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+Preamble
+========
+
+Normally The Exim Maintainers ensure that a configuration which works
+with version N will work with version N+1, within a major version number
+(eg, 4).
+
+Occasionally this will not be the case; usually, those changes will be
+at the end of a long notice period where admins have been encouraged to
+move away and even then, we are hesitant to fully break things without
+strong cause to move away.
+
+This does not apply to "experimental" features, which can be withdrawn
+or changed with little notice, although we still endeavour to limit
+that.  We may choose to note those changes here too.
+
+The most likely cause of a backwards-incompatible change is a security
+improvement, where the benefits for everyone strongly outweigh the needs
+of the few.
+
+
+Changes
+=======
+
+Exim version 4.73
+-----------------
+
+ * The Exim run-time user can no longer be root; this was always
+   strongly discouraged, but is now prohibited both at build and
+   run-time.  If you need Exim to run routinely as root, you'll need to
+   patch the source and accept the risk.  Here be dragons.
+
+ * Exim will no longer accept a configuration file owned by the Exim
+   run-time user, unless that account is explicitly the value in
+   CONFIGURE_OWNER, which we discourage.  Exim now checks to ensure that
+   files are not writable by other accounts.
+
+ * ALT_CONFIG_ROOT_ONLY is no longer optional and is forced on; the Exim
+   user can no longer use -C/-D and retain privilege.
+
+ * The system_filter_user option now defaults to the Exim run-time user,
+   rather than root.  You can still set it explicitly to root and this
+   can be done with prior versions too, letting you roll versions
+   without needing to change this configuration option.
+