Basic documentation for cutthrough.

3 files changed, 54 insertions, 0 deletions

diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt
index 0ea36adc2..02aff0662 100644
--- a/doc/doc-docbook/spec.xfpt
+++ b/doc/doc-docbook/spec.xfpt
@@ -26906,6 +26906,27 @@ is what is wanted for subsequent tests.
 
 
 .new
+.vitem &*control&~=&~cutthrough_delivery*&
+.cindex "&ACL;" "cutthrough routing"
+This option requests delivery be attempted while the item is being received.
+It is usable in the RCPT ACL and valid only for single-recipient mails forwarded
+from one SMTP connection to another.  If a recipient-verify callout connection is
+requested in the same ACL it is held open and used for the data, otherwise one is made
+after the ACL completes.
+
+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 there is a temporary error the item is queued for later delivery in the
+usual fashion. If the item is successfully delivered in cutthrough mode the log line
+is tagged with ">>" rather than "=>" and appears before the acceptance "<="
+line.
+
+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.
+.wen
+
+
+.new
 .vitem &*control&~=&~dscp/*&<&'value'&>
 .cindex "&ACL;" "setting DSCP value"
 .cindex "DSCP" "inbound"
@@ -31632,6 +31653,8 @@ 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
diff --git a/doc/doc-txt/ChangeLog b/doc/doc-txt/ChangeLog
index ecf3985a6..02f526756 100644
--- a/doc/doc-txt/ChangeLog
+++ b/doc/doc-txt/ChangeLog
@@ -33,6 +33,8 @@ PP/07 Handle "exim -L <tag>" to indicate to use syslog with tag as the process
 
 TL/01 Bugzilla 1258 - Refactor MAIL FROM optional args processing.
 
+JH/01 Bugzilla 1201 & 304 - New cutthrough-delivery feature, with TLS support.
+
 Exim version 4.80
 -----------------
 
diff --git a/doc/doc-txt/NewStuff b/doc/doc-txt/NewStuff
index 7efbe6ef4..aae58c631 100644
--- a/doc/doc-txt/NewStuff
+++ b/doc/doc-txt/NewStuff
@@ -55,6 +55,35 @@ Version 4.81
     process name.  A few other flags used by Sendmail are now accepted and
     ignored.
 
+ 7. New cutthrough routing feature.  Requested by a "control = cutthrough_delivery"
+    ACL modifier; works for single-recipient mails which are recieved on and
+    deliverable via SMTP.  Using the connection made for a recipient verify,
+    if requested before the verify, or a new one made for the purpose while
+    the inbound connection is still active.  The bulk of the mail item is copied
+    direct from the inbound socket to the outbound (as well as the spool file).
+    When the source notifies the end of data, the data acceptance by the destination
+    is negociated before the acceptance is sent to the source.  If the destination
+    does not accept the mail item, for example due to content-scanning, the item
+    is not accepted from the source and therefore there is no need to generate
+    a bounce mail.  This is of benefit when providing a secondary-MX service.
+    The downside is that delays are under the control of the ultimate destination
+    system not your own.
+
+    The Recieved-by: header on items delivered by cutthrough is generated
+    early in of reception rather than at the end; this will affect any timestamp
+    included.  The log line showing delivery is recorded before that showing
+    reception; it uses a new ">>" tag instead of "=>".
+    
+    To support the feature, verify-callout connections can now use ESMTP and TLS.
+    The usual smtp transport options are honoured, plus a (new, default everything)
+    hosts_verify_avoid_tls.
+
+    New variable families named tls_in_cipher, tls_out_cipher etc. are introduced
+    for specific access to the information for each connection.  The old names
+    are present for now but deprecated.
+
+    Not yet supported: IGNOREQUOTA, SIZE, PIPELINING, AUTH.
+
 
 Version 4.80
 ------------