This is the Postfix 3.8 stable release.

The stable Postfix release is called postfix-3.8.x where 3=major
release number, 8=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-3.9-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 3.6 or earlier, please read RELEASE_NOTES-3.7
before proceeding.

Dual license
------------

As of Postfix 3.2.5 this software is distributed with a dual license:
in addition to the historical IBM Public License (IPL) 1.0, it is
now also distributed with the more recent Eclipse Public License
(EPL) 2.0. Recipients can choose to take the software under the
license of their choice. Those who are more comfortable with the
IPL can continue with that license.

Major changes - documentation and code cleanup
----------------------------------------------

There are numerous small fixes to Postfix documentation, and small
code-health changes that should not affect documented behavior but
may improve Postfix behavior for malformed input, or that make
Postfix easier to maintain. See the HISTORY file for details.

Major changes - SRV support
---------------------------

[Feature 20230214] Support to look up DNS SRV records in the Postfix
SMTP/LMTP client, Based on code by Tomas Korbar (Red Hat).

For example, with "use_srv_lookup = submission" and "relayhost =
example.com:submission", the Postfix SMTP client will look up DNS
SRV records for _submission._tcp.example.com, and will relay email
through the hosts and ports that are specified with those records.

See https://www.postfix.org/postconf.5.html#use_srv_lookup for more
details, including how to selectively use SRV in a configuration
that connects to multiple ISP accounts.

SRV support may also be useful inside a cloud-based infrastructure
when Postfix needs to deliver mail to services that run on a
dynamically-allocated port.

Major changes - TLS support
---------------------------

[Incompat 20230304] This introduces the following changes:

- Postfix treats the "export" and "low" cipher grade settings as
  "medium". The  "export" and "low" grades are no longer supported
  in OpenSSL 1.1.1, the minimum version that Postfix requires.

- Postfix default settings now exclude the following deprecated or
  unused ciphers (SEED, IDEA, 3DES, RC2, RC4, RC5), digest (MD5),
  key exchange algorithms (DH, ECDH), and public key algorithm
  (DSS).

[Feature 20230108] New configuration parameter tls_ffdhe_auto_groups
for finite-field Diffie-Hellman ephemeral (FFDHE) support in TLS
1.3 with OpenSSL 3.0.

Major changes - attack resistance
---------------------------------

[Feature 20240312] the Postfix SMTP server can now aggregate
smtpd_client_*_rate and smtpd_client_*_count statistics by network
block, as specified with smtpd_client_ipv4_prefix_length (default
32, no aggregation) and smtpd_client_ipv6_prefix_length (default
84, aggregation by /84 network blocks). The latter raises the bar
for a memory exhaustion attack.

[Feature 20221023] Unconditionally disable a CPU resource attack
requesting TLS renegotiation. There's no good reason to support
this in the middle of an SMTP connection.

Major changes - bit rot
-----------------------

[Incompat 20221228] Postfix documentation and code have been converted
to use "grep -E" and "grep -F" instead of the historical forms
"egrep" and "fgrep". To build Postfix on a system that supports
only the historical forms, run the script auxiliary/fix-grep/fix-grep.sh
to revert this change.

Major changes - configuration checks
------------------------------------

[Feature 20240406] The postconf command now warns for #comment in
or after a Postfix parameter value. Postfix programs do not support
#comment after other text, and treat that as input.

Major changes - database support
--------------------------------

[Incompat 20220509] The PostgreSQL client encoding is now configurable
with the "encoding" Postfix configuration file attribute. The default
is "UTF8". Previously the encoding was hard-coded as "LATIN1".

Major changes - logging
-----------------------

[Incompat 20230308] The postfix(1) and postlog(1) commands now
produce stderr logging even when stderr is not connected to a
terminal. This eliminates an inconsistency, and makes these programs
easier to use in some automated procedures. The canonical example
is to capture output from "postmulti -p status" to figure out which
instances are or are not running.

Major changes - source code organization
----------------------------------------

[Incompat 20220507] Most global/mkmap*.[hc] files are moved to the
util directory; only global/mkmap_proxy.* remains. The old file
organization was designed before support for dynamically-loadable
databases was added, and that code suffered from complexity.

