage the queue, as well as wasting
-resources, because each queue runner scans the entire queue.
-
-A better approach is to separate off those messages that are waiting for an
-intermittently connected host. This can be done by delivering these messages
-into local files in batch SMTP, &"mailstore"&, or other envelope-preserving
-format, from where they are transmitted by other software when their
-destination connects. This makes it easy to collect all the mail for one host
-in a single directory, and to apply local timeout rules on a per-message basis
-if required.
-
-On a very small scale, leaving the mail on Exim's queue can be made to work. If
-you are doing this, you should configure Exim with a long retry period for the
-intermittent host. For example:
-.code
-cheshire.wonderland.fict.example    *   F,5d,24h
-.endd
-This stops a lot of failed delivery attempts from occurring, but Exim remembers
-which messages it has queued up for that host. Once the intermittent host comes
-online, forcing delivery of one message (either by using the &%-M%& or &%-R%&
-options, or by using the ETRN SMTP command (see section &<<SECTETRN>>&)
-causes all the queued up messages to be delivered, often down a single SMTP
-connection. While the host remains connected, any new messages get delivered
-immediately.
-
-If the connecting hosts do not have fixed IP addresses, that is, if a host is
-issued with a different IP address each time it connects, Exim's retry
-mechanisms on the holding host get confused, because the IP address is normally
-used as part of the key string for holding retry information. This can be
-avoided by unsetting &%retry_include_ip_address%& on the &(smtp)& transport.
-Since this has disadvantages for permanently connected hosts, it is best to
-arrange a separate transport for the intermittently connected ones.
-
-
-
-.section "Exim on the intermittently connected client host" "SECID248"
-The value of &%smtp_accept_queue_per_connection%& should probably be
-increased, or even set to zero (that is, disabled) on the intermittently
-connected host, so that all incoming messages down a single connection get
-delivered immediately.
-
-.cindex "SMTP" "passed connection"
-.cindex "SMTP" "multiple deliveries"
-.cindex "multiple SMTP deliveries"
-.cindex "first pass routing"
-Mail waiting to be sent from an intermittently connected host will probably
-not have been routed, because without a connection DNS lookups are not
-possible. This means that if a normal queue run is done at connection time,
-each message is likely to be sent in a separate SMTP session. This can be
-avoided by starting the queue run with a command line option beginning with
-&%-qq%& instead of &%-q%&. In this case, the queue is scanned twice. In the
-first pass, routing is done but no deliveries take place. The second pass is a
-normal queue run; since all the messages have been previously routed, those
-destined for the same host are likely to get sent as multiple deliveries in a
-single SMTP connection.
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "Using Exim as a non-queueing client" "CHAPnonqueueing" &&&
-         "Exim as a non-queueing client"
-.cindex "client, non-queueing"
-.cindex "smart host" "suppressing queueing"
-On a personal computer, it is a common requirement for all
-email to be sent to a &"smart host"&. There are plenty of MUAs that can be
-configured to operate that way, for all the popular operating systems.
-However, there are some MUAs for Unix-like systems that cannot be so
-configured: they submit messages using the command line interface of
-&_/usr/sbin/sendmail_&. Furthermore, utility programs such as &'cron'& submit
-messages this way.
-
-If the personal computer runs continuously, there is no problem, because it can
-run a conventional MTA that handles delivery to the smart host, and deal with
-any delays via its queueing mechanism. However, if the computer does not run
-continuously or runs different operating systems at different times, queueing
-email is not desirable.
-
-There is therefore a requirement for something that can provide the
-&_/usr/sbin/sendmail_& interface but deliver messages to a smart host without
-any queueing or retrying facilities. Furthermore, the delivery to the smart
-host should be synchronous, so that if it fails, the sending MUA is immediately
-informed. In other words, we want something that extends an MUA that submits
-to a local MTA via the command line so that it behaves like one that submits
-to a remote smart host using TCP/SMTP.
-
-There are a number of applications (for example, there is one called &'ssmtp'&)
-that do this job. However, people have found them to be lacking in various
-ways. For instance, you might want to allow aliasing and forwarding to be done
-before sending a message to the smart host.
-
-Exim already had the necessary infrastructure for doing this job. Just a few
-tweaks were needed to make it behave as required, though it is somewhat of an
-overkill to use a fully-featured MTA for this purpose.
-
-.oindex "&%mua_wrapper%&"
-There is a Boolean global option called &%mua_wrapper%&, defaulting false.
-Setting &%mua_wrapper%& true causes Exim to run in a special mode where it
-assumes that it is being used to &"wrap"& a command-line MUA in the manner
-just described. As well as setting &%mua_wrapper%&, you also need to provide a
-compatible router and transport configuration. Typically there will be just one
-router and one transport, sending everything to a smart host.
-
-When run in MUA wrapping mode, the behaviour of Exim changes in the
-following ways:
-
-.ilist
-A daemon cannot be run, nor will Exim accept incoming messages from &'inetd'&.
-In other words, the only way to submit messages is via the command line.
-.next
-Each message is synchronously delivered as soon as it is received (&%-odi%& is
-assumed). All queueing options (&%queue_only%&, &%queue_smtp_domains%&,
-&%control%& in an ACL, etc.) are quietly ignored. The Exim reception process
-does not finish until the delivery attempt is complete. If the delivery is
-successful, a zero return code is given.
-.next
-Address redirection is permitted, but the final routing for all addresses must
-be to the same remote transport, and to the same list of hosts. Furthermore,
-the return address (envelope sender) must be the same for all recipients, as
-must any added or deleted header lines. In other words, it must be possible to
-deliver the message in a single SMTP transaction, however many recipients there
-are.
-.next
-If these conditions are not met, or if routing any address results in a
-failure or defer status, or if Exim is unable to deliver all the recipients
-successfully to one of the smart hosts, delivery of the entire message fails.
-.next
-Because no queueing is allowed, all failures are treated as permanent; there
-is no distinction between 4&'xx'& and 5&'xx'& SMTP response codes from the
-smart host. Furthermore, because only a single yes/no response can be given to
-the caller, it is not possible to deliver to some recipients and not others. If
-there is an error (temporary or permanent) for any recipient, all are failed.
-.next
-If more than one smart host is listed, Exim will try another host after a
-connection failure or a timeout, in the normal way. However, if this kind of
-failure happens for all the hosts, the delivery fails.
-.next
-When delivery fails, an error message is written to the standard error stream
-(as well as to Exim's log), and Exim exits to the caller with a return code
-value 1. The message is expunged from Exim's spool files. No bounce messages
-are ever generated.
-.next
-No retry data is maintained, and any retry rules are ignored.
-.next
-A number of Exim options are overridden: &%deliver_drop_privilege%& is forced
-true, &%max_rcpt%& in the &(smtp)& transport is forced to &"unlimited"&,
-&%remote_max_parallel%& is forced to one, and fallback hosts are ignored.
-.endlist
-
-The overall effect is that Exim makes a single synchronous attempt to deliver
-the message, failing if there is any kind of problem. Because no local
-deliveries are done and no daemon can be run, Exim does not need root
-privilege. It should be possible to run it setuid to &'exim'& instead of setuid
-to &'root'&. See section &<<SECTrunexiwitpri>>& for a general discussion about
-the advantages and disadvantages of running without root privilege.
-
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "Log files" "CHAPlog"
-.scindex IIDloggen "log" "general description"
-.cindex "log" "types of"
-Exim writes three different logs, referred to as the main log, the reject log,
-and the panic log:
-
-.ilist
-.cindex "main log"
-The main log records the arrival of each message and each delivery in a single
-line in each case. The format is as compact as possible, in an attempt to keep
-down the size of log files. Two-character flag sequences make it easy to pick
-out these lines. A number of other events are recorded in the main log. Some of
-them are optional, in which case the &%log_selector%& option controls whether
-they are included or not. A Perl script called &'eximstats'&, which does simple
-analysis of main log files, is provided in the Exim distribution (see section
-&<<SECTmailstat>>&).
-.next
-.cindex "reject log"
-The reject log records information from messages that are rejected as a result
-of a configuration option (that is, for policy reasons).
-The first line of each rejection is a copy of the line that is also written to
-the main log. Then, if the message's header has been read at the time the log
-is written, its contents are written to this log. Only the original header
-lines are available; header lines added by ACLs are not logged. You can use the
-reject log to check that your policy controls are working correctly; on a busy
-host this may be easier than scanning the main log for rejection messages. You
-can suppress the writing of the reject log by setting &%write_rejectlog%&
-false.
-.next
-.cindex "panic log"
-.cindex "system log"
-When certain serious errors occur, Exim writes entries to its panic log. If the
-error is sufficiently disastrous, Exim bombs out afterwards. Panic log entries
-are usually written to the main log as well, but can get lost amid the mass of
-other entries. The panic log should be empty under normal circumstances. It is
-therefore a good idea to check it (or to have a &'cron'& script check it)
-regularly, in order to become aware of any problems. When Exim cannot open its
-panic log, it tries as a last resort to write to the system log (syslog). This
-is opened with LOG_PID+LOG_CONS and the facility code of LOG_MAIL. The
-message itself is written at priority LOG_CRIT.
-.endlist
-
-Every log line starts with a timestamp, in the format shown in the following
-example. Note that many of the examples shown in this chapter are line-wrapped.
-In the log file, this would be all on one line:
-.code
-2001-09-16 16:09:47 SMTP connection from [127.0.0.1] closed
-  by QUIT
-.endd
-By default, the timestamps are in the local timezone. There are two
-ways of changing this:
-
-.ilist
-You can set the &%timezone%& option to a different time zone; in particular, if
-you set
-.code
-timezone = UTC
-.endd
-the timestamps will be in UTC (aka GMT).
-.next
-If you set &%log_timezone%& true, the time zone is added to the timestamp, for
-example:
-.code
-2003-04-25 11:17:07 +0100 Start queue run: pid=12762
-.endd
-.endlist
-
-.cindex "log" "process ids in"
-.cindex "pid (process id)" "in log lines"
-Exim does not include its process id in log lines by default, but you can
-request that it does so by specifying the &`pid`& log selector (see section
-&<<SECTlogselector>>&). When this is set, the process id is output, in square
-brackets, immediately after the time and date.
-
-
-
-
-.section "Where the logs are written" "SECTwhelogwri"
-.cindex "log" "destination"
-.cindex "log" "to file"
-.cindex "log" "to syslog"
-.cindex "syslog"
-The logs may be written to local files, or to syslog, or both. However, it
-should be noted that many syslog implementations use UDP as a transport, and
-are therefore unreliable in the sense that messages are not guaranteed to
-arrive at the loghost, nor is the ordering of messages necessarily maintained.
-It has also been reported that on large log files (tens of megabytes) you may
-need to tweak syslog to prevent it syncing the file with each write &-- on
-Linux this has been seen to make syslog take 90% plus of CPU time.
-
-The destination for Exim's logs is configured by setting LOG_FILE_PATH in
-&_Local/Makefile_& or by setting &%log_file_path%& in the runtime
-configuration. This latter string is expanded, so it can contain, for example,
-references to the host name:
-.code
-log_file_path = /var/log/$primary_hostname/exim_%slog
-.endd
-It is generally advisable, however, to set the string in &_Local/Makefile_&
-rather than at runtime, because then the setting is available right from the
-start of Exim's execution. Otherwise, if there's something it wants to log
-before it has read the configuration file (for example, an error in the
-configuration file) it will not use the path you want, and may not be able to
-log at all.
-
-The value of LOG_FILE_PATH or &%log_file_path%& is a colon-separated
-list, currently limited to at most two items. This is one option where the
-facility for changing a list separator may not be used. The list must always be
-colon-separated. If an item in the list is &"syslog"& then syslog is used;
-otherwise the item must either be an absolute path, containing &`%s`& at the
-point where &"main"&, &"reject"&, or &"panic"& is to be inserted, or be empty,
-implying the use of a default path.
-
-When Exim encounters an empty item in the list, it searches the list defined by
-LOG_FILE_PATH, and uses the first item it finds that is neither empty nor
-&"syslog"&. This means that an empty item in &%log_file_path%& can be used to
-mean &"use the path specified at build time"&. It no such item exists, log
-files are written in the &_log_& subdirectory of the spool directory. This is
-equivalent to the setting:
-.code
-log_file_path = $spool_directory/log/%slog
-.endd
-If you do not specify anything at build time or runtime,
-or if you unset the option at runtime (i.e. &`log_file_path = `&),
-that is where the logs are written.
-
-A log file path may also contain &`%D`& or &`%M`& if datestamped log filenames
-are in use &-- see section &<<SECTdatlogfil>>& below.
-
-Here are some examples of possible settings:
-.display
-&`LOG_FILE_PATH=syslog                    `& syslog only
-&`LOG_FILE_PATH=:syslog                   `& syslog and default path
-&`LOG_FILE_PATH=syslog : /usr/log/exim_%s `& syslog and specified path
-&`LOG_FILE_PATH=/usr/log/exim_%s          `& specified path only
-.endd
-If there are more than two paths in the list, the first is used and a panic
-error is logged.
-
-
-
-.section "Logging to local files that are periodically &""cycled""&" "SECID285"
-.cindex "log" "cycling local files"
-.cindex "cycling logs"
-.cindex "&'exicyclog'&"
-.cindex "log" "local files; writing to"
-Some operating systems provide centralized and standardized methods for cycling
-log files. For those that do not, a utility script called &'exicyclog'& is
-provided (see section &<<SECTcyclogfil>>&). This renames and compresses the
-main and reject logs each time it is called. The maximum number of old logs to
-keep can be set. It is suggested this script is run as a daily &'cron'& job.
-
-An Exim delivery process opens the main log when it first needs to write to it,
-and it keeps the file open in case subsequent entries are required &-- for
-example, if a number of different deliveries are being done for the same
-message. However, remote SMTP deliveries can take a long time, and this means
-that the file may be kept open long after it is renamed if &'exicyclog'& or
-something similar is being used to rename log files on a regular basis. To
-ensure that a switch of log files is noticed as soon as possible, Exim calls
-&[stat()]& on the main log's name before reusing an open file, and if the file
-does not exist, or its inode has changed, the old file is closed and Exim
-tries to open the main log from scratch. Thus, an old log file may remain open
-for quite some time, but no Exim processes should write to it once it has been
-renamed.
-
-
-
-.section "Datestamped log files" "SECTdatlogfil"
-.cindex "log" "datestamped files"
-Instead of cycling the main and reject log files by renaming them
-periodically, some sites like to use files whose names contain a datestamp,
-for example, &_mainlog-20031225_&. The datestamp is in the form &_yyyymmdd_& or
-&_yyyymm_&. Exim has support for this way of working. It is enabled by setting
-the &%log_file_path%& option to a path that includes &`%D`& or &`%M`& at the
-point where the datestamp is required. For example:
-.code
-log_file_path = /var/spool/exim/log/%slog-%D
-log_file_path = /var/log/exim-%s-%D.log
-log_file_path = /var/spool/exim/log/%D-%slog
-log_file_path = /var/log/exim/%s.%M
-.endd
-As before, &`%s`& is replaced by &"main"& or &"reject"&; the following are
-examples of names generated by the above examples:
-.code
-/var/spool/exim/log/mainlog-20021225
-/var/log/exim-reject-20021225.log
-/var/spool/exim/log/20021225-mainlog
-/var/log/exim/main.200212
-.endd
-When this form of log file is specified, Exim automatically switches to new
-files at midnight. It does not make any attempt to compress old logs; you
-will need to write your own script if you require this. You should not
-run &'exicyclog'& with this form of logging.
-
-The location of the panic log is also determined by &%log_file_path%&, but it
-is not datestamped, because rotation of the panic log does not make sense.
-When generating the name of the panic log, &`%D`& or &`%M`& are removed from
-the string. In addition, if it immediately follows a slash, a following
-non-alphanumeric character is removed; otherwise a preceding non-alphanumeric
-character is removed. Thus, the four examples above would give these panic
-log names:
-.code
-/var/spool/exim/log/paniclog
-/var/log/exim-panic.log
-/var/spool/exim/log/paniclog
-/var/log/exim/panic
-.endd
-
-
-.section "Logging to syslog" "SECID249"
-.cindex "log" "syslog; writing to"
-The use of syslog does not change what Exim logs or the format of its messages,
-except in one respect. If &%syslog_timestamp%& is set false, the timestamps on
-Exim's log lines are omitted when these lines are sent to syslog. Apart from
-that, the same strings are written to syslog as to log files. The syslog
-&"facility"& is set to LOG_MAIL, and the program name to &"exim"&
-by default, but you can change these by setting the &%syslog_facility%& and
-&%syslog_processname%& options, respectively. If Exim was compiled with
-SYSLOG_LOG_PID set in &_Local/Makefile_& (this is the default in
-&_src/EDITME_&), then, on systems that permit it (all except ULTRIX), the
-LOG_PID flag is set so that the &[syslog()]& call adds the pid as well as
-the time and host name to each line.
-The three log streams are mapped onto syslog priorities as follows:
-
-.ilist
-&'mainlog'& is mapped to LOG_INFO
-.next
-&'rejectlog'& is mapped to LOG_NOTICE
-.next
-&'paniclog'& is mapped to LOG_ALERT
-.endlist
-
-Many log lines are written to both &'mainlog'& and &'rejectlog'&, and some are
-written to both &'mainlog'& and &'paniclog'&, so there will be duplicates if
-these are routed by syslog to the same place. You can suppress this duplication
-by setting &%syslog_duplication%& false.
-
-Exim's log lines can sometimes be very long, and some of its &'rejectlog'&
-entries contain multiple lines when headers are included. To cope with both
-these cases, entries written to syslog are split into separate &[syslog()]&
-calls at each internal newline, and also after a maximum of
-870 data characters. (This allows for a total syslog line length of 1024, when
-additions such as timestamps are added.) If you are running a syslog
-replacement that can handle lines longer than the 1024 characters allowed by
-RFC 3164, you should set
-.code
-SYSLOG_LONG_LINES=yes
-.endd
-in &_Local/Makefile_& before building Exim. That stops Exim from splitting long
-lines, but it still splits at internal newlines in &'reject'& log entries.
-
-To make it easy to re-assemble split lines later, each component of a split
-entry starts with a string of the form [<&'n'&>/<&'m'&>] or [<&'n'&>\<&'m'&>]
-where <&'n'&> is the component number and <&'m'&> is the total number of
-components in the entry. The / delimiter is used when the line was split
-because it was too long; if it was split because of an internal newline, the \
-delimiter is used. For example, supposing the length limit to be 50 instead of
-870, the following would be the result of a typical rejection message to
-&'mainlog'& (LOG_INFO), each line in addition being preceded by the time, host
-name, and pid as added by syslog:
-.code
-[1/5] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from
-[2/5]  [127.0.0.1] (ph10): syntax error in 'From' header
-[3/5]  when scanning for sender: missing or malformed lo
-[4/5] cal part in "<>" (envelope sender is <ph10@cam.exa
-[5/5] mple>)
-.endd
-The same error might cause the following lines to be written to &"rejectlog"&
-(LOG_NOTICE):
-.code
-[1/18] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected fro
-[2/18] m [127.0.0.1] (ph10): syntax error in 'From' head
-[3/18] er when scanning for sender: missing or malformed
-[4/18]  local part in "<>" (envelope sender is <ph10@cam
-[5\18] .example>)
-[6\18] Recipients: ph10@some.domain.cam.example
-[7\18] P Received: from [127.0.0.1] (ident=ph10)
-[8\18]        by xxxxx.cam.example with smtp (Exim 4.00)
-[9\18]        id 16RdAL-0006pc-00
-[10/18]        for ph10@cam.example; Mon, 16 Sep 2002 16:
-[11\18] 09:43 +0100
-[12\18] F From: <>
-[13\18]   Subject: this is a test header
-[18\18]   X-something: this is another header
-[15/18] I Message-Id: <E16RdAL-0006pc-00@xxxxx.cam.examp
-[16\18] le>
-[17\18] B Bcc:
-[18/18]   Date: Mon, 16 Sep 2002 16:09:43 +0100
-.endd
-Log lines that are neither too long nor contain newlines are written to syslog
-without modification.
-
-If only syslog is being used, the Exim monitor is unable to provide a log tail
-display, unless syslog is routing &'mainlog'& to a file on the local host and
-the environment variable EXIMON_LOG_FILE_PATH is set to tell the monitor
-where it is.
-
-
-
-.section "Log line flags" "SECID250"
-One line is written to the main log for each message received, and for each
-successful, unsuccessful, and delayed delivery. These lines can readily be
-picked out by the distinctive two-character flags that immediately follow the
-timestamp. The flags are:
-.display
-&`<=`&     message arrival
-&`(=`&     message fakereject
-&`=>`&     normal message delivery
-&`->`&     additional address in same delivery
-&`>>`&     cutthrough message delivery
-&`*>`&     delivery suppressed by &%-N%&
-&`**`&     delivery failed; address bounced
-&`==`&     delivery deferred; temporary problem
-.endd
-
-
-.section "Logging message reception" "SECID251"
-.cindex "log" "reception line"
-The format of the single-line entry in the main log that is written for every
-message received is shown in the basic example below, which is split over
-several lines in order to fit it on the page:
-.code
-2002-10-31 08:57:53 16ZCW1-0005MB-00 <= kryten@dwarf.fict.example
-  H=mailer.fict.example [192.168.123.123] U=exim
-  P=smtp S=5678 id=<incoming message id>
-.endd
-The address immediately following &"<="& is the envelope sender address. A
-bounce message is shown with the sender address &"<>"&, and if it is locally
-generated, this is followed by an item of the form
-.code
-R=<message id>
-.endd
-which is a reference to the message that caused the bounce to be sent.
-
-.cindex "HELO"
-.cindex "EHLO"
-For messages from other hosts, the H and U fields identify the remote host and
-record the RFC 1413 identity of the user that sent the message, if one was
-received. The number given in square brackets is the IP address of the sending
-host. If there is a single, unparenthesized  host name in the H field, as
-above, it has been verified to correspond to the IP address (see the
-&%host_lookup%& option). If the name is in parentheses, it was the name quoted
-by the remote host in the SMTP HELO or EHLO command, and has not been
-verified. If verification yields a different name to that given for HELO or
-EHLO, the verified name appears first, followed by the HELO or EHLO
-name in parentheses.
-
-Misconfigured hosts (and mail forgers) sometimes put an IP address, with or
-without brackets, in the HELO or EHLO command, leading to entries in
-the log containing text like these examples:
-.code
-H=(10.21.32.43) [192.168.8.34]
-H=([10.21.32.43]) [192.168.8.34]
-.endd
-This can be confusing. Only the final address in square brackets can be relied
-on.
-
-For locally generated messages (that is, messages not received over TCP/IP),
-the H field is omitted, and the U field contains the login name of the caller
-of Exim.
-
-.cindex "authentication" "logging"
-.cindex "AUTH" "logging"
-For all messages, the P field specifies the protocol used to receive the
-message. This is the value that is stored in &$received_protocol$&. In the case
-of incoming SMTP messages, the value indicates whether or not any SMTP
-extensions (ESMTP), encryption, or authentication were used. If the SMTP
-session was encrypted, there is an additional X field that records the cipher
-suite that was used.
-
-.cindex log protocol
-The protocol is set to &"esmtpsa"& or &"esmtpa"& for messages received from
-hosts that have authenticated themselves using the SMTP AUTH command. The first
-value is used when the SMTP connection was encrypted (&"secure"&). In this case
-there is an additional item A= followed by the name of the authenticator that
-was used. If an authenticated identification was set up by the authenticator's
-&%server_set_id%& option, this is logged too, separated by a colon from the
-authenticator name.
-
-.cindex "size" "of message"
-The id field records the existing message id, if present. The size of the
-received message is given by the S field. When the message is delivered,
-headers may be removed or added, so that the size of delivered copies of the
-message may not correspond with this value (and indeed may be different to each
-other).
-
-The &%log_selector%& option can be used to request the logging of additional
-data when a message is received. See section &<<SECTlogselector>>& below.
-
-
-
-.section "Logging deliveries" "SECID252"
-.cindex "log" "delivery line"
-The format of the single-line entry in the main log that is written for every
-delivery is shown in one of the examples below, for local and remote
-deliveries, respectively. Each example has been split into multiple lines in order
-to fit it on the page:
-.code
-2002-10-31 08:59:13 16ZCW1-0005MB-00 => marv
-  <marv@hitch.fict.example> R=localuser T=local_delivery
-2002-10-31 09:00:10 16ZCW1-0005MB-00 =>
-  monk@holistic.fict.example R=dnslookup T=remote_smtp
-  H=holistic.fict.example [192.168.234.234]
-.endd
-For ordinary local deliveries, the original address is given in angle brackets
-after the final delivery address, which might be a pipe or a file. If
-intermediate address(es) exist between the original and the final address, the
-last of these is given in parentheses after the final address. The R and T
-fields record the router and transport that were used to process the address.
-
-If SMTP AUTH was used for the delivery there is an additional item A=
-followed by the name of the authenticator that was used.
-If an authenticated identification was set up by the authenticator's &%client_set_id%&
-option, this is logged too, separated by a colon from the authenticator name.
-
-If a shadow transport was run after a successful local delivery, the log line
-for the successful delivery has an item added on the end, of the form
-.display
-&`ST=<`&&'shadow transport name'&&`>`&
-.endd
-If the shadow transport did not succeed, the error message is put in
-parentheses afterwards.
-
-.cindex "asterisk" "after IP address"
-When more than one address is included in a single delivery (for example, two
-SMTP RCPT commands in one transaction) the second and subsequent addresses are
-flagged with &`->`& instead of &`=>`&. When two or more messages are delivered
-down a single SMTP connection, an asterisk follows the IP address in the log
-lines for the second and subsequent messages.
-When two or more messages are delivered down a single TLS connection, the
-DNS and some TLS-related information logged for the first message delivered
-will not be present in the log lines for the second and subsequent messages.
-TLS cipher information is still available.
-
-.cindex "delivery" "cutthrough; logging"
-.cindex "cutthrough" "logging"
-When delivery is done in cutthrough mode it is flagged with &`>>`& and the log
-line precedes the reception line, since cutthrough waits for a possible
-rejection from the destination in case it can reject the sourced item.
-
-The generation of a reply message by a filter file gets logged as a
-&"delivery"& to the addressee, preceded by &">"&.
-
-The &%log_selector%& option can be used to request the logging of additional
-data when a message is delivered. See section &<<SECTlogselector>>& below.
-
-
-.section "Discarded deliveries" "SECID253"
-.cindex "discarded messages"
-.cindex "message" "discarded"
-.cindex "delivery" "discarded; logging"
-When a message is discarded as a result of the command &"seen finish"& being
-obeyed in a filter file which generates no deliveries, a log entry of the form
-.code
-2002-12-10 00:50:49 16auJc-0001UB-00 => discarded
-  <low.club@bridge.example> R=userforward
-.endd
-is written, to record why no deliveries are logged. When a message is discarded
-because it is aliased to &":blackhole:"& the log line is like this:
-.code
-1999-03-02 09:44:33 10HmaX-0005vi-00 => :blackhole:
-  <hole@nowhere.example> R=blackhole_router
-.endd
-
-
-.section "Deferred deliveries" "SECID254"
-When a delivery is deferred, a line of the following form is logged:
-.code
-2002-12-19 16:20:23 16aiQz-0002Q5-00 == marvin@endrest.example
-  R=dnslookup T=smtp defer (146): Connection refused
-.endd
-In the case of remote deliveries, the error is the one that was given for the
-last IP address that was tried. Details of individual SMTP failures are also
-written to the log, so the above line would be preceded by something like
-.code
-2002-12-19 16:20:23 16aiQz-0002Q5-00 Failed to connect to
-  mail1.endrest.example [192.168.239.239]: Connection refused
-.endd
-When a deferred address is skipped because its retry time has not been reached,
-a message is written to the log, but this can be suppressed by setting an
-appropriate value in &%log_selector%&.
-
-
-
-.section "Delivery failures" "SECID255"
-.cindex "delivery" "failure; logging"
-If a delivery fails because an address cannot be routed, a line of the
-following form is logged:
-.code
-1995-12-19 16:20:23 0tRiQz-0002Q5-00 ** jim@trek99.example
-  <jim@trek99.example>: unknown mail domain
-.endd
-If a delivery fails at transport time, the router and transport are shown, and
-the response from the remote host is included, as in this example:
-.code
-2002-07-11 07:14:17 17SXDU-000189-00 ** ace400@pb.example
-  R=dnslookup T=remote_smtp: SMTP error from remote mailer
-  after pipelined RCPT TO:<ace400@pb.example>: host
-  pbmail3.py.example [192.168.63.111]: 553 5.3.0
-  <ace400@pb.example>...Addressee unknown
-.endd
-The word &"pipelined"& indicates that the SMTP PIPELINING extension was being
-used. See &%hosts_avoid_esmtp%& in the &(smtp)& transport for a way of
-disabling PIPELINING. The log lines for all forms of delivery failure are
-flagged with &`**`&.
-
-
-
-.section "Fake deliveries" "SECID256"
-.cindex "delivery" "fake; logging"
-If a delivery does not actually take place because the &%-N%& option has been
-used to suppress it, a normal delivery line is written to the log, except that
-&"=>"& is replaced by &"*>"&.
-
-
-
-.section "Completion" "SECID257"
-A line of the form
-.code
-2002-10-31 09:00:11 16ZCW1-0005MB-00 Completed
-.endd
-is written to the main log when a message is about to be removed from the spool
-at the end of its processing.
-
-
-
-
-.section "Summary of Fields in Log Lines" "SECID258"
-.cindex "log" "summary of fields"
-A summary of the field identifiers that are used in log lines is shown in
-the following table:
-.display
-&`A   `&        authenticator name (and optional id and sender)
-&`C   `&        SMTP confirmation on delivery
-&`    `&        command list for &"no mail in SMTP session"&
-&`CV  `&        certificate verification status
-&`D   `&        duration of &"no mail in SMTP session"&
-&`DKIM`&        domain verified in incoming message
-&`DN  `&        distinguished name from peer certificate
-&`DS  `&        DNSSEC secured lookups
-&`DT  `&        on &`=>`&, &'=='& and &'**'& lines: time taken for, or to attempt, a delivery
-&`F   `&        sender address (on delivery lines)
-&`H   `&        host name and IP address
-&`I   `&        local interface used
-&`id  `&        message id (from header) for incoming message
-&`K   `&        CHUNKING extension used
-&`L   `&        on &`<=`& and &`=>`& lines: PIPELINING extension used
-&`M8S `&        8BITMIME status for incoming message
-&`P   `&        on &`<=`& lines: protocol used
-&`    `&        on &`=>`& and &`**`& lines: return path
-&`PRDR`&        PRDR extension used
-&`PRX `&        on &`<=`& and &`=>`& lines: proxy address
-&`Q   `&        alternate queue name
-&`QT  `&        on &`=>`& lines: time spent on queue so far
-&`    `&        on &"Completed"& lines: time spent on queue
-&`R   `&        on &`<=`& lines: reference for local bounce
-&`    `&        on &`=>`&  &`>>`& &`**`& and &`==`& lines: router name
-&`RT  `&        on &`<=`& lines: time taken for reception
-&`S   `&        size of message in bytes
-&`SNI `&        server name indication from TLS client hello
-&`ST  `&        shadow transport name
-&`T   `&        on &`<=`& lines: message subject (topic)
-&`TFO `&        connection took advantage of TCP Fast Open
-&`    `&        on &`=>`& &`**`& and &`==`& lines: transport name
-&`U   `&        local user or RFC 1413 identity
-&`X   `&        TLS cipher suite
-.endd
-
-
-.section "Other log entries" "SECID259"
-Various other types of log entry are written from time to time. Most should be
-self-explanatory. Among the more common are:
-
-.ilist
-.cindex "retry" "time not reached"
-&'retry time not reached'&&~&~An address previously suffered a temporary error
-during routing or local delivery, and the time to retry has not yet arrived.
-This message is not written to an individual message log file unless it happens
-during the first delivery attempt.
-.next
-&'retry time not reached for any host'&&~&~An address previously suffered
-temporary errors during remote delivery, and the retry time has not yet arrived
-for any of the hosts to which it is routed.
-.next
-.cindex "spool directory" "file locked"
-&'spool file locked'&&~&~An attempt to deliver a message cannot proceed because
-some other Exim process is already working on the message. This can be quite
-common if queue running processes are started at frequent intervals. The
-&'exiwhat'& utility script can be used to find out what Exim processes are
-doing.
-.next
-.cindex "error" "ignored"
-&'error ignored'&&~&~There are several circumstances that give rise to this
-message:
-.olist
-Exim failed to deliver a bounce message whose age was greater than
-&%ignore_bounce_errors_after%&. The bounce was discarded.
-.next
-A filter file set up a delivery using the &"noerror"& option, and the delivery
-failed. The delivery was discarded.
-.next
-A delivery set up by a router configured with
-. ==== As this is a nested list, any displays it contains must be indented
-. ==== as otherwise they are too far to the left.
-.code
-    errors_to = <>
-.endd
-failed. The delivery was discarded.
-.endlist olist
-.next
-.cindex DKIM "log line"
-&'DKIM: d='&&~&~Verbose results of a DKIM verification attempt, if enabled for
-logging and the message has a DKIM signature header.
-.endlist ilist
-
-
-
-
-
-.section "Reducing or increasing what is logged" "SECTlogselector"
-.cindex "log" "selectors"
-By setting the &%log_selector%& global option, you can disable some of Exim's
-default logging, or you can request additional logging. The value of
-&%log_selector%& is made up of names preceded by plus or minus characters. For
-example:
-.code
-log_selector = +arguments -retry_defer
-.endd
-The list of optional log items is in the following table, with the default
-selection marked by asterisks:
-.display
-&` 8bitmime                   `&  received 8BITMIME status
-&`*acl_warn_skipped           `&  skipped &%warn%& statement in ACL
-&` address_rewrite            `&  address rewriting
-&` all_parents                `&  all parents in => lines
-&` arguments                  `&  command line arguments
-&`*connection_reject          `&  connection rejections
-&`*delay_delivery             `&  immediate delivery delayed
-&` deliver_time               `&  time taken to attempt delivery
-&` delivery_size              `&  add &`S=`&&'nnn'& to => lines
-&`*dkim                       `&  DKIM verified domain on <= lines
-&` dkim_verbose               `&  separate full DKIM verification result line, per signature
-&`*dnslist_defer              `&  defers of DNS list (aka RBL) lookups
-&` dnssec                     `&  DNSSEC secured lookups
-&`*etrn                       `&  ETRN commands
-&`*host_lookup_failed         `&  as it says
-&` ident_timeout              `&  timeout for ident connection
-&` incoming_interface         `&  local interface on <= and => lines
-&` incoming_port              `&  remote port on <= lines
-&`*lost_incoming_connection   `&  as it says (includes timeouts)
-&` millisec                   `&  millisecond timestamps and RT,QT,DT,D times
-&`*msg_id                     `&  on <= lines, Message-ID: header value
-&` msg_id_created             `&  on <= lines, Message-ID: header value when one had to be added
-&` outgoing_interface         `&  local interface on => lines
-&` outgoing_port              `&  add remote port to => lines
-&`*queue_run                  `&  start and end queue runs
-&` queue_time                 `&  time on queue for one recipient
-&` queue_time_overall         `&  time on queue for whole message
-&` pid                        `&  Exim process id
-&` pipelining                 `&  PIPELINING use, on <= and => lines
-&` proxy                      `&  proxy address on <= and => lines
-&` receive_time               `&  time taken to receive message
-&` received_recipients        `&  recipients on <= lines
-&` received_sender            `&  sender on <= lines
-&`*rejected_header            `&  header contents on reject log
-&`*retry_defer                `&  &"retry time not reached"&
-&` return_path_on_delivery    `&  put return path on => and ** lines
-&` sender_on_delivery         `&  add sender to => lines
-&`*sender_verify_fail         `&  sender verification failures
-&`*size_reject                `&  rejection because too big
-&`*skip_delivery              `&  delivery skipped in a queue run
-&`*smtp_confirmation          `&  SMTP confirmation on => lines
-&` smtp_connection            `&  incoming SMTP connections
-&` smtp_incomplete_transaction`&  incomplete SMTP transactions
-&` smtp_mailauth              `&  AUTH argument to MAIL commands
-&` smtp_no_mail               `&  session with no MAIL commands
-&` smtp_protocol_error        `&  SMTP protocol errors
-&` smtp_syntax_error          `&  SMTP syntax errors
-&` subject                    `&  contents of &'Subject:'& on <= lines
-&`*tls_certificate_verified   `&  certificate verification status
-&`*tls_cipher                 `&  TLS cipher suite on <= and => lines
-&` tls_peerdn                 `&  TLS peer DN on <= and => lines
-&` tls_sni                    `&  TLS SNI on <= lines
-&` unknown_in_list            `&  DNS lookup failed in list match
-
-&` all                        `&  all of the above
-.endd
-See also the &%slow_lookup_log%& main configuration option,
-section &<<SECID99>>&
-
-More details on each of these items follows:
-
-.ilist
-.cindex "8BITMIME"
-.cindex "log" "8BITMIME"
-&%8bitmime%&: This causes Exim to log any 8BITMIME status of received messages,
-which may help in tracking down interoperability issues with ancient MTAs
-that are not 8bit clean.  This is added to the &"<="& line, tagged with
-&`M8S=`& and a value of &`0`&, &`7`& or &`8`&, corresponding to "not given",
-&`7BIT`& and &`8BITMIME`& respectively.
-.next
-.cindex "&%warn%& ACL verb" "log when skipping"
-&%acl_warn_skipped%&: When an ACL &%warn%& statement is skipped because one of
-its conditions cannot be evaluated, a log line to this effect is written if
-this log selector is set.
-.next
-.cindex "log" "rewriting"
-.cindex "rewriting" "logging"
-&%address_rewrite%&: This applies both to global rewrites and per-transport
-rewrites, but not to rewrites in filters run as an unprivileged user (because
-such users cannot access the log).
-.next
-.cindex "log" "full parentage"
-&%all_parents%&: Normally only the original and final addresses are logged on
-delivery lines; with this selector, intermediate parents are given in
-parentheses between them.
-.next
-.cindex "log" "Exim arguments"
-.cindex "Exim arguments, logging"
-&%arguments%&: This causes Exim to write the arguments with which it was called
-to the main log, preceded by the current working directory. This is a debugging
-feature, added to make it easier to find out how certain MUAs call
-&_/usr/sbin/sendmail_&. The logging does not happen if Exim has given up root
-privilege because it was called with the &%-C%& or &%-D%& options. Arguments
-that are empty or that contain white space are quoted. Non-printing characters
-are shown as escape sequences. This facility cannot log unrecognized arguments,
-because the arguments are checked before the configuration file is read. The
-only way to log such cases is to interpose a script such as &_util/logargs.sh_&
-between the caller and Exim.
-.next
-.cindex "log" "connection rejections"
-&%connection_reject%&: A log entry is written whenever an incoming SMTP
-connection is rejected, for whatever reason.
-.next
-.cindex "log" "delayed delivery"
-.cindex "delayed delivery, logging"
-&%delay_delivery%&: A log entry is written whenever a delivery process is not
-started for an incoming message because the load is too high or too many
-messages were received on one connection. Logging does not occur if no delivery
-process is started because &%queue_only%& is set or &%-odq%& was used.
-.next
-.cindex "log" "delivery duration"
-&%deliver_time%&: For each delivery, the amount of real time it has taken to
-perform the actual delivery is logged as DT=<&'time'&>, for example, &`DT=1s`&.
-If millisecond logging is enabled, short times will be shown with greater
-precision, eg. &`DT=0.304s`&.
-.next
-.cindex "log" "message size on delivery"
-.cindex "size" "of message"
-&%delivery_size%&: For each delivery, the size of message delivered is added to
-the &"=>"& line, tagged with S=.
-.next
-.cindex log "DKIM verification"
-.cindex DKIM "verification logging"
-&%dkim%&: For message acceptance log lines, when an DKIM signature in the header
-verifies successfully a tag of DKIM is added, with one of the verified domains.
-.next
-.cindex log "DKIM verification"
-.cindex DKIM "verification logging"
-&%dkim_verbose%&: A log entry is written for each attempted DKIM verification.
-.next
-.cindex "log" "dnslist defer"
-.cindex "DNS list" "logging defer"
-.cindex "black list (DNS)"
-&%dnslist_defer%&: A log entry is written if an attempt to look up a host in a
-DNS black list suffers a temporary error.
-.next
-.cindex log dnssec
-.cindex dnssec logging
-&%dnssec%&: For message acceptance and (attempted) delivery log lines, when
-dns lookups gave secure results a tag of DS is added.
-For acceptance this covers the reverse and forward lookups for host name verification.
-It does not cover helo-name verification.
-For delivery this covers the SRV, MX, A and/or AAAA lookups.
-.next
-.cindex "log" "ETRN commands"
-.cindex "ETRN" "logging"
-&%etrn%&: Every valid ETRN command that is received is logged, before the ACL
-is run to determine whether or not it is actually accepted. An invalid ETRN
-command, or one received within a message transaction is not logged by this
-selector (see &%smtp_syntax_error%& and &%smtp_protocol_error%&).
-.next
-.cindex "log" "host lookup failure"
-&%host_lookup_failed%&: When a lookup of a host's IP addresses fails to find
-any addresses, or when a lookup of an IP address fails to find a host name, a
-log line is written. This logging does not apply to direct DNS lookups when
-routing email addresses, but it does apply to &"byname"& lookups.
-.next
-.cindex "log" "ident timeout"
-.cindex "RFC 1413" "logging timeout"
-&%ident_timeout%&: A log line is written whenever an attempt to connect to a
-client's ident port times out.
-.next
-.cindex "log" "incoming interface"
-.cindex "log" "local interface"
-.cindex "log" "local address and port"
-.cindex "TCP/IP" "logging local address and port"
-.cindex "interface" "logging"
-&%incoming_interface%&: The interface on which a message was received is added
-to the &"<="& line as an IP address in square brackets, tagged by I= and
-followed by a colon and the port number. The local interface and port are also
-added to other SMTP log lines, for example, &"SMTP connection from"&, to
-rejection lines, and (despite the name) to outgoing &"=>"& and &"->"& lines.
-The latter can be disabled by turning off the &%outgoing_interface%& option.
-.next
-.cindex log "incoming proxy address"
-.cindex proxy "logging proxy address"
-.cindex "TCP/IP" "logging proxy address"
-&%proxy%&: The internal (closest to the system running Exim) IP address
-of the proxy, tagged by PRX=, on the &"<="& line for a message accepted
-on a proxied connection
-or the &"=>"& line for a message delivered on a proxied connection.
-See &<<SECTproxyInbound>>& for more information.
-.next
-.cindex "log" "incoming remote port"
-.cindex "port" "logging remote"
-.cindex "TCP/IP" "logging incoming remote port"
-.vindex "&$sender_fullhost$&"
-.vindex "&$sender_rcvhost$&"
-&%incoming_port%&: The remote port number from which a message was received is
-added to log entries and &'Received:'& header lines, following the IP address
-in square brackets, and separated from it by a colon. This is implemented by
-changing the value that is put in the &$sender_fullhost$& and
-&$sender_rcvhost$& variables. Recording the remote port number has become more
-important with the widening use of NAT (see RFC 2505).
-.next
-.cindex "log" "dropped connection"
-&%lost_incoming_connection%&: A log line is written when an incoming SMTP
-connection is unexpectedly dropped.
-.next
-.cindex "log" "millisecond timestamps"
-.cindex millisecond logging
-.cindex timestamps "millisecond, in logs"
-&%millisec%&: Timestamps have a period and three decimal places of finer granularity
-appended to the seconds value.
-.next
-.cindex "log" "message id"
-&%msg_id%&: The value of the Message-ID: header.
-.next
-&%msg_id_created%&: The value of the Message-ID: header, when one had to be created.
-This will be either because the message is a bounce, or was submitted locally
-(submission mode) without one.
-The field identifier will have an asterix appended: &"id*="&.
-.next
-.cindex "log" "outgoing interface"
-.cindex "log" "local interface"
-.cindex "log" "local address and port"
-.cindex "TCP/IP" "logging local address and port"
-.cindex "interface" "logging"
-&%outgoing_interface%&: If &%incoming_interface%& is turned on, then the
-interface on which a message was sent is added to delivery lines as an I= tag
-followed by IP address in square brackets. You can disable this by turning
-off the &%outgoing_interface%& option.
-.next
-.cindex "log" "outgoing remote port"
-.cindex "port" "logging outgoing remote"
-.cindex "TCP/IP" "logging outgoing remote port"
-&%outgoing_port%&: The remote port number is added to delivery log lines (those
-containing => tags) following the IP address.
-The local port is also added if &%incoming_interface%& and
-&%outgoing_interface%& are both enabled.
-This option is not included in the default setting, because for most ordinary
-configurations, the remote port number is always 25 (the SMTP port), and the
-local port is a random ephemeral port.
-.next
-.cindex "log" "process ids in"
-.cindex "pid (process id)" "in log lines"
-&%pid%&: The current process id is added to every log line, in square brackets,
-immediately after the time and date.
-.next
-.cindex log pipelining
-.cindex pipelining "logging outgoing"
-&%pipelining%&: A field is added to delivery and accept
-log lines when the ESMTP PIPELINING extension was used.
-The field is a single "L".
-
-On accept lines, where PIPELINING was offered but not used by the client,
-the field has a minus appended.
-
-.cindex "pipelining" "early connection"
-If Exim is built with the SUPPORT_PIPE_CONNECT build option
-accept "L" fields have a period appended if the feature was
-offered but not used, or an asterisk appended if used.
-Delivery "L" fields have an asterisk appended if used.
-
-.next
-.cindex "log" "queue run"
-.cindex "queue runner" "logging"
-&%queue_run%&: The start and end of every queue run are logged.
-.next
-.cindex "log" "queue time"
-&%queue_time%&: The amount of time the message has been in the queue on the
-local host is logged as QT=<&'time'&> on delivery (&`=>`&) lines, for example,
-&`QT=3m45s`&. The clock starts when Exim starts to receive the message, so it
-includes reception time as well as the delivery time for the current address.
-This means that it may be longer than the difference between the arrival and
-delivery log line times, because the arrival log line is not written until the
-message has been successfully received.
-If millisecond logging is enabled, short times will be shown with greater
-precision, eg. &`QT=1.578s`&.
-.next
-&%queue_time_overall%&: The amount of time the message has been in the queue on
-the local host is logged as QT=<&'time'&> on &"Completed"& lines, for
-example, &`QT=3m45s`&. The clock starts when Exim starts to receive the
-message, so it includes reception time as well as the total delivery time.
-.next
-.cindex "log" "receive duration"
-&%receive_time%&: For each message, the amount of real time it has taken to
-perform the reception is logged as RT=<&'time'&>, for example, &`RT=1s`&.
-If millisecond logging is enabled, short times will be shown with greater
-precision, eg. &`RT=0.204s`&.
-.next
-.cindex "log" "recipients"
-&%received_recipients%&: The recipients of a message are listed in the main log
-as soon as the message is received. The list appears at the end of the log line
-that is written when a message is received, preceded by the word &"for"&. The
-addresses are listed after they have been qualified, but before any rewriting
-has taken place.
-Recipients that were discarded by an ACL for MAIL or RCPT do not appear
-in the list.
-.next
-.cindex "log" "sender reception"
-&%received_sender%&: The unrewritten original sender of a message is added to
-the end of the log line that records the message's arrival, after the word
-&"from"& (before the recipients if &%received_recipients%& is also set).
-.next
-.cindex "log" "header lines for rejection"
-&%rejected_header%&: If a message's header has been received at the time a
-rejection is written to the reject log, the complete header is added to the
-log. Header logging can be turned off individually for messages that are
-rejected by the &[local_scan()]& function (see section &<<SECTapiforloc>>&).
-.next
-.cindex "log" "retry defer"
-&%retry_defer%&: A log line is written if a delivery is deferred because a
-retry time has not yet been reached. However, this &"retry time not reached"&
-message is always omitted from individual message logs after the first delivery
-attempt.
-.next
-.cindex "log" "return path"
-&%return_path_on_delivery%&: The return path that is being transmitted with
-the message is included in delivery and bounce lines, using the tag P=.
-This is omitted if no delivery actually happens, for example, if routing fails,
-or if delivery is to &_/dev/null_& or to &`:blackhole:`&.
-.next
-.cindex "log" "sender on delivery"
-&%sender_on_delivery%&: The message's sender address is added to every delivery
-and bounce line, tagged by F= (for &"from"&).
-This is the original sender that was received with the message; it is not
-necessarily the same as the outgoing return path.
-.next
-.cindex "log" "sender verify failure"
-&%sender_verify_fail%&: If this selector is unset, the separate log line that
-gives details of a sender verification failure is not written. Log lines for
-the rejection of SMTP commands contain just &"sender verify failed"&, so some
-detail is lost.
-.next
-.cindex "log" "size rejection"
-&%size_reject%&: A log line is written whenever a message is rejected because
-it is too big.
-.next
-.cindex "log" "frozen messages; skipped"
-.cindex "frozen messages" "logging skipping"
-&%skip_delivery%&: A log line is written whenever a message is skipped during a
-queue run because it is frozen or because another process is already delivering
-it.
-.cindex "&""spool file is locked""&"
-The message that is written is &"spool file is locked"&.
-.next
-.cindex "log" "smtp confirmation"
-.cindex "SMTP" "logging confirmation"
-.cindex "LMTP" "logging confirmation"
-&%smtp_confirmation%&: The response to the final &"."& in the SMTP or LMTP dialogue for
-outgoing messages is added to delivery log lines in the form &`C=`&<&'text'&>.
-A number of MTAs (including Exim) return an identifying string in this
-response.
-.next
-.cindex "log" "SMTP connections"
-.cindex "SMTP" "logging connections"
-&%smtp_connection%&: A log line is written whenever an incoming SMTP connection is
-established or closed, unless the connection is from a host that matches
-&%hosts_connection_nolog%&. (In contrast, &%lost_incoming_connection%& applies
-only when the closure is unexpected.) This applies to connections from local
-processes that use &%-bs%& as well as to TCP/IP connections. If a connection is
-dropped in the middle of a message, a log line is always written, whether or
-not this selector is set, but otherwise nothing is written at the start and end
-of connections unless this selector is enabled.
-
-For TCP/IP connections to an Exim daemon, the current number of connections is
-included in the log message for each new connection, but note that the count is
-reset if the daemon is restarted.
-Also, because connections are closed (and the closure is logged) in
-subprocesses, the count may not include connections that have been closed but
-whose termination the daemon has not yet noticed. Thus, while it is possible to
-match up the opening and closing of connections in the log, the value of the
-logged counts may not be entirely accurate.
-.next
-.cindex "log" "SMTP transaction; incomplete"
-.cindex "SMTP" "logging incomplete transactions"
-&%smtp_incomplete_transaction%&: When a mail transaction is aborted by
-RSET, QUIT, loss of connection, or otherwise, the incident is logged,
-and the message sender plus any accepted recipients are included in the log
-line. This can provide evidence of dictionary attacks.
-.next
-.cindex "log" "non-MAIL SMTP sessions"
-.cindex "MAIL" "logging session without"
-&%smtp_no_mail%&: A line is written to the main log whenever an accepted SMTP
-connection terminates without having issued a MAIL command. This includes both
-the case when the connection is dropped, and the case when QUIT is used. It
-does not include cases where the connection is rejected right at the start (by
-an ACL, or because there are too many connections, or whatever). These cases
-already have their own log lines.
-
-The log line that is written contains the identity of the client in the usual
-way, followed by D= and a time, which records the duration of the connection.
-If the connection was authenticated, this fact is logged exactly as it is for
-an incoming message, with an A= item. If the connection was encrypted, CV=,
-DN=, and X= items may appear as they do for an incoming message, controlled by
-the same logging options.
-
-Finally, if any SMTP commands were issued during the connection, a C= item
-is added to the line, listing the commands that were used. For example,
-.code
-C=EHLO,QUIT
-.endd
-shows that the client issued QUIT straight after EHLO. If there were fewer
-than 20 commands, they are all listed. If there were more than 20 commands,
-the last 20 are listed, preceded by &"..."&. However, with the default
-setting of 10 for &%smtp_accept_max_nonmail%&, the connection will in any case
-have been aborted before 20 non-mail commands are processed.
-.next
-&%smtp_mailauth%&: A third subfield with the authenticated sender,
-colon-separated, is appended to the A= item for a message arrival or delivery
-log line, if an AUTH argument to the SMTP MAIL command (see &<<SECTauthparamail>>&)
-was accepted or used.
-.next
-.cindex "log" "SMTP protocol error"
-.cindex "SMTP" "logging protocol error"
-&%smtp_protocol_error%&: A log line is written for every SMTP protocol error
-encountered. Exim does not have perfect detection of all protocol errors
-because of transmission delays and the use of pipelining. If PIPELINING has
-been advertised to a client, an Exim server assumes that the client will use
-it, and therefore it does not count &"expected"& errors (for example, RCPT
-received after rejecting MAIL) as protocol errors.
-.next
-.cindex "SMTP" "logging syntax errors"
-.cindex "SMTP" "syntax errors; logging"
-.cindex "SMTP" "unknown command; logging"
-.cindex "log" "unknown SMTP command"
-.cindex "log" "SMTP syntax error"
-&%smtp_syntax_error%&: A log line is written for every SMTP syntax error
-encountered. An unrecognized command is treated as a syntax error. For an
-external connection, the host identity is given; for an internal connection
-using &%-bs%& the sender identification (normally the calling user) is given.
-.next
-.cindex "log" "subject"
-.cindex "subject, logging"
-&%subject%&: The subject of the message is added to the arrival log line,
-preceded by &"T="& (T for &"topic"&, since S is already used for &"size"&).
-Any MIME &"words"& in the subject are decoded. The &%print_topbitchars%& option
-specifies whether characters with values greater than 127 should be logged
-unchanged, or whether they should be rendered as escape sequences.
-.next
-.cindex "log" "certificate verification"
-.cindex log DANE
-.cindex DANE logging
-&%tls_certificate_verified%&: An extra item is added to <= and => log lines
-when TLS is in use. The item is &`CV=yes`& if the peer's certificate was
-verified
-using a CA trust anchor,
-&`CA=dane`& if using a DNS trust anchor,
-and &`CV=no`& if not.
-.next
-.cindex "log" "TLS cipher"
-.cindex "TLS" "logging cipher"
-&%tls_cipher%&: When a message is sent or received over an encrypted
-connection, the cipher suite used is added to the log line, preceded by X=.
-.next
-.cindex "log" "TLS peer DN"
-.cindex "TLS" "logging peer DN"
-&%tls_peerdn%&: When a message is sent or received over an encrypted
-connection, and a certificate is supplied by the remote host, the peer DN is
-added to the log line, preceded by DN=.
-.next
-.cindex "log" "TLS SNI"
-.cindex "TLS" "logging SNI"
-&%tls_sni%&: When a message is received over an encrypted connection, and
-the remote host provided the Server Name Indication extension, the SNI is
-added to the log line, preceded by SNI=.
-.next
-.cindex "log" "DNS failure in list"
-&%unknown_in_list%&: This setting causes a log entry to be written when the
-result of a list match is failure because a DNS lookup failed.
-.endlist
-
-
-.section "Message log" "SECID260"
-.cindex "message" "log file for"
-.cindex "log" "message log; description of"
-.cindex "&_msglog_& directory"
-.oindex "&%preserve_message_logs%&"
-In addition to the general log files, Exim writes a log file for each message
-that it handles. The names of these per-message logs are the message ids, and
-they are kept in the &_msglog_& sub-directory of the spool directory. Each
-message log contains copies of the log lines that apply to the message. This
-makes it easier to inspect the status of an individual message without having
-to search the main log. A message log is deleted when processing of the message
-is complete, unless &%preserve_message_logs%& is set, but this should be used
-only with great care because they can fill up your disk very quickly.
-
-On a heavily loaded system, it may be desirable to disable the use of
-per-message logs, in order to reduce disk I/O. This can be done by setting the
-&%message_logs%& option false.
-.ecindex IIDloggen
-
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "Exim utilities" "CHAPutils"
-.scindex IIDutils "utilities"
-A number of utility scripts and programs are supplied with Exim and are
-described in this chapter. There is also the Exim Monitor, which is covered in
-the next chapter. The utilities described here are:
-
-.itable none 0 0 3  7* left  15* left  40* left
-.irow &<<SECTfinoutwha>>&     &'exiwhat'&       &&&
-  "list what Exim processes are doing"
-.irow &<<SECTgreptheque>>&    &'exiqgrep'&      "grep the queue"
-.irow &<<SECTsumtheque>>&     &'exiqsumm'&      "summarize the queue"
-.irow &<<SECTextspeinf>>&     &'exigrep'&       "search the main log"
-.irow &<<SECTexipick>>&       &'exipick'&       "select messages on &&&
-                                                various criteria"
-.irow &<<SECTcyclogfil>>&     &'exicyclog'&     "cycle (rotate) log files"
-.irow &<<SECTmailstat>>&      &'eximstats'&     &&&
-  "extract statistics from the log"
-.irow &<<SECTcheckaccess>>&   &'exim_checkaccess'& &&&
-  "check address acceptance from given IP"
-.irow &<<SECTdbmbuild>>&      &'exim_dbmbuild'& "build a DBM file"
-.irow &<<SECTfinindret>>&     &'exinext'&       "extract retry information"
-.irow &<<SECThindatmai>>&     &'exim_dumpdb'&   "dump a hints database"
-.irow &<<SECThindatmai>>&     &'exim_tidydb'&   "clean up a hints database"
-.irow &<<SECThindatmai>>&     &'exim_fixdb'&    "patch a hints database"
-.irow &<<SECTmailboxmaint>>&  &'exim_lock'&     "lock a mailbox file"
-.endtable
-
-Another utility that might be of use to sites with many MTAs is Tom Kistner's
-&'exilog'&. It provides log visualizations across multiple Exim servers. See
-&url(https://duncanthrax.net/exilog/) for details.
-
-
-
-
-.section "Finding out what Exim processes are doing (exiwhat)" "SECTfinoutwha"
-.cindex "&'exiwhat'&"
-.cindex "process, querying"
-.cindex "SIGUSR1"
-On operating systems that can restart a system call after receiving a signal
-(most modern OS), an Exim process responds to the SIGUSR1 signal by writing
-a line describing what it is doing to the file &_exim-process.info_& in the
-Exim spool directory. The &'exiwhat'& script sends the signal to all Exim
-processes it can find, having first emptied the file. It then waits for one
-second to allow the Exim processes to react before displaying the results. In
-order to run &'exiwhat'& successfully you have to have sufficient privilege to
-send the signal to the Exim processes, so it is normally run as root.
-
-&*Warning*&: This is not an efficient process. It is intended for occasional
-use by system administrators. It is not sensible, for example, to set up a
-script that sends SIGUSR1 signals to Exim processes at short intervals.
-
-
-Unfortunately, the &'ps'& command that &'exiwhat'& uses to find Exim processes
-varies in different operating systems. Not only are different options used,
-but the format of the output is different. For this reason, there are some
-system configuration options that configure exactly how &'exiwhat'& works. If
-it doesn't seem to be working for you, check the following compile-time
-options:
-.display
-&`EXIWHAT_PS_CMD    `& the command for running &'ps'&
-&`EXIWHAT_PS_ARG    `& the argument for &'ps'&
-&`EXIWHAT_EGREP_ARG `& the argument for &'egrep'& to select from &'ps'& output
-&`EXIWHAT_KILL_ARG  `& the argument for the &'kill'& command
-.endd
-An example of typical output from &'exiwhat'& is
-.code
-164 daemon: -q1h, listening on port 25
-10483 running queue: waiting for 0tAycK-0002ij-00 (10492)
-10492 delivering 0tAycK-0002ij-00 to mail.ref.example
-  [10.19.42.42] (editor@ref.example)
-10592 handling incoming call from [192.168.243.242]
-10628 accepting a local non-SMTP message
-.endd
-The first number in the output line is the process number. The third line has
-been split here, in order to fit it on the page.
-
-
-
-.section "Selective queue listing (exiqgrep)" "SECTgreptheque"
-.cindex "&'exiqgrep'&"
-.cindex "queue" "grepping"
-This utility is a Perl script contributed by Matt Hubbard. It runs
-.code
-exim -bpu
-.endd
-or (in case &*-a*& switch is specified)
-.code
-exim -bp
-.endd
-The &*-C*& option is used to specify an alternate &_exim.conf_& which might
-contain alternate exim configuration the queue management might be using.
-
-to obtain a queue listing, and then greps the output to select messages
-that match given criteria. The following selection options are available:
-
-.vlist
-.vitem &*-f*&&~<&'regex'&>
-Match the sender address using a case-insensitive search. The field that is
-tested is enclosed in angle brackets, so you can test for bounce messages with
-.code
-exiqgrep -f '^<>$'
-.endd
-.vitem &*-r*&&~<&'regex'&>
-Match a recipient address using a case-insensitive search. The field that is
-tested is not enclosed in angle brackets.
-
-.vitem &*-s*&&~<&'regex'&>
-Match against the size field.
-
-.vitem &*-y*&&~<&'seconds'&>
-Match messages that are younger than the given time.
-
-.vitem &*-o*&&~<&'seconds'&>
-Match messages that are older than the given time.
-
-.vitem &*-z*&
-Match only frozen messages.
-
-.vitem &*-x*&
-Match only non-frozen messages.
-
-.vitem &*-G*&&~<&'queuename'&>
-Match only messages in the given queue.  Without this, the default queue is searched.
-.endlist
-
-The following options control the format of the output:
-
-.vlist
-.vitem &*-c*&
-Display only the count of matching messages.
-
-.vitem &*-l*&
-Long format &-- display the full message information as output by Exim. This is
-the default.
-
-.vitem &*-i*&
-Display message ids only.
-
-.vitem &*-b*&
-Brief format &-- one line per message.
-
-.vitem &*-R*&
-Display messages in reverse order.
-
-.vitem &*-a*&
-Include delivered recipients in queue listing.
-.endlist
-
-There is one more option, &%-h%&, which outputs a list of options.
-
-
-
-.section "Summarizing the queue (exiqsumm)" "SECTsumtheque"
-.cindex "&'exiqsumm'&"
-.cindex "queue" "summary"
-The &'exiqsumm'& utility is a Perl script which reads the output of &`exim
--bp`& and produces a summary of the messages in the queue. Thus, you use it by
-running a command such as
-.code
-exim -bp | exiqsumm
-.endd
-The output consists of one line for each domain that has messages waiting for
-it, as in the following example:
-.code
-3   2322   74m   66m  msn.com.example
-.endd
-Each line lists the number of pending deliveries for a domain, their total
-volume, and the length of time that the oldest and the newest messages have
-been waiting. Note that the number of pending deliveries is greater than the
-number of messages when messages have more than one recipient.
-
-A summary line is output at the end. By default the output is sorted on the
-domain name, but &'exiqsumm'& has the options &%-a%& and &%-c%&, which cause
-the output to be sorted by oldest message and by count of messages,
-respectively. There are also three options that split the messages for each
-domain into two or more subcounts: &%-b%& separates bounce messages, &%-f%&
-separates frozen messages, and &%-s%& separates messages according to their
-sender.
-
-The output of &'exim -bp'& contains the original addresses in the message, so
-this also applies to the output from &'exiqsumm'&. No domains from addresses
-generated by aliasing or forwarding are included (unless the &%one_time%&
-option of the &(redirect)& router has been used to convert them into &"top
-level"& addresses).
-
-
-
-
-.section "Extracting specific information from the log (exigrep)" &&&
-         "SECTextspeinf"
-.cindex "&'exigrep'&"
-.cindex "log" "extracts; grepping for"
-The &'exigrep'& utility is a Perl script that searches one or more main log
-files for entries that match a given pattern. When it finds a match, it
-extracts all the log entries for the relevant message, not just those that
-match the pattern. Thus, &'exigrep'& can extract complete log entries for a
-given message, or all mail for a given user, or for a given host, for example.
-The input files can be in Exim log format or syslog format.
-If a matching log line is not associated with a specific message, it is
-included in &'exigrep'&'s output without any additional lines. The usage is:
-.display
-&`exigrep [-t<`&&'n'&&`>] [-I] [-l] [-M] [-v] <`&&'pattern'&&`> [<`&&'log file'&&`>] ...`&
-.endd
-If no log filenames are given on the command line, the standard input is read.
-
-The &%-t%& argument specifies a number of seconds. It adds an additional
-condition for message selection. Messages that are complete are shown only if
-they spent more than <&'n'&> seconds in the queue.
-
-By default, &'exigrep'& does case-insensitive matching. The &%-I%& option
-makes it case-sensitive. This may give a performance improvement when searching
-large log files. Without &%-I%&, the Perl pattern matches use Perl's &`/i`&
-option; with &%-I%& they do not. In both cases it is possible to change the
-case sensitivity within the pattern by using &`(?i)`& or &`(?-i)`&.
-
-The &%-l%& option means &"literal"&, that is, treat all characters in the
-pattern as standing for themselves. Otherwise the pattern must be a Perl
-regular expression.
-
-The &%-v%& option inverts the matching condition. That is, a line is selected
-if it does &'not'& match the pattern.
-
-The &%-M%& options means &"related messages"&. &'exigrep'& will show messages
-that are generated as a result/response to a message that &'exigrep'& matched
-normally.
-
-Example of &%-M%&:
-user_a sends a message to user_b, which generates a bounce back to user_b. If
-&'exigrep'& is used to search for &"user_a"&, only the first message will be
-displayed.  But if &'exigrep'& is used to search for &"user_b"&, the first and
-the second (bounce) message will be displayed. Using &%-M%& with &'exigrep'&
-when searching for &"user_a"& will show both messages since the bounce is
-&"related"& to or a &"result"& of the first message that was found by the
-search term.
-
-If the location of a &'zcat'& command is known from the definition of
-ZCAT_COMMAND in &_Local/Makefile_&, &'exigrep'& automatically passes any file
-whose name ends in COMPRESS_SUFFIX through &'zcat'& as it searches it.
-If the ZCAT_COMMAND is not executable, &'exigrep'& tries to use
-autodetection of some well known compression extensions.
-
-
-.section "Selecting messages by various criteria (exipick)" "SECTexipick"
-.cindex "&'exipick'&"
-John Jetmore's &'exipick'& utility is included in the Exim distribution. It
-lists messages from the queue according to a variety of criteria. For details
-of &'exipick'&'s facilities, run &'exipick'& with
-the &%--help%& option.
-
-
-.section "Cycling log files (exicyclog)" "SECTcyclogfil"
-.cindex "log" "cycling local files"
-.cindex "cycling logs"
-.cindex "&'exicyclog'&"
-The &'exicyclog'& script can be used to cycle (rotate) &'mainlog'& and
-&'rejectlog'& files. This is not necessary if only syslog is being used, or if
-you are using log files with datestamps in their names (see section
-&<<SECTdatlogfil>>&). Some operating systems have their own standard mechanisms
-for log cycling, and these can be used instead of &'exicyclog'& if preferred.
-There are two command line options for &'exicyclog'&:
-.ilist
-&%-k%& <&'count'&> specifies the number of log files to keep, overriding the
-default that is set when Exim is built. The default default is 10.
-.next
-&%-l%& <&'path'&> specifies the log file path, in the same format as Exim's
-&%log_file_path%& option (for example, &`/var/log/exim_%slog`&), again
-overriding the script's default, which is to find the setting from Exim's
-configuration.
-.endlist
-
-Each time &'exicyclog'& is run the filenames get &"shuffled down"& by one. If
-the main log filename is &_mainlog_& (the default) then when &'exicyclog'& is
-run &_mainlog_& becomes &_mainlog.01_&, the previous &_mainlog.01_& becomes
-&_mainlog.02_& and so on, up to the limit that is set in the script or by the
-&%-k%& option. Log files whose numbers exceed the limit are discarded. Reject
-logs are handled similarly.
-
-If the limit is greater than 99, the script uses 3-digit numbers such as
-&_mainlog.001_&, &_mainlog.002_&, etc. If you change from a number less than 99
-to one that is greater, or &'vice versa'&, you will have to fix the names of
-any existing log files.
-
-If no &_mainlog_& file exists, the script does nothing. Files that &"drop off"&
-the end are deleted. All files with numbers greater than 01 are compressed,
-using a compression command which is configured by the COMPRESS_COMMAND
-setting in &_Local/Makefile_&. It is usual to run &'exicyclog'& daily from a
-root &%crontab%& entry of the form
-.code
-1 0 * * * su exim -c /usr/exim/bin/exicyclog
-.endd
-assuming you have used the name &"exim"& for the Exim user. You can run
-&'exicyclog'& as root if you wish, but there is no need.
-
-
-
-.section "Mail statistics (eximstats)" "SECTmailstat"
-.cindex "statistics"
-.cindex "&'eximstats'&"
-A Perl script called &'eximstats'& is provided for extracting statistical
-information from log files. The output is either plain text, or HTML.
-. --- 2018-09-07: LogReport's Lire appears to be dead; website is a Yahoo Japan
-. --- 404 error and everything else points to that.
-
-The &'eximstats'& script has been hacked about quite a bit over time. The
-latest version is the result of some extensive revision by Steve Campbell. A
-lot of information is given by default, but there are options for suppressing
-various parts of it. Following any options, the arguments to the script are a
-list of files, which should be main log files. For example:
-.code
-eximstats -nr /var/spool/exim/log/mainlog.01
-.endd
-By default, &'eximstats'& extracts information about the number and volume of
-messages received from or delivered to various hosts. The information is sorted
-both by message count and by volume, and the top fifty hosts in each category
-are listed on the standard output. Similar information, based on email
-addresses or domains instead of hosts can be requested by means of various
-options. For messages delivered and received locally, similar statistics are
-also produced per user.
-
-The output also includes total counts and statistics about delivery errors, and
-histograms showing the number of messages received and deliveries made in each
-hour of the day. A delivery with more than one address in its envelope (for
-example, an SMTP transaction with more than one RCPT command) is counted
-as a single delivery by &'eximstats'&.
-
-Though normally more deliveries than receipts are reported (as messages may
-have multiple recipients), it is possible for &'eximstats'& to report more
-messages received than delivered, even though the queue is empty at the start
-and end of the period in question. If an incoming message contains no valid
-recipients, no deliveries are recorded for it. A bounce message is handled as
-an entirely separate message.
-
-&'eximstats'& always outputs a grand total summary giving the volume and number
-of messages received and deliveries made, and the number of hosts involved in
-each case. It also outputs the number of messages that were delayed (that is,
-not completely delivered at the first attempt), and the number that had at
-least one address that failed.
-
-The remainder of the output is in sections that can be independently disabled
-or modified by various options. It consists of a summary of deliveries by
-transport, histograms of messages received and delivered per time interval
-(default per hour), information about the time messages spent in the queue,
-a list of relayed messages, lists of the top fifty sending hosts, local
-senders, destination hosts, and destination local users by count and by volume,
-and a list of delivery errors that occurred.
-
-The relay information lists messages that were actually relayed, that is, they
-came from a remote host and were directly delivered to some other remote host,
-without being processed (for example, for aliasing or forwarding) locally.
-
-There are quite a few options for &'eximstats'& to control exactly what it
-outputs. These are documented in the Perl script itself, and can be extracted
-by running the command &(perldoc)& on the script. For example:
-.code
-perldoc /usr/exim/bin/eximstats
-.endd
-
-.section "Checking access policy (exim_checkaccess)" "SECTcheckaccess"
-.cindex "&'exim_checkaccess'&"
-.cindex "policy control" "checking access"
-.cindex "checking access"
-The &%-bh%& command line argument allows you to run a fake SMTP session with
-debugging output, in order to check what Exim is doing when it is applying
-policy controls to incoming SMTP mail. However, not everybody is sufficiently
-familiar with the SMTP protocol to be able to make full use of &%-bh%&, and
-sometimes you just want to answer the question &"Does this address have
-access?"& without bothering with any further details.
-
-The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%&. It takes
-two arguments, an IP address and an email address:
-.code
-exim_checkaccess 10.9.8.7 A.User@a.domain.example
-.endd
-The utility runs a call to Exim with the &%-bh%& option, to test whether the
-given email address would be accepted in a RCPT command in a TCP/IP
-connection from the host with the given IP address. The output of the utility
-is either the word &"accepted"&, or the SMTP error response, for example:
-.code
-Rejected:
-550 Relay not permitted
-.endd
-When running this test, the utility uses &`<>`& as the envelope sender address
-for the MAIL command, but you can change this by providing additional
-options. These are passed directly to the Exim command. For example, to specify
-that the test is to be run with the sender address &'himself@there.example'&
-you can use:
-.code
-exim_checkaccess 10.9.8.7 A.User@a.domain.example \
-                 -f himself@there.example
-.endd
-Note that these additional Exim command line items must be given after the two
-mandatory arguments.
-
-Because the &%exim_checkaccess%& uses &%-bh%&, it does not perform callouts
-while running its checks. You can run checks that include callouts by using
-&%-bhc%&, but this is not yet available in a &"packaged"& form.
-
-
-
-.section "Making DBM files (exim_dbmbuild)" "SECTdbmbuild"
-.cindex "DBM" "building dbm files"
-.cindex "building DBM files"
-.cindex "&'exim_dbmbuild'&"
-.cindex "lower casing"
-.cindex "binary zero" "in lookup key"
-The &'exim_dbmbuild'& program reads an input file containing keys and data in
-the format used by the &(lsearch)& lookup (see section
-&<<SECTsinglekeylookups>>&). It writes a DBM file using the lower-cased alias
-names as keys and the remainder of the information as data. The lower-casing
-can be prevented by calling the program with the &%-nolc%& option.
-
-A terminating zero is included as part of the key string. This is expected by
-the &(dbm)& lookup type. However, if the option &%-nozero%& is given,
-&'exim_dbmbuild'& creates files without terminating zeroes in either the key
-strings or the data strings. The &(dbmnz)& lookup type can be used with such
-files.
-
-The program requires two arguments: the name of the input file (which can be a
-single hyphen to indicate the standard input), and the name of the output file.
-It creates the output under a temporary name, and then renames it if all went
-well.
-
-.cindex "USE_DB"
-If the native DB interface is in use (USE_DB is set in a compile-time
-configuration file &-- this is common in free versions of Unix) the two
-filenames must be different, because in this mode the Berkeley DB functions
-create a single output file using exactly the name given. For example,
-.code
-exim_dbmbuild /etc/aliases /etc/aliases.db
-.endd
-reads the system alias file and creates a DBM version of it in
-&_/etc/aliases.db_&.
-
-In systems that use the &'ndbm'& routines (mostly proprietary versions of
-Unix), two files are used, with the suffixes &_.dir_& and &_.pag_&. In this
-environment, the suffixes are added to the second argument of
-&'exim_dbmbuild'&, so it can be the same as the first. This is also the case
-when the Berkeley functions are used in compatibility mode (though this is not
-recommended), because in that case it adds a &_.db_& suffix to the filename.
-
-If a duplicate key is encountered, the program outputs a warning, and when it
-finishes, its return code is 1 rather than zero, unless the &%-noduperr%&
-option is used. By default, only the first of a set of duplicates is used &--
-this makes it compatible with &(lsearch)& lookups. There is an option
-&%-lastdup%& which causes it to use the data for the last duplicate instead.
-There is also an option &%-nowarn%&, which stops it listing duplicate keys to
-&%stderr%&. For other errors, where it doesn't actually make a new file, the
-return code is 2.
-
-
-
-
-.section "Finding individual retry times (exinext)" "SECTfinindret"
-.cindex "retry" "times"
-.cindex "&'exinext'&"
-A utility called &'exinext'& (mostly a Perl script) provides the ability to
-fish specific information out of the retry database. Given a mail domain (or a
-complete address), it looks up the hosts for that domain, and outputs any retry
-information for the hosts or for the domain. At present, the retry information
-is obtained by running &'exim_dumpdb'& (see below) and post-processing the
-output. For example:
-.code
-$ exinext piglet@milne.fict.example
-kanga.milne.example:192.168.8.1 error 146: Connection refused
-  first failed: 21-Feb-1996 14:57:34
-  last tried:   21-Feb-1996 14:57:34
-  next try at:  21-Feb-1996 15:02:34
-roo.milne.example:192.168.8.3 error 146: Connection refused
-  first failed: 20-Jan-1996 13:12:08
-  last tried:   21-Feb-1996 11:42:03
-  next try at:  21-Feb-1996 19:42:03
-  past final cutoff time
-.endd
-You can also give &'exinext'& a local part, without a domain, and it
-will give any retry information for that local part in your default domain.
-A message id can be used to obtain retry information pertaining to a specific
-message. This exists only when an attempt to deliver a message to a remote host
-suffers a message-specific error (see section &<<SECToutSMTPerr>>&).
-&'exinext'& is not particularly efficient, but then it is not expected to be
-run very often.
-
-The &'exinext'& utility calls Exim to find out information such as the location
-of the spool directory. The utility has &%-C%& and &%-D%& options, which are
-passed on to the &'exim'& commands. The first specifies an alternate Exim
-configuration file, and the second sets macros for use within the configuration
-file. These features are mainly to help in testing, but might also be useful in
-environments where more than one configuration file is in use.
-
-
-
-.section "Hints database maintenance" "SECThindatmai"
-.cindex "hints database" "maintenance"
-.cindex "maintaining Exim's hints database"
-Three utility programs are provided for maintaining the DBM files that Exim
-uses to contain its delivery hint information. Each program requires two
-arguments. The first specifies the name of Exim's spool directory, and the
-second is the name of the database it is to operate on. These are as follows:
-
-.ilist
-&'retry'&: the database of retry information
-.next
-&'wait-'&<&'transport name'&>: databases of information about messages waiting
-for remote hosts
-.next
-&'callout'&: the callout cache
-.next
-&'ratelimit'&: the data for implementing the ratelimit ACL condition
-.next
-&'misc'&: other hints data
-.endlist
-
-The &'misc'& database is used for
-
-.ilist
-Serializing ETRN runs (when &%smtp_etrn_serialize%& is set)
-.next
-Serializing delivery to a specific host (when &%serialize_hosts%& is set in an
-&(smtp)& transport)
-.next
-Limiting the concurrency of specific transports (when &%max_parallel%& is set
-in a transport)
-.endlist
-
-
-
-.section "exim_dumpdb" "SECID261"
-.cindex "&'exim_dumpdb'&"
-The entire contents of a database are written to the standard output by the
-&'exim_dumpdb'& program, which has no options or arguments other than the
-spool and database names. For example, to dump the retry database:
-.code
-exim_dumpdb /var/spool/exim retry
-.endd
-Two lines of output are produced for each entry:
-.code
-T:mail.ref.example:192.168.242.242 146 77 Connection refused
-31-Oct-1995 12:00:12 02-Nov-1995 12:21:39 02-Nov-1995 20:21:39 *
-.endd
-The first item on the first line is the key of the record. It starts with one
-of the letters R, or T, depending on whether it refers to a routing or
-transport retry. For a local delivery, the next part is the local address; for
-a remote delivery it is the name of the remote host, followed by its failing IP
-address (unless &%retry_include_ip_address%& is set false on the &(smtp)&
-transport). If the remote port is not the standard one (port 25), it is added
-to the IP address. Then there follows an error code, an additional error code,
-and a textual description of the error.
-
-The three times on the second line are the time of first failure, the time of
-the last delivery attempt, and the computed time for the next attempt. The line
-ends with an asterisk if the cutoff time for the last retry rule has been
-exceeded.
-
-Each output line from &'exim_dumpdb'& for the &'wait-xxx'& databases
-consists of a host name followed by a list of ids for messages that are or were
-waiting to be delivered to that host. If there are a very large number for any
-one host, continuation records, with a sequence number added to the host name,
-may be seen. The data in these records is often out of date, because a message
-may be routed to several alternative hosts, and Exim makes no effort to keep
-cross-references.
-
-
-
-.section "exim_tidydb" "SECID262"
-.cindex "&'exim_tidydb'&"
-The &'exim_tidydb'& utility program is used to tidy up the contents of a hints
-database. If run with no options, it removes all records that are more than 30
-days old. The age is calculated from the date and time that the record was last
-updated. Note that, in the case of the retry database, it is &'not'& the time
-since the first delivery failure. Information about a host that has been down
-for more than 30 days will remain in the database, provided that the record is
-updated sufficiently often.
-
-The cutoff date can be altered by means of the &%-t%& option, which must be
-followed by a time. For example, to remove all records older than a week from
-the retry database:
-.code
-exim_tidydb -t 7d /var/spool/exim retry
-.endd
-Both the &'wait-xxx'& and &'retry'& databases contain items that involve
-message ids. In the former these appear as data in records keyed by host &--
-they were messages that were waiting for that host &-- and in the latter they
-are the keys for retry information for messages that have suffered certain
-types of error. When &'exim_tidydb'& is run, a check is made to ensure that
-message ids in database records are those of messages that are still on the
-queue. Message ids for messages that no longer exist are removed from
-&'wait-xxx'& records, and if this leaves any records empty, they are deleted.
-For the &'retry'& database, records whose keys are non-existent message ids are
-removed. The &'exim_tidydb'& utility outputs comments on the standard output
-whenever it removes information from the database.
-
-Certain records are automatically removed by Exim when they are no longer
-needed, but others are not. For example, if all the MX hosts for a domain are
-down, a retry record is created for each one. If the primary MX host comes back
-first, its record is removed when Exim successfully delivers to it, but the
-records for the others remain because Exim has not tried to use those hosts.
-
-It is important, therefore, to run &'exim_tidydb'& periodically on all the
-hints databases. You should do this at a quiet time of day, because it requires
-a database to be locked (and therefore inaccessible to Exim) while it does its
-work. Removing records from a DBM file does not normally make the file smaller,
-but all the common DBM libraries are able to re-use the space that is released.
-After an initial phase of increasing in size, the databases normally reach a
-point at which they no longer get any bigger, as long as they are regularly
-tidied.
-
-&*Warning*&: If you never run &'exim_tidydb'&, the space used by the hints
-databases is likely to keep on increasing.
-
-
-
-
-.section "exim_fixdb" "SECID263"
-.cindex "&'exim_fixdb'&"
-The &'exim_fixdb'& program is a utility for interactively modifying databases.
-Its main use is for testing Exim, but it might also be occasionally useful for
-getting round problems in a live system. It has no options, and its interface
-is somewhat crude. On entry, it prompts for input with a right angle-bracket. A
-key of a database record can then be entered, and the data for that record is
-displayed.
-
-If &"d"& is typed at the next prompt, the entire record is deleted. For all
-except the &'retry'& database, that is the only operation that can be carried
-out. For the &'retry'& database, each field is output preceded by a number, and
-data for individual fields can be changed by typing the field number followed
-by new data, for example:
-.code
-> 4 951102:1000
-.endd
-resets the time of the next delivery attempt. Time values are given as a
-sequence of digit pairs for year, month, day, hour, and minute. Colons can be
-used as optional separators.
-
-
-
-
-.section "Mailbox maintenance (exim_lock)" "SECTmailboxmaint"
-.cindex "mailbox" "maintenance"
-.cindex "&'exim_lock'&"
-.cindex "locking mailboxes"
-The &'exim_lock'& utility locks a mailbox file using the same algorithm as
-Exim. For a discussion of locking issues, see section &<<SECTopappend>>&.
-&'Exim_lock'& can be used to prevent any modification of a mailbox by Exim or
-a user agent while investigating a problem. The utility requires the name of
-the file as its first argument. If the locking is successful, the second
-argument is run as a command (using C's &[system()]& function); if there is no
-second argument, the value of the SHELL environment variable is used; if this
-is unset or empty, &_/bin/sh_& is run. When the command finishes, the mailbox
-is unlocked and the utility ends. The following options are available:
-
-.vlist
-.vitem &%-fcntl%&
-Use &[fcntl()]& locking on the open mailbox.
-
-.vitem &%-flock%&
-Use &[flock()]& locking on the open mailbox, provided the operating system
-supports it.
-
-.vitem &%-interval%&
-This must be followed by a number, which is a number of seconds; it sets the
-interval to sleep between retries (default 3).
-
-.vitem &%-lockfile%&
-Create a lock file before opening the mailbox.
-
-.vitem &%-mbx%&
-Lock the mailbox using MBX rules.
-
-.vitem &%-q%&
-Suppress verification output.
-
-.vitem &%-retries%&
-This must be followed by a number; it sets the number of times to try to get
-the lock (default 10).
-
-.vitem &%-restore_time%&
-This option causes &%exim_lock%& to restore the modified and read times to the
-locked file before exiting. This allows you to access a locked mailbox (for
-example, to take a backup copy) without disturbing the times that the user
-subsequently sees.
-
-.vitem &%-timeout%&
-This must be followed by a number, which is a number of seconds; it sets a
-timeout to be used with a blocking &[fcntl()]& lock. If it is not set (the
-default), a non-blocking call is used.
-
-.vitem &%-v%&
-Generate verbose output.
-.endlist
-
-If none of &%-fcntl%&, &%-flock%&, &%-lockfile%& or &%-mbx%& are given, the
-default is to create a lock file and also to use &[fcntl()]& locking on the
-mailbox, which is the same as Exim's default. The use of &%-flock%& or
-&%-fcntl%& requires that the file be writeable; the use of &%-lockfile%&
-requires that the directory containing the file be writeable. Locking by lock
-file does not last forever; Exim assumes that a lock file is expired if it is
-more than 30 minutes old.
-
-The &%-mbx%& option can be used with either or both of &%-fcntl%& or
-&%-flock%&. It assumes &%-fcntl%& by default. MBX locking causes a shared lock
-to be taken out on the open mailbox, and an exclusive lock on the file
-&_/tmp/.n.m_& where &'n'& and &'m'& are the device number and inode
-number of the mailbox file. When the locking is released, if an exclusive lock
-can be obtained for the mailbox, the file in &_/tmp_& is deleted.
-
-The default output contains verification of the locking that takes place. The
-&%-v%& option causes some additional information to be given. The &%-q%& option
-suppresses all output except error messages.
-
-A command such as
-.code
-exim_lock /var/spool/mail/spqr
-.endd
-runs an interactive shell while the file is locked, whereas
-.display
-&`exim_lock -q /var/spool/mail/spqr <<End`&
-<&'some commands'&>
-&`End`&
-.endd
-runs a specific non-interactive sequence of commands while the file is locked,
-suppressing all verification output. A single command can be run by a command
-such as
-.code
-exim_lock -q /var/spool/mail/spqr \
-  "cp /var/spool/mail/spqr /some/where"
-.endd
-Note that if a command is supplied, it must be entirely contained within the
-second argument &-- hence the quotes.
-.ecindex IIDutils
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "The Exim monitor" "CHAPeximon"
-.scindex IIDeximon "Exim monitor" "description"
-.cindex "X-windows"
-.cindex "&'eximon'&"
-.cindex "Local/eximon.conf"
-.cindex "&_exim_monitor/EDITME_&"
-The Exim monitor is an application which displays in an X window information
-about the state of Exim's queue and what Exim is doing. An admin user can
-perform certain operations on messages from this GUI interface; however all
-such facilities are also available from the command line, and indeed, the
-monitor itself makes use of the command line to perform any actions requested.
-
-
-
-.section "Running the monitor" "SECID264"
-The monitor is started by running the script called &'eximon'&. This is a shell
-script that sets up a number of environment variables, and then runs the
-binary called &_eximon.bin_&. The default appearance of the monitor window can
-be changed by editing the &_Local/eximon.conf_& file created by editing
-&_exim_monitor/EDITME_&. Comments in that file describe what the various
-parameters are for.
-
-The parameters that get built into the &'eximon'& script can be overridden for
-a particular invocation by setting up environment variables of the same names,
-preceded by &`EXIMON_`&. For example, a shell command such as
-.code
-EXIMON_LOG_DEPTH=400 eximon
-.endd
-(in a Bourne-compatible shell) runs &'eximon'& with an overriding setting of
-the LOG_DEPTH parameter. If EXIMON_LOG_FILE_PATH is set in the environment, it
-overrides the Exim log file configuration. This makes it possible to have
-&'eximon'& tailing log data that is written to syslog, provided that MAIL.INFO
-syslog messages are routed to a file on the local host.
-
-X resources can be used to change the appearance of the window in the normal
-way. For example, a resource setting of the form
-.code
-Eximon*background: gray94
-.endd
-changes the colour of the background to light grey rather than white. The
-stripcharts are drawn with both the data lines and the reference lines in
-black. This means that the reference lines are not visible when on top of the
-data. However, their colour can be changed by setting a resource called
-&"highlight"& (an odd name, but that's what the Athena stripchart widget uses).
-For example, if your X server is running Unix, you could set up lighter
-reference lines in the stripcharts by obeying
-.code
-xrdb -merge <<End
-Eximon*highlight: gray
-End
-.endd
-.cindex "admin user"
-In order to see the contents of messages in the queue, and to operate on them,
-&'eximon'& must either be run as root or by an admin user.
-
-The command-line parameters of &'eximon'& are passed to &_eximon.bin_& and may
-contain X11 resource parameters interpreted by the X11 library.  In addition,
-if the first parameter starts with the string "gdb" then it is removed and the
-binary is invoked under gdb (the parameter is used as the gdb command-name, so
-versioned variants of gdb can be invoked).
-
-The monitor's window is divided into three parts. The first contains one or
-more stripcharts and two action buttons, the second contains a &"tail"& of the
-main log file, and the third is a display of the queue of messages awaiting
-delivery, with two more action buttons. The following sections describe these
-different parts of the display.
-
-
-
-
-.section "The stripcharts" "SECID265"
-.cindex "stripchart"
-The first stripchart is always a count of messages in the queue. Its name can
-be configured by setting QUEUE_STRIPCHART_NAME in the
-&_Local/eximon.conf_& file. The remaining stripcharts are defined in the
-configuration script by regular expression matches on log file entries, making
-it possible to display, for example, counts of messages delivered to certain
-hosts or using certain transports. The supplied defaults display counts of
-received and delivered messages, and of local and SMTP deliveries. The default
-period between stripchart updates is one minute; this can be adjusted by a
-parameter in the &_Local/eximon.conf_& file.
-
-The stripchart displays rescale themselves automatically as the value they are
-displaying changes. There are always 10 horizontal lines in each chart; the
-title string indicates the value of each division when it is greater than one.
-For example, &"x2"& means that each division represents a value of 2.
-
-It is also possible to have a stripchart which shows the percentage fullness of
-a particular disk partition, which is useful when local deliveries are confined
-to a single partition.
-
-.cindex "&%statvfs%& function"
-This relies on the availability of the &[statvfs()]& function or equivalent in
-the operating system. Most, but not all versions of Unix that support Exim have
-this. For this particular stripchart, the top of the chart always represents
-100%, and the scale is given as &"x10%"&. This chart is configured by setting
-SIZE_STRIPCHART and (optionally) SIZE_STRIPCHART_NAME in the
-&_Local/eximon.conf_& file.
-
-
-
-
-.section "Main action buttons" "SECID266"
-.cindex "size" "of monitor window"
-.cindex "Exim monitor" "window size"
-.cindex "window size"
-Below the stripcharts there is an action button for quitting the monitor. Next
-to this is another button marked &"Size"&. They are placed here so that
-shrinking the window to its default minimum size leaves just the queue count
-stripchart and these two buttons visible. Pressing the &"Size"& button causes
-the window to expand to its maximum size, unless it is already at the maximum,
-in which case it is reduced to its minimum.
-
-When expanding to the maximum, if the window cannot be fully seen where it
-currently is, it is moved back to where it was the last time it was at full
-size. When it is expanding from its minimum size, the old position is
-remembered, and next time it is reduced to the minimum it is moved back there.
-
-The idea is that you can keep a reduced window just showing one or two
-stripcharts at a convenient place on your screen, easily expand it to show
-the full window when required, and just as easily put it back to what it was.
-The idea is copied from what the &'twm'& window manager does for its
-&'f.fullzoom'& action. The minimum size of the window can be changed by setting
-the MIN_HEIGHT and MIN_WIDTH values in &_Local/eximon.conf_&.
-
-Normally, the monitor starts up with the window at its full size, but it can be
-built so that it starts up with the window at its smallest size, by setting
-START_SMALL=yes in &_Local/eximon.conf_&.
-
-
-
-.section "The log display" "SECID267"
-.cindex "log" "tail of; in monitor"
-The second section of the window is an area in which a display of the tail of
-the main log is maintained.
-To save space on the screen, the timestamp on each log line is shortened by
-removing the date and, if &%log_timezone%& is set, the timezone.
-The log tail is not available when the only destination for logging data is
-syslog, unless the syslog lines are routed to a local file whose name is passed
-to &'eximon'& via the EXIMON_LOG_FILE_PATH environment variable.
-
-The log sub-window has a scroll bar at its lefthand side which can be used to
-move back to look at earlier text, and the up and down arrow keys also have a
-scrolling effect. The amount of log that is kept depends on the setting of
-LOG_BUFFER in &_Local/eximon.conf_&, which specifies the amount of memory
-to use. When this is full, the earlier 50% of data is discarded &-- this is
-much more efficient than throwing it away line by line. The sub-window also has
-a horizontal scroll bar for accessing the ends of long log lines. This is the
-only means of horizontal scrolling; the right and left arrow keys are not
-available. Text can be cut from this part of the window using the mouse in the
-normal way. The size of this subwindow is controlled by parameters in the
-configuration file &_Local/eximon.conf_&.
-
-Searches of the text in the log window can be carried out by means of the ^R
-and ^S keystrokes, which default to a reverse and a forward search,
-respectively. The search covers only the text that is displayed in the window.
-It cannot go further back up the log.
-
-The point from which the search starts is indicated by a caret marker. This is
-normally at the end of the text in the window, but can be positioned explicitly
-by pointing and clicking with the left mouse button, and is moved automatically
-by a successful search. If new text arrives in the window when it is scrolled
-back, the caret remains where it is, but if the window is not scrolled back,
-the caret is moved to the end of the new text.
-
-Pressing ^R or ^S pops up a window into which the search text can be typed.
-There are buttons for selecting forward or reverse searching, for carrying out
-the search, and for cancelling. If the &"Search"& button is pressed, the search
-happens and the window remains so that further searches can be done. If the
-&"Return"& key is pressed, a single search is done and the window is closed. If
-^C is typed the search is cancelled.
-
-The searching facility is implemented using the facilities of the Athena text
-widget. By default this pops up a window containing both &"search"& and
-&"replace"& options. In order to suppress the unwanted &"replace"& portion for
-eximon, a modified version of the &%TextPop%& widget is distributed with Exim.
-However, the linkers in BSDI and HP-UX seem unable to handle an externally
-provided version of &%TextPop%& when the remaining parts of the text widget
-come from the standard libraries. The compile-time option EXIMON_TEXTPOP can be
-unset to cut out the modified &%TextPop%&, making it possible to build Eximon
-on these systems, at the expense of having unwanted items in the search popup
-window.
-
-
-
-.section "The queue display" "SECID268"
-.cindex "queue" "display in monitor"
-The bottom section of the monitor window contains a list of all messages that
-are in the queue, which includes those currently being received or delivered,
-as well as those awaiting delivery. The size of this subwindow is controlled by
-parameters in the configuration file &_Local/eximon.conf_&, and the frequency
-at which it is updated is controlled by another parameter in the same file &--
-the default is 5 minutes, since queue scans can be quite expensive. However,
-there is an &"Update"& action button just above the display which can be used
-to force an update of the queue display at any time.
-
-When a host is down for some time, a lot of pending mail can build up for it,
-and this can make it hard to deal with other messages in the queue. To help
-with this situation there is a button next to &"Update"& called &"Hide"&. If
-pressed, a dialogue box called &"Hide addresses ending with"& is put up. If you
-type anything in here and press &"Return"&, the text is added to a chain of
-such texts, and if every undelivered address in a message matches at least one
-of the texts, the message is not displayed.
-
-If there is an address that does not match any of the texts, all the addresses
-are displayed as normal. The matching happens on the ends of addresses so, for
-example, &'cam.ac.uk'& specifies all addresses in Cambridge, while
-&'xxx@foo.com.example'& specifies just one specific address. When any hiding
-has been set up, a button called &"Unhide"& is displayed. If pressed, it
-cancels all hiding. Also, to ensure that hidden messages do not get forgotten,
-a hide request is automatically cancelled after one hour.
-
-While the dialogue box is displayed, you can't press any buttons or do anything
-else to the monitor window. For this reason, if you want to cut text from the
-queue display to use in the dialogue box, you have to do the cutting before
-pressing the &"Hide"& button.
-
-The queue display contains, for each unhidden queued message, the length of
-time it has been in the queue, the size of the message, the message id, the
-message sender, and the first undelivered recipient, all on one line. If it is
-a bounce message, the sender is shown as &"<>"&. If there is more than one
-recipient to which the message has not yet been delivered, subsequent ones are
-listed on additional lines, up to a maximum configured number, following which
-an ellipsis is displayed. Recipients that have already received the message are
-not shown.
-
-.cindex "frozen messages" "display"
-If a message is frozen, an asterisk is displayed at the left-hand side.
-
-The queue display has a vertical scroll bar, and can also be scrolled by means
-of the arrow keys. Text can be cut from it using the mouse in the normal way.
-The text searching facilities, as described above for the log window, are also
-available, but the caret is always moved to the end of the text when the queue
-display is updated.
-
-
-
-.section "The queue menu" "SECID269"
-.cindex "queue" "menu in monitor"
-If the &%shift%& key is held down and the left button is clicked when the mouse
-pointer is over the text for any message, an action menu pops up, and the first
-line of the queue display for the message is highlighted. This does not affect
-any selected text.
-
-If you want to use some other event for popping up the menu, you can set the
-MENU_EVENT parameter in &_Local/eximon.conf_& to change the default, or
-set EXIMON_MENU_EVENT in the environment before starting the monitor. The
-value set in this parameter is a standard X event description. For example, to
-run eximon using &%ctrl%& rather than &%shift%& you could use
-.code
-EXIMON_MENU_EVENT='Ctrl<Btn1Down>' eximon
-.endd
-The title of the menu is the message id, and it contains entries which act as
-follows:
-
-.ilist
-&'message log'&: The contents of the message log for the message are displayed
-in a new text window.
-.next
-&'headers'&: Information from the spool file that contains the envelope
-information and headers is displayed in a new text window. See chapter
-&<<CHAPspool>>& for a description of the format of spool files.
-.next
-&'body'&: The contents of the spool file containing the body of the message are
-displayed in a new text window. There is a default limit of 20,000 bytes to the
-amount of data displayed. This can be changed by setting the BODY_MAX
-option at compile time, or the EXIMON_BODY_MAX option at runtime.
-.next
-&'deliver message'&: A call to Exim is made using the &%-M%& option to request
-delivery of the message. This causes an automatic thaw if the message is
-frozen. The &%-v%& option is also set, and the output from Exim is displayed in
-a new text window. The delivery is run in a separate process, to avoid holding
-up the monitor while the delivery proceeds.
-.next
-&'freeze message'&: A call to Exim is made using the &%-Mf%& option to request
-that the message be frozen.
-.next
-.cindex "thawing messages"
-.cindex "unfreezing messages"
-.cindex "frozen messages" "thawing"
-&'thaw message'&: A call to Exim is made using the &%-Mt%& option to request
-that the message be thawed.
-.next
-.cindex "delivery" "forcing failure"
-&'give up on msg'&: A call to Exim is made using the &%-Mg%& option to request
-that Exim gives up trying to deliver the message. A bounce message is generated
-for any remaining undelivered addresses.
-.next
-&'remove message'&: A call to Exim is made using the &%-Mrm%& option to request
-that the message be deleted from the system without generating a bounce
-message.
-.next
-&'add recipient'&: A dialog box is displayed into which a recipient address can
-be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
-is set in &_Local/eximon.conf_&, the address is qualified with that domain.
-Otherwise it must be entered as a fully qualified address. Pressing RETURN
-causes a call to Exim to be made using the &%-Mar%& option to request that an
-additional recipient be added to the message, unless the entry box is empty, in
-which case no action is taken.
-.next
-&'mark delivered'&: A dialog box is displayed into which a recipient address
-can be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
-is set in &_Local/eximon.conf_&, the address is qualified with that domain.
-Otherwise it must be entered as a fully qualified address. Pressing RETURN
-causes a call to Exim to be made using the &%-Mmd%& option to mark the given
-recipient address as already delivered, unless the entry box is empty, in which
-case no action is taken.
-.next
-&'mark all delivered'&: A call to Exim is made using the &%-Mmad%& option to
-mark all recipient addresses as already delivered.
-.next
-&'edit sender'&: A dialog box is displayed initialized with the current
-sender's address. Pressing RETURN causes a call to Exim to be made using the
-&%-Mes%& option to replace the sender address, unless the entry box is empty,
-in which case no action is taken. If you want to set an empty sender (as in
-bounce messages), you must specify it as &"<>"&. Otherwise, if the address is
-not qualified and the QUALIFY_DOMAIN parameter is set in &_Local/eximon.conf_&,
-the address is qualified with that domain.
-.endlist
-
-When a delivery is forced, a window showing the &%-v%& output is displayed. In
-other cases when a call to Exim is made, if there is any output from Exim (in
-particular, if the command fails) a window containing the command and the
-output is displayed. Otherwise, the results of the action are normally apparent
-from the log and queue displays. However, if you set ACTION_OUTPUT=yes in
-&_Local/eximon.conf_&, a window showing the Exim command is always opened, even
-if no output is generated.
-
-The queue display is automatically updated for actions such as freezing and
-thawing, unless ACTION_QUEUE_UPDATE=no has been set in
-&_Local/eximon.conf_&. In this case the &"Update"& button has to be used to
-force an update of the display after one of these actions.
-
-In any text window that is displayed as result of a menu action, the normal
-cut-and-paste facility is available, and searching can be carried out using ^R
-and ^S, as described above for the log tail window.
-.ecindex IIDeximon
-
-
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "Security considerations" "CHAPsecurity"
-.scindex IIDsecurcon "security" "discussion of"
-This chapter discusses a number of issues concerned with security, some of
-which are also covered in other parts of this manual.
-
-For reasons that this author does not understand, some people have promoted
-Exim as a &"particularly secure"& mailer. Perhaps it is because of the
-existence of this chapter in the documentation. However, the intent of the
-chapter is simply to describe the way Exim works in relation to certain
-security concerns, not to make any specific claims about the effectiveness of
-its security as compared with other MTAs.
-
-What follows is a description of the way Exim is supposed to be. Best efforts
-have been made to try to ensure that the code agrees with the theory, but an
-absence of bugs can never be guaranteed. Any that are reported will get fixed
-as soon as possible.
-
-
-.section "Building a more &""hardened""& Exim" "SECID286"
-.cindex "security" "build-time features"
-There are a number of build-time options that can be set in &_Local/Makefile_&
-to create Exim binaries that are &"harder"& to attack, in particular by a rogue
-Exim administrator who does not have the root password, or by someone who has
-penetrated the Exim (but not the root) account. These options are as follows:
-
-.ilist
-ALT_CONFIG_PREFIX can be set to a string that is required to match the
-start of any filenames used with the &%-C%& option. When it is set, these
-filenames are also not allowed to contain the sequence &"/../"&. (However, if
-the value of the &%-C%& option is identical to the value of CONFIGURE_FILE in
-&_Local/Makefile_&, Exim ignores &%-C%& and proceeds as usual.) There is no
-default setting for &%ALT_CONFIG_PREFIX%&.
-
-If the permitted configuration files are confined to a directory to
-which only root has access, this guards against someone who has broken
-into the Exim account from running a privileged Exim with an arbitrary
-configuration file, and using it to break into other accounts.
-.next
-
-If a non-trusted configuration file (i.e. not the default configuration file
-or one which is trusted by virtue of being listed in the TRUSTED_CONFIG_LIST
-file) is specified with &%-C%&, or if macros are given with &%-D%& (but see
-the next item), then root privilege is retained only if the caller of Exim is
-root. This locks out the possibility of testing a configuration using &%-C%&
-right through message reception and delivery, even if the caller is root. The
-reception works, but by that time, Exim is running as the Exim user, so when
-it re-execs to regain privilege for the delivery, the use of &%-C%& causes
-privilege to be lost. However, root can test reception and delivery using two
-separate commands.
-
-.next
-The WHITELIST_D_MACROS build option declares some macros to be safe to override
-with &%-D%& if the real uid is one of root, the Exim run-time user or the
-CONFIGURE_OWNER, if defined.  The potential impact of this option is limited by
-requiring the run-time value supplied to &%-D%& to match a regex that errs on
-the restrictive side.  Requiring build-time selection of safe macros is onerous
-but this option is intended solely as a transition mechanism to permit
-previously-working configurations to continue to work after release 4.73.
-.next
-If DISABLE_D_OPTION is defined, the use of the &%-D%& command line option
-is disabled.
-.next
-FIXED_NEVER_USERS can be set to a colon-separated list of users that are
-never to be used for any deliveries. This is like the &%never_users%& runtime
-option, but it cannot be overridden; the runtime option adds additional users
-to the list. The default setting is &"root"&; this prevents a non-root user who
-is permitted to modify the runtime file from using Exim as a way to get root.
-.endlist
-
-
-
-.section "Root privilege" "SECID270"
-.cindex "setuid"
-.cindex "root privilege"
-The Exim binary is normally setuid to root, which means that it gains root
-privilege (runs as root) when it starts execution. In some special cases (for
-example, when the daemon is not in use and there are no local deliveries), it
-may be possible to run Exim setuid to some user other than root. This is
-discussed in the next section. However, in most installations, root privilege
-is required for two things:
-
-.ilist
-To set up a socket connected to the standard SMTP port (25) when initialising
-the listening daemon. If Exim is run from &'inetd'&, this privileged action is
-not required.
-.next
-To be able to change uid and gid in order to read users' &_.forward_& files and
-perform local deliveries as the receiving user or as specified in the
-configuration.
-.endlist
-
-It is not necessary to be root to do any of the other things Exim does, such as
-receiving messages and delivering them externally over SMTP, and it is
-obviously more secure if Exim does not run as root except when necessary.
-For this reason, a user and group for Exim to use must be defined in
-&_Local/Makefile_&. These are known as &"the Exim user"& and &"the Exim
-group"&. Their values can be changed by the runtime configuration, though this
-is not recommended. Often a user called &'exim'& is used, but some sites use
-&'mail'& or another user name altogether.
-
-Exim uses &[setuid()]& whenever it gives up root privilege. This is a permanent
-abdication; the process cannot regain root afterwards. Prior to release 4.00,
-&[seteuid()]& was used in some circumstances, but this is no longer the case.
-
-After a new Exim process has interpreted its command line options, it changes
-uid and gid in the following cases:
-
-.ilist
-.oindex "&%-C%&"
-.oindex "&%-D%&"
-If the &%-C%& option is used to specify an alternate configuration file, or if
-the &%-D%& option is used to define macro values for the configuration, and the
-calling process is not running as root, the uid and gid are changed to those of
-the calling process.
-However, if DISABLE_D_OPTION is defined in &_Local/Makefile_&, the &%-D%&
-option may not be used at all.
-If WHITELIST_D_MACROS is defined in &_Local/Makefile_&, then some macro values
-can be supplied if the calling process is running as root, the Exim run-time
-user or CONFIGURE_OWNER, if defined.
-.next
-.oindex "&%-be%&"
-.oindex "&%-bf%&"
-.oindex "&%-bF%&"
-If the expansion test option (&%-be%&) or one of the filter testing options
-(&%-bf%& or &%-bF%&) are used, the uid and gid are changed to those of the
-calling process.
-.next
-If the process is not a daemon process or a queue runner process or a delivery
-process or a process for testing address routing (started with &%-bt%&), the
-uid and gid are changed to the Exim user and group. This means that Exim always
-runs under its own uid and gid when receiving messages. This also applies when
-testing address verification
-.oindex "&%-bv%&"
-.oindex "&%-bh%&"
-(the &%-bv%& option) and testing incoming message policy controls (the &%-bh%&
-option).
-.next
-For a daemon, queue runner, delivery, or address testing process, the uid
-remains as root at this stage, but the gid is changed to the Exim group.
-.endlist
-
-The processes that initially retain root privilege behave as follows:
-
-.ilist
-A daemon process changes the gid to the Exim group and the uid to the Exim
-user after setting up one or more listening sockets. The &[initgroups()]&
-function is called, so that if the Exim user is in any additional groups, they
-will be used during message reception.
-.next
-A queue runner process retains root privilege throughout its execution. Its
-job is to fork a controlled sequence of delivery processes.
-.next
-A delivery process retains root privilege throughout most of its execution,
-but any actual deliveries (that is, the transports themselves) are run in
-subprocesses which always change to a non-root uid and gid. For local
-deliveries this is typically the uid and gid of the owner of the mailbox; for
-remote deliveries, the Exim uid and gid are used. Once all the delivery
-subprocesses have been run, a delivery process changes to the Exim uid and gid
-while doing post-delivery tidying up such as updating the retry database and
-generating bounce and warning messages.
-
-While the recipient addresses in a message are being routed, the delivery
-process runs as root. However, if a user's filter file has to be processed,
-this is done in a subprocess that runs under the individual user's uid and
-gid. A system filter is run as root unless &%system_filter_user%& is set.
-.next
-A process that is testing addresses (the &%-bt%& option) runs as root so that
-the routing is done in the same environment as a message delivery.
-.endlist
-
-
-
-
-.section "Running Exim without privilege" "SECTrunexiwitpri"
-.cindex "privilege, running without"
-.cindex "unprivileged running"
-.cindex "root privilege" "running without"
-Some installations like to run Exim in an unprivileged state for more of its
-operation, for added security. Support for this mode of operation is provided
-by the global option &%deliver_drop_privilege%&. When this is set, the uid and
-gid are changed to the Exim user and group at the start of a delivery process
-(and also queue runner and address testing processes). This means that address
-routing is no longer run as root, and the deliveries themselves cannot change
-to any other uid.
-
-.cindex SIGHUP
-.cindex "daemon" "restarting"
-Leaving the binary setuid to root, but setting &%deliver_drop_privilege%& means
-that the daemon can still be started in the usual way, and it can respond
-correctly to SIGHUP because the re-invocation regains root privilege.
-
-An alternative approach is to make Exim setuid to the Exim user and also setgid
-to the Exim group. If you do this, the daemon must be started from a root
-process. (Calling Exim from a root process makes it behave in the way it does
-when it is setuid root.) However, the daemon cannot restart itself after a
-SIGHUP signal because it cannot regain privilege.
-
-It is still useful to set &%deliver_drop_privilege%& in this case, because it
-stops Exim from trying to re-invoke itself to do a delivery after a message has
-been received. Such a re-invocation is a waste of resources because it has no
-effect.
-
-If restarting the daemon is not an issue (for example, if &%mua_wrapper%& is
-set, or &'inetd'& is being used instead of a daemon), having the binary setuid
-to the Exim user seems a clean approach, but there is one complication:
-
-In this style of operation, Exim is running with the real uid and gid set to
-those of the calling process, and the effective uid/gid set to Exim's values.
-Ideally, any association with the calling process' uid/gid should be dropped,
-that is, the real uid/gid should be reset to the effective values so as to
-discard any privileges that the caller may have. While some operating systems
-have a function that permits this action for a non-root effective uid, quite a
-number of them do not. Because of this lack of standardization, Exim does not
-address this problem at this time.
-
-For this reason, the recommended approach for &"mostly unprivileged"& running
-is to keep the Exim binary setuid to root, and to set
-&%deliver_drop_privilege%&. This also has the advantage of allowing a daemon to
-be used in the most straightforward way.
-
-If you configure Exim not to run delivery processes as root, there are a
-number of restrictions on what you can do:
-
-.ilist
-You can deliver only as the Exim user/group. You should  explicitly use the
-&%user%& and &%group%& options to override routers or local transports that
-normally deliver as the recipient. This makes sure that configurations that
-work in this mode function the same way in normal mode. Any implicit or
-explicit specification of another user causes an error.
-.next
-Use of &_.forward_& files is severely restricted, such that it is usually
-not worthwhile to include them in the configuration.
-.next
-Users who wish to use &_.forward_& would have to make their home directory and
-the file itself accessible to the Exim user. Pipe and append-to-file entries,
-and their equivalents in Exim filters, cannot be used. While they could be
-enabled in the Exim user's name, that would be insecure and not very useful.
-.next
-Unless the local user mailboxes are all owned by the Exim user (possible in
-some POP3 or IMAP-only environments):
-
-.olist
-They must be owned by the Exim group and be writeable by that group. This
-implies you must set &%mode%& in the appendfile configuration, as well as the
-mode of the mailbox files themselves.
-.next
-You must set &%no_check_owner%&, since most or all of the files will not be
-owned by the Exim user.
-.next
-You must set &%file_must_exist%&, because Exim cannot set the owner correctly
-on a newly created mailbox when unprivileged. This also implies that new
-mailboxes need to be created manually.
-.endlist olist
-.endlist ilist
-
-
-These restrictions severely restrict what can be done in local deliveries.
-However, there are no restrictions on remote deliveries. If you are running a
-gateway host that does no local deliveries, setting &%deliver_drop_privilege%&
-gives more security at essentially no cost.
-
-If you are using the &%mua_wrapper%& facility (see chapter
-&<<CHAPnonqueueing>>&), &%deliver_drop_privilege%& is forced to be true.
-
-
-
-
-.section "Delivering to local files" "SECID271"
-Full details of the checks applied by &(appendfile)& before it writes to a file
-are given in chapter &<<CHAPappendfile>>&.
-
-
-
-.section "Running local commands" "SECTsecconslocalcmds"
-.cindex "security" "local commands"
-.cindex "security" "command injection attacks"
-There are a number of ways in which an administrator can configure Exim to run
-commands based upon received, untrustworthy, data. Further, in some
-configurations a user who can control a &_.forward_& file can also arrange to
-run commands. Configuration to check includes, but is not limited to:
-
-.ilist
-Use of &%use_shell%& in the pipe transport: various forms of shell command
-injection may be possible with this option present. It is dangerous and should
-be used only with considerable caution. Consider constraints which whitelist
-allowed characters in a variable which is to be used in a pipe transport that
-has &%use_shell%& enabled.
-.next
-A number of options such as &%forbid_filter_run%&, &%forbid_filter_perl%&,
-&%forbid_filter_dlfunc%& and so forth which restrict facilities available to
-&_.forward_& files in a redirect router. If Exim is running on a central mail
-hub to which ordinary users do not have shell access, but home directories are
-NFS mounted (for instance) then administrators should review the list of these
-forbid options available, and should bear in mind that the options that may
-need forbidding can change as new features are added between releases.
-.next
-The &%${run...}%& expansion item does not use a shell by default, but
-administrators can configure use of &_/bin/sh_& as part of the command.
-Such invocations should be viewed with prejudicial suspicion.
-.next
-Administrators who use embedded Perl are advised to explore how Perl's
-taint checking might apply to their usage.
-.next
-Use of &%${expand...}%& is somewhat analogous to shell's eval builtin and
-administrators are well advised to view its use with suspicion, in case (for
-instance) it allows a local-part to contain embedded Exim directives.
-.next
-Use of &%${match_local_part...}%& and friends becomes more dangerous if
-Exim was built with EXPAND_LISTMATCH_RHS defined: the second string in
-each can reference arbitrary lists and files, rather than just being a list
-of opaque strings.
-The EXPAND_LISTMATCH_RHS option was added and set false by default because of
-real-world security vulnerabilities caused by its use with untrustworthy data
-injected in, for SQL injection attacks.
-Consider the use of the &%inlisti%& expansion condition instead.
-.endlist
-
-
-
-
-.section "Trust in configuration data" "SECTsecconfdata"
-.cindex "security" "data sources"
-.cindex "security" "regular expressions"
-.cindex "regular expressions" "security"
-.cindex "PCRE" "security"
-If configuration data for Exim can come from untrustworthy sources, there
-are some issues to be aware of:
-
-.ilist
-Use of &%${expand...}%& may provide a path for shell injection attacks.
-.next
-Letting untrusted data provide a regular expression is unwise.
-.next
-Using &%${match...}%& to apply a fixed regular expression against untrusted
-data may result in pathological behaviour within PCRE.  Be aware of what
-"backtracking" means and consider options for being more strict with a regular
-expression. Avenues to explore include limiting what can match (avoiding &`.`&
-when &`[a-z0-9]`& or other character class will do), use of atomic grouping and
-possessive quantifiers or just not using regular expressions against untrusted
-data.
-.next
-It can be important to correctly use &%${quote:...}%&,
-&%${quote_local_part:...}%& and &%${quote_%&<&'lookup-type'&>&%:...}%& expansion
-items to ensure that data is correctly constructed.
-.next
-Some lookups might return multiple results, even though normal usage is only
-expected to yield one result.
-.endlist
-
-
-
-
-.section "IPv4 source routing" "SECID272"
-.cindex "source routing" "in IP packets"
-.cindex "IP source routing"
-Many operating systems suppress IP source-routed packets in the kernel, but
-some cannot be made to do this, so Exim does its own check. It logs incoming
-IPv4 source-routed TCP calls, and then drops them. Things are all different in
-IPv6. No special checking is currently done.
-
-
-
-.section "The VRFY, EXPN, and ETRN commands in SMTP" "SECID273"
-Support for these SMTP commands is disabled by default. If required, they can
-be enabled by defining suitable ACLs.
-
-
-
-
-.section "Privileged users" "SECID274"
-.cindex "trusted users"
-.cindex "admin user"
-.cindex "privileged user"
-.cindex "user" "trusted"
-.cindex "user" "admin"
-Exim recognizes two sets of users with special privileges. Trusted users are
-able to submit new messages to Exim locally, but supply their own sender
-addresses and information about a sending host. For other users submitting
-local messages, Exim sets up the sender address from the uid, and doesn't
-permit a remote host to be specified.
-
-.oindex "&%-f%&"
-However, an untrusted user is permitted to use the &%-f%& command line option
-in the special form &%-f <>%& to indicate that a delivery failure for the
-message should not cause an error report. This affects the message's envelope,
-but it does not affect the &'Sender:'& header. Untrusted users may also be
-permitted to use specific forms of address with the &%-f%& option by setting
-the &%untrusted_set_sender%& option.
-
-Trusted users are used to run processes that receive mail messages from some
-other mail domain and pass them on to Exim for delivery either locally, or over
-the Internet. Exim trusts a caller that is running as root, as the Exim user,
-as any user listed in the &%trusted_users%& configuration option, or under any
-group listed in the &%trusted_groups%& option.
-
-Admin users are permitted to do things to the messages on Exim's queue. They
-can freeze or thaw messages, cause them to be returned to their senders, remove
-them entirely, or modify them in various ways. In addition, admin users can run
-the Exim monitor and see all the information it is capable of providing, which
-includes the contents of files on the spool.
-
-.oindex "&%-M%&"
-.oindex "&%-q%&"
-By default, the use of the &%-M%& and &%-q%& options to cause Exim to attempt
-delivery of messages on its queue is restricted to admin users. This
-restriction can be relaxed by setting the &%no_prod_requires_admin%& option.
-Similarly, the use of &%-bp%& (and its variants) to list the contents of the
-queue is also restricted to admin users. This restriction can be relaxed by
-setting &%no_queue_list_requires_admin%&.
-
-Exim recognizes an admin user if the calling process is running as root or as
-the Exim user or if any of the groups associated with the calling process is
-the Exim group. It is not necessary actually to be running under the Exim
-group. However, if admin users who are not root or the Exim user are to access
-the contents of files on the spool via the Exim monitor (which runs
-unprivileged), Exim must be built to allow group read access to its spool
-files.
-
-By default, regular users are trusted to perform basic testing and
-introspection commands, as themselves.  This setting can be tightened by
-setting the &%commandline_checks_require_admin%& option.
-This affects most of the checking options,
-such as &%-be%& and anything else &%-b*%&.
-
-
-.section "Spool files" "SECID275"
-.cindex "spool directory" "files"
-Exim's spool directory and everything it contains is owned by the Exim user and
-set to the Exim group. The mode for spool files is defined in the
-&_Local/Makefile_& configuration file, and defaults to 0640. This means that
-any user who is a member of the Exim group can access these files.
-
-
-
-.section "Use of argv[0]" "SECID276"
-Exim examines the last component of &%argv[0]%&, and if it matches one of a set
-of specific strings, Exim assumes certain options. For example, calling Exim
-with the last component of &%argv[0]%& set to &"rsmtp"& is exactly equivalent
-to calling it with the option &%-bS%&. There are no security implications in
-this.
-
-
-
-.section "Use of %f formatting" "SECID277"
-The only use made of &"%f"& by Exim is in formatting load average values. These
-are actually stored in integer variables as 1000 times the load average.
-Consequently, their range is limited and so therefore is the length of the
-converted output.
-
-
-
-.section "Embedded Exim path" "SECID278"
-Exim uses its own path name, which is embedded in the code, only when it needs
-to re-exec in order to regain root privilege. Therefore, it is not root when it
-does so. If some bug allowed the path to get overwritten, it would lead to an
-arbitrary program's being run as exim, not as root.
-
-
-
-.section "Dynamic module directory" "SECTdynmoddir"
-Any dynamically loadable modules must be installed into the directory
-defined in &`LOOKUP_MODULE_DIR`& in &_Local/Makefile_& for Exim to permit
-loading it.
-
-
-.section "Use of sprintf()" "SECID279"
-.cindex "&[sprintf()]&"
-A large number of occurrences of &"sprintf"& in the code are actually calls to
-&'string_sprintf()'&, a function that returns the result in malloc'd store.
-The intermediate formatting is done into a large fixed buffer by a function
-that runs through the format string itself, and checks the length of each
-conversion before performing it, thus preventing buffer overruns.
-
-The remaining uses of &[sprintf()]& happen in controlled circumstances where
-the output buffer is known to be sufficiently long to contain the converted
-string.
-
-
-
-.section "Use of debug_printf() and log_write()" "SECID280"
-Arbitrary strings are passed to both these functions, but they do their
-formatting by calling the function &'string_vformat()'&, which runs through
-the format string itself, and checks the length of each conversion.
-
-
-
-.section "Use of strcat() and strcpy()" "SECID281"
-These are used only in cases where the output buffer is known to be large
-enough to hold the result.
-.ecindex IIDsecurcon
-
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "Format of spool files" "CHAPspool"
-.scindex IIDforspo1 "format" "spool files"
-.scindex IIDforspo2 "spool directory" "format of files"
-.scindex IIDforspo3 "spool files" "format of"
-.cindex "spool files" "editing"
-A message on Exim's queue consists of two files, whose names are the message id
-followed by -D and -H, respectively. The data portion of the message is kept in
-the -D file on its own. The message's envelope, status, and headers are all
-kept in the -H file, whose format is described in this chapter. Each of these
-two files contains the final component of its own name as its first line. This
-is insurance against disk crashes where the directory is lost but the files
-themselves are recoverable.
-
-The file formats may be changed, or new formats added, at any release.
-Spool files are not intended as an interface to other programs
-and should not be used as such.
-
-Some people are tempted into editing -D files in order to modify messages. You
-need to be extremely careful if you do this; it is not recommended and you are
-on your own if you do it. Here are some of the pitfalls:
-
-.ilist
-You must ensure that Exim does not try to deliver the message while you are
-fiddling with it. The safest way is to take out a write lock on the -D file,
-which is what Exim itself does, using &[fcntl()]&. If you update the file in
-place, the lock will be retained. If you write a new file and rename it, the
-lock will be lost at the instant of rename.
-.next
-.vindex "&$body_linecount$&"
-If you change the number of lines in the file, the value of
-&$body_linecount$&, which is stored in the -H file, will be incorrect and can
-cause incomplete transmission of messages or undeliverable messages.
-.next
-If the message is in MIME format, you must take care not to break it.
-.next
-If the message is cryptographically signed, any change will invalidate the
-signature.
-.endlist
-All in all, modifying -D files is fraught with danger.
-
-Files whose names end with -J may also be seen in the &_input_& directory (or
-its subdirectories when &%split_spool_directory%& is set). These are journal
-files, used to record addresses to which the message has been delivered during
-the course of a delivery attempt. If there are still undelivered recipients at
-the end, the -H file is updated, and the -J file is deleted. If, however, there
-is some kind of crash (for example, a power outage) before this happens, the -J
-file remains in existence. When Exim next processes the message, it notices the
--J file and uses it to update the -H file before starting the next delivery
-attempt.
-
-Files whose names end with -K or .eml may also be seen in the spool.
-These are temporaries used for DKIM or malware processing, when that is used.
-They should be tidied up by normal operations; any old ones are probably
-relics of crashes and can be removed.
-
-.section "Format of the -H file" "SECID282"
-.cindex "uid (user id)" "in spool file"
-.cindex "gid (group id)" "in spool file"
-The second line of the -H file contains the login name for the uid of the
-process that called Exim to read the message, followed by the numerical uid and
-gid. For a locally generated message, this is normally the user who sent the
-message. For a message received over TCP/IP via the daemon, it is
-normally the Exim user.
-
-The third line of the file contains the address of the message's sender as
-transmitted in the envelope, contained in angle brackets. The sender address is
-empty for bounce messages. For incoming SMTP mail, the sender address is given
-in the MAIL command. For locally generated mail, the sender address is
-created by Exim from the login name of the current user and the configured
-&%qualify_domain%&. However, this can be overridden by the &%-f%& option or a
-leading &"From&~"& line if the caller is trusted, or if the supplied address is
-&"<>"& or an address that matches &%untrusted_set_senders%&.
-
-The fourth line contains two numbers. The first is the time that the message
-was received, in the conventional Unix form &-- the number of seconds since the
-start of the epoch. The second number is a count of the number of messages
-warning of delayed delivery that have been sent to the sender.
-
-There follow a number of lines starting with a hyphen. These can appear in any
-order, and are omitted when not relevant:
-
-.vlist
-.vitem "&%-acl%&&~<&'number'&>&~<&'length'&>"
-This item is obsolete, and is not generated from Exim release 4.61 onwards;
-&%-aclc%& and &%-aclm%& are used instead. However, &%-acl%& is still
-recognized, to provide backward compatibility. In the old format, a line of
-this form is present for every ACL variable that is not empty. The number
-identifies the variable; the &%acl_c%&&*x*& variables are numbered 0&--9 and
-the &%acl_m%&&*x*& variables are numbered 10&--19. The length is the length of
-the data string for the variable. The string itself starts at the beginning of
-the next line, and is followed by a newline character. It may contain internal
-newlines.
-
-.vitem "&%-aclc%&&~<&'rest-of-name'&>&~<&'length'&>"
-A line of this form is present for every ACL connection variable that is
-defined. Note that there is a space between &%-aclc%& and the rest of the name.
-The length is the length of the data string for the variable. The string itself
-starts at the beginning of the next line, and is followed by a newline
-character. It may contain internal newlines.
-
-.vitem "&%-aclm%&&~<&'rest-of-name'&>&~<&'length'&>"
-A line of this form is present for every ACL message variable that is defined.
-Note that there is a space between &%-aclm%& and the rest of the name. The
-length is the length of the data string for the variable. The string itself
-starts at the beginning of the next line, and is followed by a newline
-character. It may contain internal newlines.
-
-.vitem "&%-active_hostname%&&~<&'hostname'&>"
-This is present if, when the message was received over SMTP, the value of
-&$smtp_active_hostname$& was different to the value of &$primary_hostname$&.
-
-.vitem &%-allow_unqualified_recipient%&
-This is present if unqualified recipient addresses are permitted in header
-lines (to stop such addresses from being qualified if rewriting occurs at
-transport time). Local messages that were input using &%-bnq%& and remote
-messages from hosts that match &%recipient_unqualified_hosts%& set this flag.
-
-.vitem &%-allow_unqualified_sender%&
-This is present if unqualified sender addresses are permitted in header lines
-(to stop such addresses from being qualified if rewriting occurs at transport
-time). Local messages that were input using &%-bnq%& and remote messages from
-hosts that match &%sender_unqualified_hosts%& set this flag.
-
-.vitem "&%-auth_id%&&~<&'text'&>"
-The id information for a message received on an authenticated SMTP connection
-&-- the value of the &$authenticated_id$& variable.
-
-.vitem "&%-auth_sender%&&~<&'address'&>"
-The address of an authenticated sender &-- the value of the
-&$authenticated_sender$& variable.
-
-.vitem "&%-body_linecount%&&~<&'number'&>"
-This records the number of lines in the body of the message, and is
-present unless &%-spool_file_wireformat%& is.
-
-.vitem "&%-body_zerocount%&&~<&'number'&>"
-This records the number of binary zero bytes in the body of the message, and is
-present if the number is greater than zero.
-
-.vitem &%-deliver_firsttime%&
-This is written when a new message is first added to the spool. When the spool
-file is updated after a deferral, it is omitted.
-
-.vitem "&%-frozen%&&~<&'time'&>"
-.cindex "frozen messages" "spool data"
-The message is frozen, and the freezing happened at <&'time'&>.
-
-.vitem "&%-helo_name%&&~<&'text'&>"
-This records the host name as specified by a remote host in a HELO or EHLO
-command.
-
-.vitem "&%-host_address%&&~<&'address'&>.<&'port'&>"
-This records the IP address of the host from which the message was received and
-the remote port number that was used. It is omitted for locally generated
-messages.
-
-.vitem "&%-host_auth%&&~<&'text'&>"
-If the message was received on an authenticated SMTP connection, this records
-the name of the authenticator &-- the value of the
-&$sender_host_authenticated$& variable.
-
-.vitem &%-host_lookup_failed%&
-This is present if an attempt to look up the sending host's name from its IP
-address failed. It corresponds to the &$host_lookup_failed$& variable.
-
-.vitem "&%-host_name%&&~<&'text'&>"
-.cindex "reverse DNS lookup"
-.cindex "DNS" "reverse lookup"
-This records the name of the remote host from which the message was received,
-if the host name was looked up from the IP address when the message was being
-received. It is not present if no reverse lookup was done.
-
-.vitem "&%-ident%&&~<&'text'&>"
-For locally submitted messages, this records the login of the originating user,
-unless it was a trusted user and the &%-oMt%& option was used to specify an
-ident value. For messages received over TCP/IP, this records the ident string
-supplied by the remote host, if any.
-
-.vitem "&%-interface_address%&&~<&'address'&>.<&'port'&>"
-This records the IP address of the local interface and the port number through
-which a message was received from a remote host. It is omitted for locally
-generated messages.
-
-.vitem &%-local%&
-The message is from a local sender.
-
-.vitem &%-localerror%&
-The message is a locally-generated bounce message.
-
-.vitem "&%-local_scan%&&~<&'string'&>"
-This records the data string that was returned by the &[local_scan()]& function
-when the message was received &-- the value of the &$local_scan_data$&
-variable. It is omitted if no data was returned.
-
-.vitem &%-manual_thaw%&
-The message was frozen but has been thawed manually, that is, by an explicit
-Exim command rather than via the auto-thaw process.
-
-.vitem &%-N%&
-A testing delivery process was started using the &%-N%& option to suppress any
-actual deliveries, but delivery was deferred. At any further delivery attempts,
-&%-N%& is assumed.
-
-.vitem &%-received_protocol%&
-This records the value of the &$received_protocol$& variable, which contains
-the name of the protocol by which the message was received.
-
-.vitem &%-sender_set_untrusted%&
-The envelope sender of this message was set by an untrusted local caller (used
-to ensure that the caller is displayed in queue listings).
-
-.vitem "&%-spam_score_int%&&~<&'number'&>"
-If a message was scanned by SpamAssassin, this is present. It records the value
-of &$spam_score_int$&.
-
-.vitem &%-spool_file_wireformat%&
-The -D file for this message is in wire-format (for ESMTP CHUNKING)
-rather than Unix-format.
-The line-ending is CRLF rather than newline.
-There is still, however, no leading-dot-stuffing.
-
-.vitem &%-tls_certificate_verified%&
-A TLS certificate was received from the client that sent this message, and the
-certificate was verified by the server.
-
-.vitem "&%-tls_cipher%&&~<&'cipher name'&>"
-When the message was received over an encrypted connection, this records the
-name of the cipher suite that was used.
-
-.vitem "&%-tls_peerdn%&&~<&'peer DN'&>"
-When the message was received over an encrypted connection, and a certificate
-was received from the client, this records the Distinguished Name from that
-certificate.
-.endlist
-
-Any of the above may have an extra hyphen prepended, to indicate the the
-corresponding data is untrusted.
-
-Following the options there is a list of those addresses to which the message
-is not to be delivered. This set of addresses is initialized from the command
-line when the &%-t%& option is used and &%extract_addresses_remove_arguments%&
-is set; otherwise it starts out empty. Whenever a successful delivery is made,
-the address is added to this set. The addresses are kept internally as a
-balanced binary tree, and it is a representation of that tree which is written
-to the spool file. If an address is expanded via an alias or forward file, the
-original address is added to the tree when deliveries to all its child
-addresses are complete.
-
-If the tree is empty, there is a single line in the spool file containing just
-the text &"XX"&. Otherwise, each line consists of two letters, which are either
-Y or N, followed by an address. The address is the value for the node of the
-tree, and the letters indicate whether the node has a left branch and/or a
-right branch attached to it, respectively. If branches exist, they immediately
-follow. Here is an example of a three-node tree:
-.code
-YY darcy@austen.fict.example
-NN alice@wonderland.fict.example
-NN editor@thesaurus.ref.example
-.endd
-After the non-recipients tree, there is a list of the message's recipients.
-This is a simple list, preceded by a count. It includes all the original
-recipients of the message, including those to whom the message has already been
-delivered. In the simplest case, the list contains one address per line. For
-example:
-.code
-4
-editor@thesaurus.ref.example
-darcy@austen.fict.example
-rdo@foundation
-alice@wonderland.fict.example
-.endd
-However, when a child address has been added to the top-level addresses as a
-result of the use of the &%one_time%& option on a &(redirect)& router, each
-line is of the following form:
-.display
-<&'top-level address'&> <&'errors_to address'&> &&&
-  <&'length'&>,<&'parent number'&>#<&'flag bits'&>
-.endd
-The 01 flag bit indicates the presence of the three other fields that follow
-the top-level address. Other bits may be used in future to support additional
-fields. The <&'parent number'&> is the offset in the recipients list of the
-original parent of the &"one time"& address. The first two fields are the
-envelope sender that is associated with this address and its length. If the
-length is zero, there is no special envelope sender (there are then two space
-characters in the line). A non-empty field can arise from a &(redirect)& router
-that has an &%errors_to%& setting.
-
-
-A blank line separates the envelope and status information from the headers
-which follow. A header may occupy several lines of the file, and to save effort
-when reading it in, each header is preceded by a number and an identifying
-character. The number is the number of characters in the header, including any
-embedded newlines and the terminating newline. The character is one of the
-following:
-
-.table2 50pt
-.row <&'blank'&>         "header in which Exim has no special interest"
-.row &`B`&               "&'Bcc:'& header"
-.row &`C`&               "&'Cc:'& header"
-.row &`F`&               "&'From:'& header"
-.row &`I`&               "&'Message-id:'& header"
-.row &`P`&               "&'Received:'& header &-- P for &""postmark""&"
-.row &`R`&               "&'Reply-To:'& header"
-.row &`S`&               "&'Sender:'& header"
-.row &`T`&               "&'To:'& header"
-.row &`*`&               "replaced or deleted header"
-.endtable
-
-Deleted or replaced (rewritten) headers remain in the spool file for debugging
-purposes. They are not transmitted when the message is delivered. Here is a
-typical set of headers:
-.code
-111P Received: by hobbit.fict.example with local (Exim 4.00)
-id 14y9EI-00026G-00; Fri, 11 May 2001 10:28:59 +0100
-049  Message-Id: <E14y9EI-00026G-00@hobbit.fict.example>
-038* X-rewrote-sender: bb@hobbit.fict.example
-042* From: Bilbo Baggins <bb@hobbit.fict.example>
-049F From: Bilbo Baggins <B.Baggins@hobbit.fict.example>
-099* To: alice@wonderland.fict.example, rdo@foundation,
-darcy@austen.fict.example, editor@thesaurus.ref.example
-104T To: alice@wonderland.fict.example, rdo@foundation.example,
-darcy@austen.fict.example, editor@thesaurus.ref.example
-038  Date: Fri, 11 May 2001 10:28:59 +0100
-.endd
-The asterisked headers indicate that the envelope sender, &'From:'& header, and
-&'To:'& header have been rewritten, the last one because routing expanded the
-unqualified domain &'foundation'&.
-.ecindex IIDforspo1
-.ecindex IIDforspo2
-.ecindex IIDforspo3
-
-.section "Format of the -D file" "SECID282a"
-The data file is traditionally in Unix-standard format: lines are ended with
-an ASCII newline character.
-However, when the &%spool_wireformat%& main option is used some -D files
-can have an alternate format.
-This is flagged by a &%-spool_file_wireformat%& line in the corresponding -H file.
-The -D file lines (not including the first name-component line) are
-suitable for direct copying to the wire when transmitting using the
-ESMTP CHUNKING option, meaning lower processing overhead.
-Lines are terminated with an ASCII CRLF pair.
-There is no dot-stuffing (and no dot-termination).
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "DKIM, SPF and DMARC" "CHAPdkim" &&&
-         "DKIM, SPF and DMARC Support"
-
-.section "DKIM (DomainKeys Identified Mail)" SECDKIM
-.cindex "DKIM"
-
-DKIM is a mechanism by which messages sent by some entity can be provably
-linked to a domain which that entity controls.  It permits reputation to
-be tracked on a per-domain basis, rather than merely upon source IP address.
-DKIM is documented in RFC 6376.
-
-As DKIM relies on the message being unchanged in transit, messages handled
-by a mailing-list (which traditionally adds to the message) will not match
-any original DKIM signature.
-
-DKIM support is compiled into Exim by default if TLS support is present.
-It can be disabled by setting DISABLE_DKIM=yes in &_Local/Makefile_&.
-
-Exim's DKIM implementation allows for
-.olist
-Signing outgoing messages: This function is implemented in the SMTP transport.
-It can co-exist with all other Exim features
-(including transport filters)
-except cutthrough delivery.
-.next
-Verifying signatures in incoming messages: This is implemented by an additional
-ACL (acl_smtp_dkim), which can be called several times per message, with
-different signature contexts.
-.endlist
-
-In typical Exim style, the verification implementation does not include any
-default "policy". Instead it enables you to build your own policy using
-Exim's standard controls.
-
-Please note that verification of DKIM signatures in incoming mail is turned
-on by default for logging (in the <= line) purposes.
-
-Additional log detail can be enabled using the &%dkim_verbose%& log_selector.
-When set, for each signature in incoming email,
-exim will log a line displaying the most important signature details, and the
-signature status. Here is an example (with line-breaks added for clarity):
-.code
-2009-09-09 10:22:28 1MlIRf-0003LU-U3 DKIM:
-    d=facebookmail.com s=q1-2009b
-    c=relaxed/relaxed a=rsa-sha1
-    i=@facebookmail.com t=1252484542 [verification succeeded]
-.endd
-
-You might want to turn off DKIM verification processing entirely for internal
-or relay mail sources. To do that, set the &%dkim_disable_verify%& ACL
-control modifier. This should typically be done in the RCPT ACL, at points
-where you accept mail from relay sources (internal hosts or authenticated
-senders).
-
-
-.section "Signing outgoing messages" "SECDKIMSIGN"
-.cindex "DKIM" "signing"
-
-For signing to be usable you must have published a DKIM record in DNS.
-Note that RFC 8301 (which does not cover EC keys) says:
-.code
-rsa-sha1 MUST NOT be used for signing or verifying.
-
-Signers MUST use RSA keys of at least 1024 bits for all keys.
-Signers SHOULD use RSA keys of at least 2048 bits.
-.endd
-
-Note also that the key content (the 'p=' field)
-in the DNS record is different between RSA and EC keys;
-for the former it is the base64 of the ASN.1 for the RSA public key
-(equivalent to the private-key .pem with the header/trailer stripped)
-but for EC keys it is the base64 of the pure key; no ASN.1 wrapping.
-
-Signing is enabled by setting private options on the SMTP transport.
-These options take (expandable) strings as arguments.
-
-.option dkim_domain smtp string list&!! unset
-The domain(s) you want to sign with.
-After expansion, this can be a list.
-Each element in turn,
-lowercased,
-is put into the &%$dkim_domain%& expansion variable
-while expanding the remaining signing options.
-If it is empty after expansion, DKIM signing is not done,
-and no error will result even if &%dkim_strict%& is set.
-
-.option dkim_selector smtp string list&!! unset
-This sets the key selector string.
-After expansion, which can use &$dkim_domain$&, this can be a list.
-Each element in turn is put in the expansion
-variable &%$dkim_selector%& which may be used in the &%dkim_private_key%&
-option along with &%$dkim_domain%&.
-If the option is empty after expansion, DKIM signing is not done for this domain,
-and no error will result even if &%dkim_strict%& is set.
-
-.option dkim_private_key smtp string&!! unset
-This sets the private key to use.
-You can use the &%$dkim_domain%& and
-&%$dkim_selector%& expansion variables to determine the private key to use.
-The result can either
-.ilist
-be a valid RSA private key in ASCII armor (.pem file), including line breaks
-.next
-with GnuTLS 3.6.0 or OpenSSL 1.1.1 or later,
-be a valid Ed25519 private key (same format as above)
-.next
-start with a slash, in which case it is treated as a file that contains
-the private key
-.next
-be "0", "false" or the empty string, in which case the message will not
-be signed. This case will not result in an error, even if &%dkim_strict%&
-is set.
-.endlist
-
-To generate keys under OpenSSL:
-.code
-openssl genrsa -out dkim_rsa.private 2048
-openssl rsa -in dkim_rsa.private -out /dev/stdout -pubout -outform PEM
-.endd
-The result file from the first command should be retained, and
-this option set to use it.
-Take the base-64 lines from the output of the second command, concatenated,
-for the DNS TXT record.
-See section 3.6 of RFC6376 for the record specification.
-
-Under GnuTLS:
-.code
-certtool --generate-privkey --rsa --bits=2048 --password='' -8 --outfile=dkim_rsa.private
-certtool --load-privkey=dkim_rsa.private --pubkey-info
-.endd
-
-Note that RFC 8301 says:
-.code
-Signers MUST use RSA keys of at least 1024 bits for all keys.
-Signers SHOULD use RSA keys of at least 2048 bits.
-.endd
-
-EC keys for DKIM are defined by RFC 8463.
-They are considerably smaller than RSA keys for equivalent protection.
-As they are a recent development, users should consider dual-signing
-(by setting a list of selectors, and an expansion for this option)
-for some transition period.
-The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
-for EC keys.
-
-OpenSSL 1.1.1 and GnuTLS 3.6.0 can create Ed25519 private keys:
-.code
-openssl genpkey -algorithm ed25519 -out dkim_ed25519.private
-certtool --generate-privkey --key-type=ed25519 --outfile=dkim_ed25519.private
-.endd
-
-To produce the required public key value for a DNS record:
-.code
-openssl pkey -outform DER -pubout -in dkim_ed25519.private | tail -c +13 | base64
-certtool --load_privkey=dkim_ed25519.private --pubkey_info --outder | tail -c +13 | base64
-.endd
-
-Exim also supports an alternate format
-of Ed25519 keys in DNS which was a candidate during development
-of the standard, but not adopted.
-A future release will probably drop that support.
-
-.option dkim_hash smtp string&!! sha256
-Can be set to any one of the supported hash methods, which are:
-.ilist
-&`sha1`& &-- should not be used, is old and insecure
-.next
-&`sha256`& &-- the default
-.next
-&`sha512`& &-- possibly more secure but less well supported
-.endlist
-
-Note that RFC 8301 says:
-.code
-rsa-sha1 MUST NOT be used for signing or verifying.
-.endd
-
-.option dkim_identity smtp string&!! unset
-If set after expansion, the value is used to set an "i=" tag in
-the signing header.  The DKIM standards restrict the permissible
-syntax of this optional tag to a mail address, with possibly-empty
-local part, an @, and a domain identical to or subdomain of the "d="
-tag value.  Note that Exim does not check the value.
-
-.option dkim_canon smtp string&!! unset
-This option sets the canonicalization method used when signing a message.
-The DKIM RFC currently supports two methods: "simple" and "relaxed".
-The option defaults to "relaxed" when unset. Note: the current implementation
-only supports signing with the same canonicalization method for both headers and body.
-
-.option dkim_strict smtp string&!! unset
-This  option  defines  how  Exim  behaves  when  signing a message that
-should be signed fails for some reason.  When the expansion evaluates to
-either &"1"& or &"true"&, Exim will defer. Otherwise Exim will send the message
-unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion
-variables here.
-
-.option dkim_sign_headers smtp string&!! "see below"
-If set, this option must expand to a colon-separated
-list of header names.
-Headers with these names, or the absence or such a header, will be included
-in the message signature.
-When unspecified, the header names listed in RFC4871 will be used,
-whether or not each header is present in the message.
-The default list is available for the expansion in the macro
-&"_DKIM_SIGN_HEADERS"&
-.new
-and an oversigning variant is in &"_DKIM_OVERSIGN_HEADERS"&.
-.wen
-
-If a name is repeated, multiple headers by that name (or the absence thereof)
-will be signed.  The textually later headers in the headers part of the
-message are signed first, if there are multiples.
-
-A name can be prefixed with either an &"="& or a &"+"& character.
-If an &"="& prefix is used, all headers that are present with this name
-will be signed.
-If a &"+"& prefix if used, all headers that are present with this name
-will be signed, and one signature added for a missing header with the
-name will be appended.
-
-.option dkim_timestamps smtp integer&!! unset
-This option controls the inclusion of timestamp information in the signature.
-If not set, no such information will be included.
-Otherwise, must be an unsigned number giving an offset in seconds from the current time
-for the expiry tag
-(eg. 1209600 for two weeks);
-both creation (t=) and expiry (x=) tags will be included.
-
-RFC 6376 lists these tags as RECOMMENDED.
-
-
-.section "Verifying DKIM signatures in incoming mail" "SECDKIMVFY"
-.cindex "DKIM" "verification"
-
-Verification of DKIM signatures in SMTP incoming email is done for all
-messages for which an ACL control &%dkim_disable_verify%& has not been set.
-.cindex DKIM "selecting signature algorithms"
-Individual classes of signature algorithm can be ignored by changing
-the main options &%dkim_verify_hashes%& or &%dkim_verify_keytypes%&.
-The &%dkim_verify_minimal%& option can be set to cease verification
-processing for a message once the first passing signature is found.
-
-.cindex authentication "expansion item"
-Performing verification sets up information used by the
-&%authresults%& expansion item.
-
-For most purposes the default option settings suffice and the remainder
-of this section can be ignored.
-
-The results of verification are made available to the
-&%acl_smtp_dkim%& ACL, which can examine and modify them.
-A missing ACL definition defaults to accept.
-By default, the ACL is called once for each
-syntactically(!) correct signature in the incoming message.
-If any ACL call does not accept, the message is not accepted.
-If a cutthrough delivery was in progress for the message, that is
-summarily dropped (having wasted the transmission effort).
-
-To evaluate the verification result in the ACL
-a large number of expansion variables
-containing the signature status and its details are set up during the
-runtime of the ACL.
-
-Calling the ACL only for existing signatures is not sufficient to build
-more advanced policies. For that reason, the main option
-&%dkim_verify_signers%&, and an expansion variable
-&%$dkim_signers%& exist.
-
-The main option &%dkim_verify_signers%& can be set to a colon-separated
-list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is
-called. It is expanded when the message has been received. At this point,
-the expansion variable &%$dkim_signers%& already contains a colon-separated
-list of signer domains and identities for the message. When
-&%dkim_verify_signers%& is not specified in the main configuration,
-it defaults as:
-.code
-dkim_verify_signers = $dkim_signers
-.endd
-This leads to the default behaviour of calling &%acl_smtp_dkim%& for each
-DKIM signature in the message. Current DKIM verifiers may want to explicitly
-call the ACL for known domains or identities. This would be achieved as follows:
-.code
-dkim_verify_signers = paypal.com:ebay.com:$dkim_signers
-.endd
-This would result in &%acl_smtp_dkim%& always being called for "paypal.com"
-and "ebay.com", plus all domains and identities that have signatures in the message.
-You can also be more creative in constructing your policy. For example:
-.code
-dkim_verify_signers = $sender_address_domain:$dkim_signers
-.endd
-
-If a domain or identity is listed several times in the (expanded) value of
-&%dkim_verify_signers%&, the ACL is only called once for that domain or identity.
-
-Note that if the option is set using untrustworthy data
-(such as the From: header)
-care should be taken to force lowercase for domains
-and for the domain part if identities.
-The default setting can be regarded as trustworthy in this respect.
-
-If multiple signatures match a domain (or identity), the ACL is called once
-for each matching signature.
-
-
-Inside the DKIM ACL, the following expansion variables are
-available (from most to least important):
-
-
-.vlist
-.vitem &%$dkim_cur_signer%&
-The signer that is being evaluated in this ACL run. This can be a domain or
-an identity. This is one of the list items from the expanded main option
-&%dkim_verify_signers%& (see above).
-
-.vitem &%$dkim_verify_status%&
-Within the DKIM ACL,
-a string describing the general status of the signature. One of
-.ilist
-&%none%&: There is no signature in the message for the current domain or
-identity (as reflected by &%$dkim_cur_signer%&).
-.next
-&%invalid%&: The signature could not be verified due to a processing error.
-More detail is available in &%$dkim_verify_reason%&.
-.next
-&%fail%&: Verification of the signature failed.  More detail is
-available in &%$dkim_verify_reason%&.
-.next
-&%pass%&: The signature passed verification. It is valid.
-.endlist
-
-This variable can be overwritten using an ACL 'set' modifier.
-This might, for instance, be done to enforce a policy restriction on
-hash-method or key-size:
-.code
-  warn condition       = ${if eq {$dkim_verify_status}{pass}}
-       condition       = ${if eq {${length_3:$dkim_algo}}{rsa}}
-       condition       = ${if or {{eq {$dkim_algo}{rsa-sha1}} \
-                                  {< {$dkim_key_length}{1024}}}}
-       logwrite        = NOTE: forcing DKIM verify fail (was pass)
-       set dkim_verify_status = fail
-       set dkim_verify_reason = hash too weak or key too short
-.endd
-
-So long as a DKIM ACL is defined (it need do no more than accept),
-after all the DKIM ACL runs have completed, the value becomes a
-colon-separated list of the values after each run.
-This is maintained for the mime, prdr and data ACLs.
-
-.vitem &%$dkim_verify_reason%&
-A string giving a little bit more detail when &%$dkim_verify_status%& is either
-"fail" or "invalid". One of
-.ilist
-&%pubkey_unavailable%& (when &%$dkim_verify_status%&="invalid"): The public
-key for the domain could not be retrieved. This may be a temporary problem.
-.next
-&%pubkey_syntax%& (when &%$dkim_verify_status%&="invalid"): The public key
-record for the domain is syntactically invalid.
-.next
-&%bodyhash_mismatch%& (when &%$dkim_verify_status%&="fail"): The calculated
-body hash does not match the one specified in the signature header. This
-means that the message body was modified in transit.
-.next
-&%signature_incorrect%& (when &%$dkim_verify_status%&="fail"): The signature
-could not be verified. This may mean that headers were modified,
-re-written or otherwise changed in a way which is incompatible with
-DKIM verification. It may of course also mean that the signature is forged.
-.endlist
-
-This variable can be overwritten, with any value, using an ACL 'set' modifier.
-
-.vitem &%$dkim_domain%&
-The signing domain. IMPORTANT: This variable is only populated if there is
-an actual signature in the message for the current domain or identity (as
-reflected by &%$dkim_cur_signer%&).
-
-.vitem &%$dkim_identity%&
-The signing identity, if present. IMPORTANT: This variable is only populated
-if there is an actual signature in the message for the current domain or
-identity (as reflected by &%$dkim_cur_signer%&).
-
-.vitem &%$dkim_selector%&
-The key record selector string.
-
-.vitem &%$dkim_algo%&
-The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'.
-If running under GnuTLS 3.6.0 or OpenSSL 1.1.1 or later,
-may also be 'ed25519-sha256'.
-The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
-for EC keys.
-
-Note that RFC 8301 says:
-.code
-rsa-sha1 MUST NOT be used for signing or verifying.
-
-DKIM signatures identified as having been signed with historic
-algorithms (currently, rsa-sha1) have permanently failed evaluation
-.endd
-
-To enforce this you must either have a DKIM ACL which checks this variable
-and overwrites the &$dkim_verify_status$& variable as discussed above,
-or have set the main option &%dkim_verify_hashes%& to exclude
-processing of such signatures.
-
-.vitem &%$dkim_canon_body%&
-The body canonicalization method. One of 'relaxed' or 'simple'.
-
-.vitem &%$dkim_canon_headers%&
-The header canonicalization method. One of 'relaxed' or 'simple'.
-
-.vitem &%$dkim_copiedheaders%&
-A transcript of headers and their values which are included in the signature
-(copied from the 'z=' tag of the signature).
-Note that RFC6376 requires that verification fail if the From: header is
-not included in the signature.  Exim does not enforce this; sites wishing
-strict enforcement should code the check explicitly.
-
-.vitem &%$dkim_bodylength%&
-The number of signed body bytes. If zero ("0"), the body is unsigned. If no
-limit was set by the signer, "9999999999999" is returned. This makes sure
-that this variable always expands to an integer value.
-&*Note:*& The presence of the signature tag specifying a signing body length
-is one possible route to spoofing of valid DKIM signatures.
-A paranoid implementation might wish to regard signature where this variable
-shows less than the "no limit" return as being invalid.
-
-.vitem &%$dkim_created%&
-UNIX timestamp reflecting the date and time when the signature was created.
-When this was not specified by the signer, "0" is returned.
-
-.vitem &%$dkim_expires%&
-UNIX timestamp reflecting the date and time when the signer wants the
-signature to be treated as "expired". When this was not specified by the
-signer, "9999999999999" is returned. This makes it possible to do useful
-integer size comparisons against this value.
-Note that Exim does not check this value.
-
-.vitem &%$dkim_headernames%&
-A colon-separated list of names of headers included in the signature.
-
-.vitem &%$dkim_key_testing%&
-"1" if the key record has the "testing" flag set, "0" if not.
-
-.vitem &%$dkim_key_nosubdomains%&
-"1" if the key record forbids subdomaining, "0" otherwise.
-
-.vitem &%$dkim_key_srvtype%&
-Service type (tag s=) from the key record. Defaults to "*" if not specified
-in the key record.
-
-.vitem &%$dkim_key_granularity%&
-Key granularity (tag g=) from the key record. Defaults to "*" if not specified
-in the key record.
-
-.vitem &%$dkim_key_notes%&
-Notes from the key record (tag n=).
-
-.vitem &%$dkim_key_length%&
-Number of bits in the key.
-
-Note that RFC 8301 says:
-.code
-Verifiers MUST NOT consider signatures using RSA keys of
-less than 1024 bits as valid signatures.
-.endd
-
-To enforce this you must have a DKIM ACL which checks this variable
-and overwrites the &$dkim_verify_status$& variable as discussed above.
-As EC keys are much smaller, the check should only do this for RSA keys.
-
-.endlist
-
-In addition, two ACL conditions are provided:
-
-.vlist
-.vitem &%dkim_signers%&
-ACL condition that checks a colon-separated list of domains or identities
-for a match against the domain or identity that the ACL is currently verifying
-(reflected by &%$dkim_cur_signer%&). This is typically used to restrict an ACL
-verb to a group of domains or identities. For example:
-
-.code
-# Warn when Mail purportedly from GMail has no gmail signature
-warn log_message = GMail sender without gmail.com DKIM signature
-     sender_domains = gmail.com
-     dkim_signers = gmail.com
-     dkim_status = none
-.endd
-
-Note that the above does not check for a total lack of DKIM signing;
-for that check for empty &$h_DKIM-Signature:$& in the data ACL.
-
-.vitem &%dkim_status%&
-ACL condition that checks a colon-separated list of possible DKIM verification
-results against the actual result of verification. This is typically used
-to restrict an ACL verb to a list of verification outcomes, for example:
-
-.code
-deny message = Mail from Paypal with invalid/missing signature
-     sender_domains = paypal.com:paypal.de
-     dkim_signers = paypal.com:paypal.de
-     dkim_status = none:invalid:fail
-.endd
-
-The possible status keywords are: 'none','invalid','fail' and 'pass'. Please
-see the documentation of the &%$dkim_verify_status%& expansion variable above
-for more information of what they mean.
-.endlist
-
-
-
-
-.section "SPF (Sender Policy Framework)" SECSPF
-.cindex SPF verification
-
-SPF is a mechanism whereby a domain may assert which IP addresses may transmit
-messages with its domain in the envelope from, documented by RFC 7208.
-For more information on SPF see &url(http://www.open-spf.org), a static copy of
-the &url(http://openspf.org).
-. --- 2019-10-28: still not https, open-spf.org is told to be a
-. --- web-archive copy of the now dead openspf.org site
-. --- See https://www.mail-archive.com/mailop@mailop.org/msg08019.html for a
-. --- discussion.
-
-Messages sent by a system not authorised will fail checking of such assertions.
-This includes retransmissions done by traditional forwarders.
-
-SPF verification support is built into Exim if SUPPORT_SPF=yes is set in
-&_Local/Makefile_&.  The support uses the &_libspf2_& library
-&url(https://www.libspf2.org/).
-There is no Exim involvement in the transmission of messages;
-publishing certain DNS records is all that is required.
-
-For verification, an ACL condition and an expansion lookup are provided.
-.cindex authentication "expansion item"
-Performing verification sets up information used by the
-&%authresults%& expansion item.
-
-
-.cindex SPF "ACL condition"
-.cindex ACL "spf condition"
-The ACL condition "spf" can be used at or after the MAIL ACL.
-It takes as an argument a list of strings giving the outcome of the SPF check,
-and will succeed for any matching outcome.
-Valid strings are:
-.vlist
-.vitem &%pass%&
-The SPF check passed, the sending host is positively verified by SPF.
-
-.vitem &%fail%&
-The SPF check failed, the sending host is NOT allowed to send mail for the
-domain in the envelope-from address.
-
-.vitem &%softfail%&
-The SPF check failed, but the queried domain can't absolutely confirm that this
-is a forgery.
-
-.vitem &%none%&
-The queried domain does not publish SPF records.
-
-.vitem &%neutral%&
-The SPF check returned a "neutral" state.  This means the queried domain has
-published a SPF record, but wants to allow outside servers to send mail under
-its domain as well.  This should be treated like "none".
-
-.vitem &%permerror%&
-This indicates a syntax error in the SPF record of the queried domain.
-You may deny messages when this occurs.
-
-.vitem &%temperror%&
-This indicates a temporary error during all processing, including Exim's
-SPF processing.  You may defer messages when this occurs.
-.endlist
-
-You can prefix each string with an exclamation mark to  invert
-its meaning,  for example  "!fail" will  match all  results but
-"fail".  The  string  list is  evaluated  left-to-right,  in a
-short-circuit fashion.
-
-Example:
-.code
-deny spf = fail
-     message = $sender_host_address is not allowed to send mail from \
-               ${if def:sender_address_domain \
-                    {$sender_address_domain}{$sender_helo_name}}.  \
-               Please see http://www.open-spf.org/Why?scope=\
-               ${if def:sender_address_domain {mfrom}{helo}};\
-               identity=${if def:sender_address_domain \
-                             {$sender_address}{$sender_helo_name}};\
-               ip=$sender_host_address
-.endd
-
-When the spf condition has run, it sets up several expansion
-variables:
-
-.cindex SPF "verification variables"
-.vlist
-.vitem &$spf_header_comment$&
-.vindex &$spf_header_comment$&
-  This contains a human-readable string describing the outcome
-  of the SPF check. You can add it to a custom header or use
-  it for logging purposes.
-
-.vitem &$spf_received$&
-.vindex &$spf_received$&
-  This contains a complete Received-SPF: header that can be
-  added to the message. Please note that according to the SPF
-  draft, this header must be added at the top of the header
-  list. Please see section 10 on how you can do this.
-
-  Note: in case of "Best-guess" (see below), the convention is
-  to put this string in a header called X-SPF-Guess: instead.
-
-.vitem &$spf_result$&
-.vindex &$spf_result$&
-  This contains the outcome of the SPF check in string form,
-  one of pass, fail, softfail, none, neutral, permerror or
-  temperror.
-
-.vitem &$spf_result_guessed$&
-.vindex &$spf_result_guessed$&
-  This boolean is true only if a best-guess operation was used
-  and required in order to obtain a result.
-
-.vitem &$spf_smtp_comment$&
-.vindex &$spf_smtp_comment$&
-  This contains a string that can be used in a SMTP response
-  to the calling party. Useful for "fail".
-.endlist
-
-
-.cindex SPF "ACL condition"
-.cindex ACL "spf_guess condition"
-.cindex SPF "best guess"
-In addition to SPF, you can also perform checks for so-called
-"Best-guess".  Strictly speaking, "Best-guess" is not standard
-SPF, but it is supported by the same framework that enables SPF
-capability.
-Refer to &url(http://www.open-spf.org/FAQ/Best_guess_record)
-for a description of what it means.
-. --- 2019-10-28: still not https:
-
-To access this feature, simply use the spf_guess condition in place
-of the spf one.  For example:
-
-.code
-deny spf_guess = fail
-     message = $sender_host_address doesn't look trustworthy to me
-.endd
-
-In case you decide to reject messages based on this check, you
-should note that although it uses the same framework, "Best-guess"
-is not SPF, and therefore you should not mention SPF at all in your
-reject message.
-
-When the spf_guess condition has run, it sets up the same expansion
-variables as when spf condition is run, described above.
-
-Additionally, since Best-guess is not standardized, you may redefine
-what "Best-guess" means to you by redefining the main configuration
-&%spf_guess%& option.
-For example, the following:
-
-.code
-spf_guess = v=spf1 a/16 mx/16 ptr ?all
-.endd
-
-would relax host matching rules to a broader network range.
-
-
-.cindex SPF "lookup expansion"
-.cindex lookup spf
-A lookup expansion is also available. It takes an email
-address as the key and an IP address
-(v4 or v6)
-as the database:
-
-.code
-  ${lookup {username@domain} spf {ip.ip.ip.ip}}
-.endd
-
-The lookup will return the same result strings as can appear in
-&$spf_result$& (pass,fail,softfail,neutral,none,err_perm,err_temp).
-
-
-
-
-
-.section DMARC SECDMARC
-.cindex DMARC verification
-
-DMARC combines feedback from SPF, DKIM, and header From: in order
-to attempt to provide better indicators of the authenticity of an
-email.  This document does not explain the fundamentals; you
-should read and understand how it works by visiting the website at
-&url(http://www.dmarc.org/).
-
-If Exim is built with DMARC support,
-the libopendmarc library is used.
-
-For building Exim yourself, obtain the library from
-&url(http://sourceforge.net/projects/opendmarc/)
-to obtain a copy, or find it in your favorite package
-repository.  You will need to attend to the local/Makefile feature
-SUPPORT_DMARC and the associated LDFLAGS addition.
-This description assumes
-that headers will be in /usr/local/include, and that the libraries
-are in /usr/local/lib.
-
-. subsection
-
-There are three main-configuration options:
-.cindex DMARC "configuration options"
-
-The &%dmarc_tld_file%& option
-.oindex &%dmarc_tld_file%&
-defines the location of a text file of valid
-top level domains the opendmarc library uses
-during domain parsing. Maintained by Mozilla,
-the most current version can be downloaded
-from a link at &url(https://publicsuffix.org/list/public_suffix_list.dat).
-See also the util/renew-opendmarc-tlds.sh script.
-.new
-The default for the option is unset.
-If not set, DMARC processing is disabled.
-.wen
-
-
-The &%dmarc_history_file%& option, if set
-.oindex &%dmarc_history_file%&
-defines the location of a file to log results
-of dmarc verification on inbound emails. The
-contents are importable by the opendmarc tools
-which will manage the data, send out DMARC
-reports, and expire the data. Make sure the
-directory of this file is writable by the user
-exim runs as.
-The default is unset.
-
-The &%dmarc_forensic_sender%& option
-.oindex &%dmarc_forensic_sender%&
-defines an alternate email address to use when sending a
-forensic report detailing alignment failures
-if a sender domain's dmarc record specifies it
-and you have configured Exim to send them.
-If set, this is expanded and used for the
-From: header line; the address is extracted
-from it and used for the envelope from.
-If not set (the default), the From: header is expanded from
-the dsn_from option, and <> is used for the
-envelope from.
-
-. I wish we had subsections...
-
-.cindex DMARC controls
-By default, the DMARC processing will run for any remote,
-non-authenticated user.  It makes sense to only verify DMARC
-status of messages coming from remote, untrusted sources.  You can
-use standard conditions such as hosts, senders, etc, to decide that
-DMARC verification should *not* be performed for them and disable
-DMARC with an ACL control modifier:
-.code
-  control = dmarc_disable_verify
-.endd
-A DMARC record can also specify a "forensic address", which gives
-exim an email address to submit reports about failed alignment.
-Exim does not do this by default because in certain conditions it
-results in unintended information leakage (what lists a user might
-be subscribed to, etc).  You must configure exim to submit forensic
-reports to the owner of the domain.  If the DMARC record contains a
-forensic address and you specify the control statement below, then
-exim will send these forensic emails.  It is also advised that you
-configure a &%dmarc_forensic_sender%& because the default sender address
-construction might be inadequate.
-.code
-  control = dmarc_enable_forensic
-.endd
-(AGAIN: You can choose not to send these forensic reports by simply
-not putting the dmarc_enable_forensic control line at any point in
-your exim config.  If you don't tell exim to send them, it will not
-send them.)
-
-There are no options to either control.  Both must appear before
-the DATA acl.
-
-. subsection
-
-DMARC checks cam be run on incoming SMTP  messages by using the
-&"dmarc_status"& ACL condition in the DATA ACL.  You are required to
-call the &"spf"& condition first in the ACLs, then the &"dmarc_status"&
-condition.  Putting this condition in the ACLs is required in order
-for a DMARC check to actually occur.  All of the variables are set
-up before the DATA ACL, but there is no actual DMARC check that
-occurs until a &"dmarc_status"& condition is encountered in the ACLs.
-
-The &"dmarc_status"& condition takes a list of strings on its
-right-hand side.  These strings describe recommended action based
-on the DMARC check.  To understand what the policy recommendations
-mean, refer to the DMARC website above.  Valid strings are:
-.display
-&'accept      '& The DMARC check passed and the library recommends accepting the email.
-&'reject      '& The DMARC check failed and the library recommends rejecting the email.
-&'quarantine  '& The DMARC check failed and the library recommends keeping it for further inspection.
-&'none        '& The DMARC check passed and the library recommends no specific action, neutral.
-&'norecord    '& No policy section in the DMARC record for this sender domain.
-&'nofrom      '& Unable to determine the domain of the sender.
-&'temperror   '& Library error or dns error.
-&'off         '& The DMARC check was disabled for this email.
-.endd
-You can prefix each string with an exclamation mark to invert its
-meaning, for example "!accept" will match all results but
-"accept".  The string list is evaluated left-to-right in a
-short-circuit fashion.  When a string matches the outcome of the
-DMARC check, the condition succeeds.  If none of the listed
-strings matches the outcome of the DMARC check, the condition
-fails.
-
-Of course, you can also use any other lookup method that Exim
-supports, including LDAP, Postgres, MySQL, etc, as long as the
-result is a list of colon-separated strings.
-
-Performing the check sets up information used by the
-&%authresults%& expansion item.
-
-Several expansion variables are set before the DATA ACL is
-processed, and you can use them in this ACL.  The following
-expansion variables are available:
-
-.vlist
-.vitem &$dmarc_status$&
-.vindex &$dmarc_status$&
-.cindex DMARC result
-A one word status indicating what the DMARC library
-thinks of the email.  It is a combination of the results of
-DMARC record lookup and the SPF/DKIM/DMARC processing results
-(if a DMARC record was found).  The actual policy declared
-in the DMARC record is in a separate expansion variable.
-
-.vitem &$dmarc_status_text$&
-.vindex &$dmarc_status_text$&
-Slightly longer, human readable status.
-
-.vitem &$dmarc_used_domain$&
-.vindex &$dmarc_used_domain$&
-The domain which DMARC used to look up the DMARC policy record.
-
-.vitem &$dmarc_domain_policy$&
-.vindex &$dmarc_domain_policy$&
-The policy declared in the DMARC record.  Valid values
-are "none", "reject" and "quarantine".  It is blank when there
-is any error, including no DMARC record.
-.endlist
-
-. subsection
-
-By default, Exim's DMARC configuration is intended to be
-non-intrusive and conservative.  To facilitate this, Exim will not
-create any type of logging files without explicit configuration by
-you, the admin.  Nor will Exim send out any emails/reports about
-DMARC issues without explicit configuration by you, the admin (other
-than typical bounce messages that may come about due to ACL
-processing or failure delivery issues).
-
-In order to log statistics suitable to be imported by the opendmarc
-tools, you need to:
-.ilist
-Configure the global option &%dmarc_history_file%&
-.next
-Configure cron jobs to call the appropriate opendmarc history
-import scripts and truncating the dmarc_history_file
-.endlist
-
-In order to send forensic reports, you need to:
-.ilist
-Configure the global option &%dmarc_forensic_sender%&
-.next
-Configure, somewhere before the DATA ACL, the control option to
-enable sending DMARC forensic reports
-.endlist
-
-. subsection
-
-Example usage:
-.code
-(RCPT ACL)
-  warn    domains        = +local_domains
-          hosts          = +local_hosts
-          control        = dmarc_disable_verify
-
-  warn    !domains       = +screwed_up_dmarc_records
-          control        = dmarc_enable_forensic
-
-  warn    condition      = (lookup if destined to mailing list)
-          set acl_m_mailing_list = 1
-
-(DATA ACL)
-  warn    dmarc_status   = accept : none : off
-          !authenticated = *
-          log_message    = DMARC DEBUG: $dmarc_status $dmarc_used_domain
-
-  warn    dmarc_status   = !accept
-          !authenticated = *
-          log_message    = DMARC DEBUG: '$dmarc_status' for $dmarc_used_domain
-
-  warn    dmarc_status   = quarantine
-          !authenticated = *
-          set $acl_m_quarantine = 1
-          # Do something in a transport with this flag variable
-
-  deny    condition      = ${if eq{$dmarc_domain_policy}{reject}}
-          condition      = ${if eq{$acl_m_mailing_list}{1}}
-          message        = Messages from $dmarc_used_domain break mailing lists
-
-  deny    dmarc_status   = reject
-          !authenticated = *
-          message        = Message from $dmarc_used_domain failed sender's DMARC policy, REJECT
-
-  warn    add_header     = :at_start:${authresults {$primary_hostname}}
-.endd
-
-
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "Proxies" "CHAPproxies" &&&
-         "Proxy support"
-.cindex "proxy support"
-.cindex "proxy" "access via"
-
-A proxy is an intermediate system through which communication is passed.
-Proxies may provide a security, availability or load-distribution function.
-
-
-.section "Inbound proxies" SECTproxyInbound
-.cindex proxy inbound
-.cindex proxy "server side"
-.cindex proxy "Proxy protocol"
-.cindex "Proxy protocol" proxy
-
-Exim has support for receiving inbound SMTP connections via a proxy
-that uses &"Proxy Protocol"& to speak to it.
-To include this support, include &"SUPPORT_PROXY=yes"&
-in Local/Makefile.
-
-It was built on the HAProxy specification, found at
-&url(https://www.haproxy.org/download/1.8/doc/proxy-protocol.txt).
-
-The purpose of this facility is so that an application load balancer,
-such as HAProxy, can sit in front of several Exim servers
-to distribute load.
-Exim uses the local protocol communication with the proxy to obtain
-the remote SMTP system IP address and port information.
-There is no logging if a host passes or
-fails Proxy Protocol negotiation, but it can easily be determined and
-recorded in an ACL (example is below).
-
-Use of a proxy is enabled by setting the &%hosts_proxy%&
-main configuration option to a hostlist; connections from these
-hosts will use Proxy Protocol.
-Exim supports both version 1 and version 2 of the Proxy Protocol and
-automatically determines which version is in use.
-
-The Proxy Protocol header is the first data received on a TCP connection
-and is inserted before any TLS-on-connect handshake from the client; Exim
-negotiates TLS between Exim-as-server and the remote client, not between
-Exim and the proxy server.
-
-The following expansion variables are usable
-(&"internal"& and &"external"& here refer to the interfaces
-of the proxy):
-.display
-&'proxy_external_address   '& IP of host being proxied or IP of remote interface of proxy
-&'proxy_external_port      '& Port of host being proxied or Port on remote interface of proxy
-&'proxy_local_address      '& IP of proxy server inbound or IP of local interface of proxy
-&'proxy_local_port         '& Port of proxy server inbound or Port on local interface of proxy
-&'proxy_session            '& boolean: SMTP connection via proxy
-.endd
-If &$proxy_session$& is set but &$proxy_external_address$& is empty
-there was a protocol error.
-The variables &$sender_host_address$& and &$sender_host_port$&
-will have values for the actual client system, not the proxy.
-
-Since the real connections are all coming from the proxy, and the
-per host connection tracking is done before Proxy Protocol is
-evaluated, &%smtp_accept_max_per_host%& must be set high enough to
-handle all of the parallel volume you expect per inbound proxy.
-With the option set so high, you lose the ability
-to protect your server from many connections from one IP.
-In order to prevent your server from overload, you
-need to add a per connection ratelimit to your connect ACL.
-A possible solution is:
-.display
-  # Set max number of connections per host
-  LIMIT   = 5
-  # Or do some kind of IP lookup in a flat file or database
-  # LIMIT = ${lookup{$sender_host_address}iplsearch{/etc/exim/proxy_limits}}
-
-  defer   message        = Too many connections from this IP right now
-          ratelimit      = LIMIT / 5s / per_conn / strict
-.endd
-
-
-
-.section "Outbound proxies" SECTproxySOCKS
-.cindex proxy outbound
-.cindex proxy "client side"
-.cindex proxy SOCKS
-.cindex SOCKS proxy
-Exim has support for sending outbound SMTP via a proxy
-using a protocol called SOCKS5 (defined by RFC1928).
-The support can be optionally included by defining SUPPORT_SOCKS=yes in
-Local/Makefile.
-
-Use of a proxy is enabled by setting the &%socks_proxy%& option
-on an smtp transport.
-The option value is expanded and should then be a list
-(colon-separated by default) of proxy specifiers.
-Each proxy specifier is a list
-(space-separated by default) where the initial element
-is an IP address and any subsequent elements are options.
-
-Options are a string <name>=<value>.
-The list of options is in the following table:
-.display
-&'auth   '& authentication method
-&'name   '& authentication username
-&'pass   '& authentication password
-&'port   '& tcp port
-&'tmo    '& connection timeout
-&'pri    '& priority
-&'weight '& selection bias
-.endd
-
-More details on each of these options follows:
-
-.ilist
-.cindex authentication "to proxy"
-.cindex proxy authentication
-&%auth%&: Either &"none"& (default) or &"name"&.
-Using &"name"& selects username/password authentication per RFC 1929
-for access to the proxy.
-Default is &"none"&.
-.next
-&%name%&: sets the username for the &"name"& authentication method.
-Default is empty.
-.next
-&%pass%&: sets the password for the &"name"& authentication method.
-Default is empty.
-.next
-&%port%&: the TCP port number to use for the connection to the proxy.
-Default is 1080.
-.next
-&%tmo%&: sets a connection timeout in seconds for this proxy.
-Default is 5.
-.next
-&%pri%&: specifies a priority for the proxy within the list,
-higher values being tried first.
-The default priority is 1.
-.next
-&%weight%&: specifies a selection bias.
-Within a priority set servers are queried in a random fashion,
-weighted by this value.
-The default value for selection bias is 1.
-.endlist
-
-Proxies from the list are tried according to their priority
-and weight settings until one responds.  The timeout for the
-overall connection applies to the set of proxied attempts.
-
-.section Logging SECTproxyLog
-To log the (local) IP of a proxy in the incoming or delivery logline,
-add &"+proxy"& to the &%log_selector%& option.
-This will add a component tagged with &"PRX="& to the line.
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "Internationalisation" "CHAPi18n" &&&
-         "Internationalisation""
-.cindex internationalisation "email address"
-.cindex EAI
-.cindex i18n
-.cindex utf8 "mail name handling"
-
-Exim has support for Internationalised mail names.
-To include this it must be built with SUPPORT_I18N and the libidn library.
-Standards supported are RFCs 2060, 5890, 6530 and 6533.
-
-If Exim is built with SUPPORT_I18N_2008 (in addition to SUPPORT_I18N, not
-instead of it) then IDNA2008 is supported; this adds an extra library
-requirement, upon libidn2.
-
-.section "MTA operations" SECTi18nMTA
-.cindex SMTPUTF8 "ESMTP option"
-The main configuration option &%smtputf8_advertise_hosts%& specifies
-a host list.  If this matches the sending host and
-accept_8bitmime is true (the default) then the ESMTP option
-SMTPUTF8 will be advertised.
-
-If the sender specifies the SMTPUTF8 option on a MAIL command
-international handling for the message is enabled and
-the expansion variable &$message_smtputf8$& will have value TRUE.
-
-The option &%allow_utf8_domains%& is set to true for this
-message. All DNS lookups are converted to a-label form
-whatever the setting of &%allow_utf8_domains%&
-when Exim is built with SUPPORT_I18N.
-
-Both localparts and domain are maintained as the original
-UTF-8 form internally; any comparison or regular-expression use will
-require appropriate care.  Filenames created, eg. by
-the appendfile transport, will have UTF-8 names.
-
-HELO names sent by the smtp transport will have any UTF-8
-components expanded to a-label form,
-and any certificate name checks will be done using the a-label
-form of the name.
-
-.cindex log protocol
-.cindex SMTPUTF8 logging
-.cindex i18n logging
-Log lines and Received-by: header lines will acquire a "utf8"
-prefix on the protocol element, eg. utf8esmtp.
-
-The following expansion operators can be used:
-.code
-${utf8_domain_to_alabel:str}
-${utf8_domain_from_alabel:str}
-${utf8_localpart_to_alabel:str}
-${utf8_localpart_from_alabel:str}
-.endd
-
-.cindex utf8 "address downconversion"
-.cindex i18n "utf8 address downconversion"
-The RCPT ACL
-may use the following modifier:
-.display
-control = utf8_downconvert
-control = utf8_downconvert/<value>
-.endd
-This sets a flag requiring that addresses are converted to
-a-label form before smtp delivery, for use in a
-Message Submission Agent context.
-If a value is appended it may be:
-.display
-&`1  `& (default) mandatory downconversion
-&`0  `& no downconversion
-&`-1 `& if SMTPUTF8 not supported by destination host
-.endd
-
-If mua_wrapper is set, the utf8_downconvert control
-is initially set to -1.
-
-The smtp transport has an option &%utf8_downconvert%&.
-If set it must expand to one of the three values described above,
-and it overrides any previously set value.
-
-
-There is no explicit support for VRFY and EXPN.
-Configurations supporting these should inspect
-&$smtp_command_argument$& for an SMTPUTF8 argument.
-
-There is no support for LMTP on Unix sockets.
-Using the "lmtp" protocol option on an smtp transport,
-for LMTP over TCP, should work as expected.
-
-There is no support for DSN unitext handling,
-and no provision for converting logging from or to UTF-8.
-
-
-
-.section "MDA operations" SECTi18nMDA
-To aid in constructing names suitable for IMAP folders
-the following expansion operator can be used:
-.code
-${imapfolder {<string>} {<sep>} {<specials>}}
-.endd
-
-The string is converted from the charset specified by
-the "headers charset" command (in a filter file)
-or &%headers_charset%& main configuration option (otherwise),
-to the
-modified UTF-7 encoding specified by RFC 2060,
-with the following exception: All occurrences of <sep>
-(which has to be a single character)
-are replaced with periods ("."), and all periods and slashes that are not
-<sep> and are not in the <specials> string are BASE64 encoded.
-
-The third argument can be omitted, defaulting to an empty string.
-The second argument can be omitted, defaulting to "/".
-
-This is the encoding used by Courier for Maildir names on disk, and followed
-by many other IMAP servers.
-
-Examples:
-.display
-&`${imapfolder {Foo/Bar}}       `& yields &`Foo.Bar`&
-&`${imapfolder {Foo/Bar}{.}{/}} `& yields &`Foo&&AC8-Bar`&
-&`${imapfolder {Räksmörgås}}    `& yields &`R&&AOQ-ksm&&APY-rg&&AOU-s`&
-.endd
-
-Note that the source charset setting is vital, and also that characters
-must be representable in UTF-16.
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "Events" "CHAPevents" &&&
-         "Events"
-.cindex events
-
-The events mechanism in Exim can be used to intercept processing at a number
-of points.  It was originally invented to give a way to do customised logging
-actions (for example, to a database) but can also be used to modify some
-processing actions.
-
-Most installations will never need to use Events.
-The support can be left out of a build by defining DISABLE_EVENT=yes
-in &_Local/Makefile_&.
-
-There are two major classes of events: main and transport.
-The main configuration option &%event_action%& controls reception events;
-a transport option &%event_action%& controls delivery events.
-
-Both options are a string which is expanded when the event fires.
-An example might look like:
-.cindex logging custom
-.code
-event_action = ${if eq {msg:delivery}{$event_name} \
-{${lookup pgsql {SELECT * FROM record_Delivery( \
-    '${quote_pgsql:$sender_address_domain}',\
-    '${quote_pgsql:${lc:$sender_address_local_part}}', \
-    '${quote_pgsql:$domain}', \
-    '${quote_pgsql:${lc:$local_part}}', \
-    '${quote_pgsql:$host_address}', \
-    '${quote_pgsql:${lc:$host}}', \
-    '${quote_pgsql:$message_exim_id}')}} \
-} {}}
-.endd
-
-Events have names which correspond to the point in process at which they fire.
-The name is placed in the variable &$event_name$& and the event action
-expansion must check this, as it will be called for every possible event type.
-
-.new
-The current list of events is:
-.wen
-.display
-&`dane:fail              after    transport  `& per connection
-&`msg:complete           after    main       `& per message
-&`msg:defer              after    transport  `& per message per delivery try
-&`msg:delivery           after    transport  `& per recipient
-&`msg:rcpt:host:defer    after    transport  `& per recipient per host
-&`msg:rcpt:defer         after    transport  `& per recipient
-&`msg:host:defer         after    transport  `& per host per delivery try; host errors
-&`msg:fail:delivery      after    transport  `& per recipient
-&`msg:fail:internal      after    main       `& per recipient
-&`tcp:connect            before   transport  `& per connection
-&`tcp:close              after    transport  `& per connection
-&`tls:cert               before   both       `& per certificate in verification chain
-&`smtp:connect           after    transport  `& per connection
-&`smtp:ehlo              after    transport  `& per connection
-.endd
-New event types may be added in future.
-
-The event name is a colon-separated list, defining the type of
-event in a tree of possibilities.  It may be used as a list
-or just matched on as a whole.  There will be no spaces in the name.
-
-The second column in the table above describes whether the event fires
-before or after the action is associates with.  Those which fire before
-can be used to affect that action (more on this below).
-
-The third column in the table above says what section of the configuration
-should define the event action.
-
-An additional variable, &$event_data$&, is filled with information varying
-with the event type:
-.display
-&`dane:fail            `& failure reason
-&`msg:defer            `& error string
-&`msg:delivery         `& smtp confirmation message
-&`msg:fail:internal    `& failure reason
-&`msg:fail:delivery    `& smtp error message
-&`msg:host:defer       `& error string
-&`msg:rcpt:host:defer  `& error string
-&`msg:rcpt:defer       `& error string
-&`tls:cert             `& verification chain depth
-&`smtp:connect         `& smtp banner
-&`smtp:ehlo            `& smtp ehlo response
-.endd
-
-The :defer events populate one extra variable: &$event_defer_errno$&.
-
-For complex operations an ACL expansion can be used in &%event_action%&
-however due to the multiple contexts that Exim operates in during
-the course of its processing:
-.ilist
-variables set in transport events will not be visible outside that
-transport call
-.next
-acl_m variables in a server context are lost on a new connection,
-and after smtp helo/ehlo/mail/starttls/rset commands
-.endlist
-Using an ACL expansion with the logwrite modifier can be
-a useful way of writing to the main log.
-
-The expansion of the event_action option should normally
-return an empty string.  Should it return anything else the
-following will be forced:
-.display
-&`tcp:connect      `&  do not connect
-&`tls:cert         `&  refuse verification
-&`smtp:connect     `&  close connection
-.endd
-All other message types ignore the result string, and
-no other use is made of it.
-
-For a tcp:connect event, if the connection is being made to a proxy
-then the address and port variables will be that of the proxy and not
-the target system.
-
-For tls:cert events, if GnuTLS is in use this will trigger only per
-chain element received on the connection.
-For OpenSSL it will trigger for every chain element including those
-loaded locally.
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-.chapter "Adding new drivers or lookup types" "CHID13" &&&
-         "Adding drivers or lookups"
-.cindex "adding drivers"
-.cindex "new drivers, adding"
-.cindex "drivers" "adding new"
-The following actions have to be taken in order to add a new router, transport,
-authenticator, or lookup type to Exim:
-
-.olist
-Choose a name for the driver or lookup type that does not conflict with any
-existing name; I will use &"newdriver"& in what follows.
-.next
-Add to &_src/EDITME_& the line:
-.display
-<&'type'&>&`_NEWDRIVER=yes`&
-.endd
-where <&'type'&> is ROUTER, TRANSPORT, AUTH, or LOOKUP. If the
-code is not to be included in the binary by default, comment this line out. You
-should also add any relevant comments about the driver or lookup type.
-.next
-Add to &_src/config.h.defaults_& the line:
-.code
-#define <type>_NEWDRIVER
-.endd
-.next
-Edit &_src/drtables.c_&, adding conditional code to pull in the private header
-and create a table entry as is done for all the other drivers and lookup types.
-.next
-Edit &_scripts/lookups-Makefile_& if this is a new lookup; there is a for-loop
-near the bottom, ranging the &`name_mod`& variable over a list of all lookups.
-Add your &`NEWDRIVER`& to that list.
-As long as the dynamic module would be named &_newdriver.so_&, you can use the
-simple form that most lookups have.
-.next
-Edit &_Makefile_& in the appropriate sub-directory (&_src/routers_&,
-&_src/transports_&, &_src/auths_&, or &_src/lookups_&); add a line for the new
-driver or lookup type and add it to the definition of OBJ.
-.next
-Edit &_OS/Makefile-Base_& adding a &_.o_& file for the predefined-macros, to the
-definition of OBJ_MACRO.  Add a set of line to do the compile also.
-.next
-Create &_newdriver.h_& and &_newdriver.c_& in the appropriate sub-directory of
-&_src_&.
-.next
-Edit &_scripts/MakeLinks_& and add commands to link the &_.h_& and &_.c_& files
-as for other drivers and lookups.
-.endlist
-
-Then all you need to do is write the code! A good way to start is to make a
-proforma by copying an existing module of the same type, globally changing all
-occurrences of the name, and cutting out most of the code. Note that any
-options you create must be listed in alphabetical order, because the tables are
-searched using a binary chop procedure.
-
-There is a &_README_& file in each of the sub-directories of &_src_& describing
-the interface that is expected.
-
-
-
-
-. ////////////////////////////////////////////////////////////////////////////
-. ////////////////////////////////////////////////////////////////////////////
-
-. /////////////////////////////////////////////////////////////////////////////
-. These lines are processing instructions for the Simple DocBook Processor that
-. Philip Hazel has developed as a less cumbersome way of making PostScript and
-. PDFs than using xmlto and fop. They will be ignored by all other XML
-. processors.
-. /////////////////////////////////////////////////////////////////////////////
-
-.literal xml
-<?sdop
-  format="newpage"
-  foot_right_recto="&chaptertitle;"
-  foot_right_verso="&chaptertitle;"
-?>
-.literal off
-
-.makeindex "Options index"   "option"
-.makeindex "Variables index" "variable"
-.makeindex "Concept index"   "concept"
-
-
-. /////////////////////////////////////////////////////////////////////////////
-. /////////////////////////////////////////////////////////////////////////////