The stable Postfix release is called postfix-2.6.x where 2=major
release number, 6=minor release number, x=patchlevel.  The stable
release never changes except for patches that address bugs or
emergencies. Patches change the patchlevel and the release date.

New features are developed in snapshot releases. These are called
postfix-2.7-yyyymmdd where yyyymmdd is the release date (yyyy=year,
mm=month, dd=day).  Patches are never issued for snapshot releases;
instead, a new snapshot is released.

The mail_release_date configuration parameter (format: yyyymmdd)
specifies the release date of a stable release or snapshot release.

If you upgrade from Postfix 2.5 or earlier, read RELEASE_NOTES-2.6
before proceeding.

Incompatibility with snapshot 20090606
======================================

The "postmulti -e destroy" command no longer attempts to remove
files that are created AFTER "postmulti -e create".  It still works
as expected immediately after creating an instance by mistake.
Trying to automatically remove other files is too risky because
Postfix-owned directories are by design not trusted.

Major changes with snapshot 20090606
====================================

Support for header checks on Milter-generated message headers.  This
can be used, for example, to control mail flow with Milter-generated
headers with indicators for badness or goodness. For details, see
the postconf(5) section for "milter_header_checks". Currently, all
header_checks features are implemented except PREPEND.