The stable Postfix release is called postfix-2.3.x where 2=major
release number, 3=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-2.4-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 2.2 and earlier
============================================

If you upgrade from Postfix 2.2 or earlier, read RELEASE_NOTES-2.3
before proceeding.

Incompatible changes with Postfix snapshot 20061209
===================================================

The Postfix installation procedure no longer updates main.cf with
"unknown_local_recipient_reject_code = 450". Four years after the
introduction of mandatory recipient validation, this transitional
tool is no longer neeed.

After upgrading Postfix you MUST execute "postfix reload", otherwise
the queue manager may log a warnings with:

    warning: connect to transport retry: Connection refused

The upgrade procedure adds a new "retry" service to the master.cf
file.  If you make the mistake of copying old Postfix configuration
files over the new files, the queue manager may log warnings with:

    warning: connect to transport retry: Connection refused

To fix your master.cf file, use "postfix upgrade-configuration"
followed by "postfix reload".

Small changes were made to the default bounce message templates,
to prevent HTML-aware software from hiding or removing the text
"<postmaster>", and producing misleading text.

Major changes with Postfix snapshot 20061209
============================================

Better interoperability with non-conforming SMTP servers that reply
and disconnect before Postfix has sent the complete message content.

Improved worst-case (old and new) queue manager performance when
deferring or bouncing large amounts of mail. Instead of talking to
the bounce or defer service synchronously, this work is now done
in the background by the error or retry service.

Improved worst-case (new) queue manager performance when delivering
multi-recipient mail. The queue manager now proactively reads
recipients from the queue file, instead of waiting for the slowest
deliveries to complete before reading in new recipients.  This
introduces two parameters: default_recipient_refill_limit (how many
recipient slots to refill at a time) and default_recipient_refill_delay
(how long to wait between refill operations). These two parameters
act as defaults for optional per-transport settings.

Incompatible changes with Postfix snapshot 20061006
===================================================

The format of SMTP server TLS session cache lookup keys has changed.
The lookup key now includes the master.cf service name.

Major changes with Postfix snapshot 20061006
============================================

Individual CISCO PIX bug workarounds are now on/off configurable.
This introduces new parameters: smtp_pix_workarounds (default:
disable_esmtp, delay_dotcrlf) and smtp_pix_workaround_maps (workarounds
indexed by server IP address).  The default settings are backwards
compatible.

Incompatible changes with Postfix snapshot 20060806
===================================================

Postfix no longer announces its name in delivery status notifications.
Users believe that Wietse provides a free help desk service that
solves all their email problems.
