The stable Postfix release is called postfix-2.5.x where 2=major
release number, 5=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-2.6-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.

Incompatibility with Postfix 2.4 and earlier
============================================

If you upgrade from Postfix 2.4 or earlier, read RELEASE_NOTES-2.5
before proceeding.

Incompatibility with snapshot 20080629
======================================

When TLS support is not compiled in, the Postfix SMTP server no
longer ignores the "smtpd_tls_auth_only = yes" parameter setting.
Earlier Postfix SMTP server versions would announce SASL support,
and would accept SASL login or sender information.

Major changes with snapshot 20080629
====================================

The Postfix SMTP server's SASL authentication was re-structured.
With "smtpd_tls_auth_only = yes", SASL support is now activated
only after a successful TLS handshake. Earlier Postfix SMTP server
versions could complain about unavailable SASL mechanisms during
the plaintext phase of the SMTP protocol.

Incompatibility with snapshot 20080510
======================================

In the policy delegation protocol, certificate common name attributes
are now xtext encoded UTF-8. The xtext decoded attributes may contain
any UTF-8 value except non-printable ASCII characters.

Incompatibility with snapshot 20080428
======================================

Postfix SMTP server replies for address verification have changed.
unverified_recipient_reject_code and unverified_sender_reject_code
now handle "5XX" rejects only. The "4XX" rejects are now controlled
with unverified_sender_defer_code and unverified_recipient_defer_code.

Major changes with snapshot 20080428
====================================

Finer control over the way that Postfix reports address verification
failures are reported to remote SMTP clients.

- unverified_sender/recipient_defer_code: the numerical Postfix
  SMTP server reply code when address verification failed due
  to some temporary error.

- unverified_sender/recipient_reject_reason: fixed text that Postfix
  will send to the remote SMTP client, instead of sending actual
  address verification details.

Incompatible changes with snapshot 20080207
===========================================

According to discussions on the mailing list, too many people are
breaking newly installed Postfix by overwriting the new /etc/postfix
files with versions from an older release, and end up with a broken
configuration that cannot repair itself. For this reason, postfix-script,
postfix-files and post-install are moved away from /etc/postfix to
$daemon_directory.