The stable Postfix release is called postfix-2.10.x where 2=major
release number, 10=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-2.11-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 2.8 or earlier, read RELEASE_NOTES-2.9
before proceeding.

Major changes - laptop-friendliness
-----------------------------------

[Incompat 20120924] Postfix no longer uses FIFOs to emulate UNIX-domain
sockets on Solaris 9 (Vintage 2002!) and later. If you install
Postfix for the first time on an older Solaris system, edit the
master.cf file and replace "unix" with "fifo" for the pickup and
qmgr services.

[Feature 20120924] the default master.cf file now uses "unix" instead
of "fifo" for the pickup and qmgr services. This avoids periodic
disk drive spin-up.

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

[Feature 20120303] [Feature 20120303] New control for "permit"
logging in smtpd_mumble_restrictions (by default, the SMTP server
logs "reject" actions but not "permit" actions).  Specify
"smtpd_log_access_permit_actions = static:all" to log all "permit"-style
actions, or specify a list of explicit action names.  More details
are in the postconf(5) manpage.  

Major changes - postconf
------------------------

[Incompat 20121224] The postconf command produces more warnings:

- An attempt to modify a read-only parameter (process_name, process_id)
  in main.cf or master.cf.

- An undefined $name in a parameter value in main.cf or master.cf
  (except for backwards-compatibility parameters such as $virtual_maps).

[Feature 20121224] The postconf command has been updated to make
trouble-shooting (and support) easier. In summary, use "postconf
-Mxf" and "postconf -nxf" to review master.cf and main.cf parameter
settings with expanded parameter values.

- "postconf -x" now expands $name in main.cf and master.cf parameter
  values.

- postconf warns about attempts to modify a read-only parameter
  (process_name, process_id) in main.cf or master.cf.

- postconf warns about an undefined $name in a parameter value in
  main.cf or master.cf (except for backwards-compatibility parameters
  such as $virtual_maps).

[Feature 20121227]

- "postconf -o name=value" overrides main.cf parameter settings.
  This can be used, for example, to examine stress-dependent settings
  with "postconf -x -o stress=yes".

Major changes - postscreen
--------------------------

[Incompat 20121123] The postscreen deep protocol tests now log the
last command before a protocol error ("UNIMPLEMENTED" when the last
command is not implemented, "CONNECT" when there was no prior
command). The changed logfile messages are:

NON-SMTP COMMAND from [address]:port after command: text
BARE NEWLINE from [address]:port after command
COMMAND TIME LIMIT from [address]:port after command
COMMAND COUNT LIMIT from [address]:port after command
COMMAND LENGTH LIMIT from [address]:port after command

Major changes - load-balancer support
-------------------------------------

[Incompat 20120625] The postscreen(8)-to-smtpd(8) protocol has
changed.  To avoid "cannot receive connection attributes" warnings
and dropped connections, execute the command "postfix reload". No
mail will be lost as long as the remote SMTP client tries again
later.

[Feature 20120625] Support for upstream proxy agent in the postscreen(8)
and smtpd(8) daemons.  To enable the haproxy protocol, specify one
of the following:

    postscreen_upstream_proxy_protocol = haproxy
    smtpd_upstream_proxy_protocol = haproxy

Note 1: smtpd_upstream_proxy_protocol can't be used in smtpd processes
that are behind postscreen. Configure postscreen_upstream_proxy_protocol
instead.

Note 2: To use the nginx proxy with smtpd(8), enable the XCLIENT
protocol with smtpd_authorized_xclient_hosts. This supports SASL
authentication in the proxy agent (Postfix 2.9 and later).

Major changes - relay safety
----------------------------

[Incompat 20130613] New smtpd_relay_restrictions parameter built-in
default settings:

    smtpd_relay_restrictions = 
	permit_mynetworks 
	permit_sasl_authenticated 
	defer_unauth_destination

This safety net prevents open relay problems due to mistakes
with spam filter rules in smtpd_recipient_restrictions.

If your site has a complex mail relay policy configured under
smtpd_recipient_restrictions, this safety net may defer mail that
Postfix should accept.

To fix this safety net, take one of the following actions:

- Set smtpd_relay_restrictions empty, and keep using the existing
  mail relay authorization policy in smtpd_recipient_restrictions.

- Copy the existing mail relay authorization policy from
  smtpd_recipient_restrictions to smtpd_relay_restrictions.

There is no need to change the value of smtpd_recipient_restrictions.

[Feature 20130613] This version introduces the smtpd_relay_restrictions
feature for mail relay control. The new built-in default settings
are:

    smtpd_relay_restrictions = 
	permit_mynetworks 
 	permit_sasl_authenticated
	defer_unauth_destination

    smtpd_recipient_restrictions =
	( optional spam blocking rules would go here )

For comparison, this is the Postfix before 2.10 default:

    smtpd_recipient_restrictions =
	permit_mynetworks 
	reject_unauth_destination
	( optional spam blocking rules would go here )

With Postfix versions before 2.10, the mail relay policy and spam
blocking policy were combined under smtpd_recipient_restrictions,
resulting in error-prone configuration.

As of Postfix 2.10, the mail relay policy is preferably implemented
with smtpd_relay_restrictions, so that a permissive spam blocking
policy under smtpd_recipient_restrictions will not unexpectedly
result in a permissive mail relay policy.

As of Postfix 2.10.0 the smtpd_relay_restrictions parameter built-in
default settings are:

    smtpd_relay_restrictions =
        permit_mynetworks
        permit_sasl_authenticated
        defer_unauth_destination

If your site has a complex mail relay policy configured under
smtpd_recipient_restrictions, this safety net may defer mail that
Postfix should accept.

To migrate from an earlier Postfix release with the least amount
of pain:

- Set smtpd_relay_restrictions empty, and keep using the existing
  mail relay authorization policy in smtpd_recipient_restrictions.

- There is no need to change the value of smtpd_recipient_restrictions.

To take advantage of the new smtpd_relay_restrictions feature:

- Copy the existing mail relay authorization policy from
  smtpd_recipient_restrictions to smtpd_relay_restrictions.

- There is no need to change the value of smtpd_recipient_restrictions.

Major changes - start-up
------------------------

[Feature 20120306] New master "-w" option, to wait for master daemon
process initialization to complete. This feature returns an error
exit status if master daemon initialization fails, or if it does
not complete in a reasonable amount of time. The exit status is
used by "postfix start" to provide more accurate information to
system start-up scripts.

Major changes - tls
-------------------

[Incompat 20130203] Thanks to OpenSSL documentation, the Postfix
2.9.0..2.9.5 SMTP client and server server used an incorrect procedure
to compute TLS certificate PUBLIC-KEY fingerprints (these may be
used in the check_ccert_access and in smtp_tls_policy_maps features).
Support for certificate PUBLIC-KEY finger prints was introduced
with Postfix 2.9; there is no known problem with the certificate
fingerprint algorithms available since Postfix 2.2.

Certificate PUBLIC-KEY finger prints may be used in the Postfix
SMTP server (with "check_ccert_access") and in the Postfix SMTP
client (with the "fingerprint" security level).  

Specify "tls_legacy_public_key_fingerprints = yes" temporarily,
pending a migration from configuration files with incorrect Postfix
2.9.0..2.9.5 certificate PUBLIC-KEY finger prints, to the correct
fingerprints used by Postfix 2.9.6 and later.

To compute the correct PUBLIC-KEY finger prints:

# OpenSSL 1.0 with all certificates and SHA-1 fingerprints.
$ openssl x509 -in cert.pem -noout -pubkey | \
    openssl pkey -pubin -outform DER | \
    openssl dgst -sha1 -c

# OpenSSL 0.9.8 with RSA certificates and MD5 fingerprints.
$ openssl x509 -in cert.pem -noout -pubkey | \
    openssl rsa -pubin -outform DER | \
    openssl dgst -md5 -c

[Feature 20120422] This release adds support to turn off the TLSv1.1
and TLSv1.2 protocols.  Introduced with OpenSSL version 1.0.1, these
are known to cause inter-operability problems with for example
hotmail.

The radical workaround is to temporarily turn off problematic
protocols globally:

/etc/postfix/main.cf:
    smtp_tls_protocols = !SSLv2, !TLSv1.1, !TLSv1.2
    smtp_tls_mandatory_protocols = !SSLv2, !TLSv1.1, !TLSv1.2

    smtpd_tls_protocols = !SSLv2, !TLSv1.1, !TLSv1.2
    smtpd_tls_mandatory_protocols = !SSLv2, !TLSv1.1, !TLSv1.2

However, it may be better to temporarily turn off problematic
protocols for broken sites only:

/etc/postfix/main.cf:
    smtp_tls_policy_maps = hash:/etc/postfix/tls_policy

/etc/postfix/tls_policy:
    example.com         may protocols=!SSLv2:!TLSv1.1:!TLSv1.2

Important:

- Note the use of ":" instead of comma or space. Also, note that
  there is NO space around the "=" in "protocols=".

- The smtp_tls_policy_maps lookup key must match the "next-hop"
  destination that is given to the Postfix SMTP client. If you
  override the next-hop destination with transport_maps, relayhost,
  sender_dependent_relayhost_maps, or otherwise, you need to specify
  the same destination for the smtp_tls_policy_maps lookup key.