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

Main changes with Postfix version 2.2
-------------------------------------

This is a summary of the changes. These and more are detailed in
the following sections of this document.

- TLS and IPv6 support are now built into Postfix, based on code
from third-party patches.

- Extended query interface for LDAP, MySQL and PostgreSQL with free
form SQL queries, and domain filters to reduce unnecessary lookups.

- SMTP client-side connection reuse. This can dramatically speed
up deliveries to high-volume destinations that have some servers
that respond, and some non-responding mail servers.

- By default, Postfix no longer rewrites message headers in mail
from remote clients. This includes masquerading, canonical mapping,
replacing "!" and "%" by "@", and appending the local domain to
incomplete addresses.  Thus, spam from poorly written software no
longer looks like it came from a local user.

- When your machine does not have its own domain name, Postfix can
now replace your "home network" email address by your ISP account
in outgoing SMTP mail, while leaving your email address unchanged
when sending mail to someone on the local machine.

- Compatibility workarounds: you can now selectively turn off ESMTP
features such as AUTH or STARTTLS in the Postfix SMTP client or
server, without having to "dumb down" other mail deliveries, and
without having to use transport maps for outgoing mail.

- Remote SMTP client resource control (the anvil server).  This
allows you to limit the number of connections, or the number of
MAIL FROM and RCPT TO commands that an SMTP client can send per
unit time.

- Support for CDB, SDBM and NIS+ databases is now built into Postfix
(but the CDB and SDBM libraries are not).

- New SMTP access control features, and more.

Major changes - critical
------------------------

BEFORE upgrading from an older release you MUST stop Postfix, unless
you're running a Postfix 2.2 snapshot release that already has
Postfix 2.2 IPV6 and TLS support.

AFTER upgrading from an older release DO NOT copy the old
master.cf/main.cf files over the new files.  Instead, you MUST let
the Postfix installation procedure update the existing configuration
files with new service entries.

[Incompat 20041118] The master-child protocol has changed.  The
Postfix master daemon will log warnings about partial status updates
if you don't stop and start Postfix.

[Incompat 20041023, 20041009] The queue manager to delivery agent
protocol has changed. Mail will remain queued if you do not restart
the queue manager.

[Incompat 20050111] The upgrade procedure adds the tlsmgr service
to the master.cf file. This service entry is not compatible with
the Postfix/TLS patch.

[Feature 20040919] The upgrade procedure adds the discard service
to the master.cf file.

[Feature 20040720] The upgrade procedure adds the scache (shared
connection cache) service to the master.cf file.

Major changes - IPv6 support
----------------------------

[Feature 20050111] Postfix version 2.2 IP version 6 support based
on the Postfix/IPv6 patch by Dean Strik and others.  IPv6 support
is always compiled into Postfix on systems that have Postfix
compatible IPv6 support. On other systems Postfix will simply use
IP version 4 just like it did before. See the IPV6_README document
for what systems are supported, and how to turn on IPv6 in main.cf.

[Incompat 20050111] Postfix version 2.2 IPv6 support differs from
the Postfix/IPv6 patch by Dean Strik in a few minor ways.

- Network protocol support including DNS lookup is selected with
the inet_protocols parameter instead of the inet_interfaces parameter.
This is needed so that Postfix will not attempt to deliver mail via
IPv6 when the system has no IPv6 connectivity.

- The lmtp_bind_address6 feature was omitted. The Postfix LMTP
client will be absorbed into the SMTP client, so there is no reason
to keep adding features to the LMTP client.

- The CIDR-based address matching code was rewritten.  The new
behavior is believed to be closer to expectation. The results may
be incompatible with that of the Postfix/IPv6 patch.

[Incompat 20050117] The Postfix SMTP server now requires that IPv6
addresses in SMTP commands are specified as [ipv6:ipv6address], as
described in RFC 2821.

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

[Feature 20041210] Postfix version 2.2 TLS support, based on the
Postfix/TLS patch by Lutz Jaenicke.  TLS support is not compiled
in by default.  For more information about Postfix 2.2 TLS support,
see the TLS_README document.

[Incompat 20041210] Postfix version 2.2 TLS support differs from
the Postfix/TLS patch by Lutz Jaenicke in a few minor ways.

- main.cf: Use btree instead of sdbm for TLS session cache databases.

  Session caches are now accessed only by the tlsmgr(8) process,
  so there are no concurrency issues. Although Postfix still has
  an SDBM client, the SDBM library (1000 lines of code) is no longer
  included with Postfix.

  TLS session caches can use any database that can store objects
  of several kbytes or more, and that implements the sequence
  operation. In most cases, btree databases should be adequate.

  NOTE: You cannot use dbm databases. TLS session objects are too
  large.

- master.cf: Specify unix instead of fifo for the tlsmgr service type.
  This change is automatically made by the Postfix upgrade procedure.

  The smtp(8) and smtpd(8) processes use a client-server protocol
  in order to access the tlsmgr(8)'s pseudo-random number generation
  (PRNG) pool, and in order to access the TLS session cache databases.
  Such a protocol cannot be run across fifos.

[Feature 20050209] The Postfix SMTP server policy delegation protocol
now supplies TLS client certificate information after successful
verification.  The new policy delegation protocol attribute names
are ccert_subject, ccert_issuer and ccert_fingerprint.

[Feature 20050208] New "check_ccert_maps maptype:mapname" feature
to enforce access control based on hexadecimal client certificate
fingerprints.

Major changes - SMTP client connection cache
--------------------------------------------

[Feature 20040720] SMTP client-side connection caching. Instead of
disconnecting immediately after a mail transaction, the Postfix
SMTP client can save the open connection to the scache(8) connection
cache daemon, so that any SMTP client process can reuse that session
for another mail transaction.  See the CONNECTION_CACHE_README
document for a description of configuration and implementation.

This feature introduces the scache (connection cache) server, which
is added to your master.cf file when you upgrade Postfix.

[Feature 20040729] Opportunistic SMTP connection caching. When a
destination has a high volume of mail in the active queue, SMTP
connection caching is enabled automatically.  This is controlled
with a new configuration parameter "smtp_connection_cache_on_demand"
(default:  yes).

[Feature 20040723] Per-destination SMTP connection caching. This
is enabled with the smtp_connection_cache_destinations parameter.
The parameter requires "bare" domain names or IP addresses without
"[]" or TCP port, to avoid a syntax conflict between host:port and
maptype:mapname entries.

[Feature 20040721] The scache(8) connection cache manager logs cache
hit and miss statistics every $connection_cache_status_update_time
seconds (default: 600s).  It reports the hit and miss rates for
lookups by domain, as well as for lookups by network address.

Major changes - address rewriting
---------------------------------

[Feature 20050206] Support for address rewriting in outgoing SMTP
mail (headers and envelopes). This is useful for sites that have a
fantasy Internet domain name such as localdomain.local.  Mail
addresses that use fantasy domain names are often rejected by mail
servers.

The smtp_generic_maps feature allows you to replace a local mail
address (user@localdomain.local) by a valid Internet address
(account@isp.example) when mail is sent across the Internet.  The
feature has no effect on mail that is sent between accounts on the
local machine. The syntax is described in generic(5) and a detailed
example is in the STANDARD_CONFIGURATION_README document, the section
titled "Postfix on hosts without a real Internet hostname".

[Feature 20041023] By default, Postfix no longer rewrites message
headers in mail from remote clients. This includes masquerading,
canonical mapping, replacing "!" and "%" by "@", and appending the
local domain to incomplete addresses.  Thus, spam from poorly written
software no longer looks like it came from a local user.

By default, Postfix rewrites message header addresses only when the
client IP address matches the local machine's interface addresses,
or when mail is submitted with the Postfix sendmail(1) command.

Postfix rewrites message headers in mail from other clients only
when the remote_header_rewrite_domain parameter specifies a domain
name (such as "domain.invalid"); this domain is appended to incomplete
addresses. Rewriting also includes masquerading, canonical mapping,
and replacing "!" and "%" by "@".

To get the behavior before Postfix 2.2 (always append Postfix's own
domain to incomplete addresses in message headers, always subject
message headers to canonical mapping, address masquerading, and
always replace "!" and "%" by "@") specify:

/etc/postfix/main.cf:
    local_header_rewrite_clients = static:all

If you must rewrite headers in mail from specific clients then you
can specify, for example,

/etc/postfix/main.cf:
    local_header_rewrite_clients = permit_mynetworks,
	permit_sasl_authenticated, permit_tls_clientcerts,
	check_address_map hash:/etc/postfix/pop-before-smtp

Postfix always appends local domain information to envelope addresses
(as opposed to header addresses), because an unqualified envelope
address is effectively local for the purpose of delivery, and for
the purpose of replying to it.

Full details are given in ADDRESS_REWRITING_README, and in the
postconf(5) manual. For best results, point your browser at the
ADDRESS_REWRITING_README.html file and navigate to the section
titled " To rewrite message headers or not, or to label as invalid".

[Incompat 20050212] When header address rewriting is enabled, Postfix
now updates a message header only when at least one address in that
header is modified.  Older Postfix versions first parse and then
un-parse a header so that there may be subtle changes in formatting,
such as the amount of whitespace between tokens.

[Incompat 20050227] Postfix no longer changes message header labels.
Thus, FROM: or CC: are no longer replaced by From: or Cc:.

[Feature 20040827] Finer control over canonical mapping with
canonical_classes, sender_canonical_classes and
recipient_canonical_classes.  These specify one or more of
envelope_sender, header_sender, envelope_recipient or header_recipient.
The default settings are backwards compatible.

Major changes - SMTP compatibility controls
-------------------------------------------

[Feature 20041218] Fine control for SMTP inter-operability problems,
by discarding keywords that are sent or received with the EHLO
handshake.  Typically one would discard "pipelining", "starttls",
or "auth" to work around systems with a broken implementation.
Specify a list of EHLO keywords with the smtp(d)_discard_ehlo_keywords
parameters, or specify one or more lookup tables, indexed by remote
network address, with the smtp(d)_discard_ehlo_keyword_address_maps
parameters.

Note: this feature only discards words from the EHLO conversation;
it does not turn off the actual features in the SMTP server.

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

[Feature 20050209] Extended LDAP, MySQL and PgSQL query interface
with free form SQL queries, the domain filter optimization that was
already available with LDAP and more. This code was worked on by
many people but Victor Duchovni took the lead. See the respective
{LDAP,MYSQL,PGSQL}_README and {ldap,mysql,pgsql}_table documents.

[Feature 20041210] You can now dump an entire database with the new
postmap/postalias "-s" option. This works only for database types
with Postfix sequence operator support: hash, btree, dbm, and sdbm.

[Feature 20041208] Support for CDB databases by Michael Tokarev.
This supports both Michael's tinycdb and Daniel Bernstein's cdb
implementations, but neither of the two implementations is bundled
with Postfix.

[Feature 20041023] The NIS+ client by Geoff Gibbs is now part of
the Postfix source tree. Details are given in the nisplus_table(5)
manual page.

[Feature 20040827] Easier use of the proxymap(8) service with the
virtual(8) delivery agent. The virtual(8) delivery agent will
silently open maps directly when those maps can't be proxied for
security reasons.  This means you can now specify "virtual_mailbox_maps
= proxy:mysql:whatever" without triggering a fatal error in the
virtual(8) delivery agent.

Major changes - remote SMTP client resource control
---------------------------------------------------

[Incompat 20041009] The smtpd_client_connection_limit_exceptions
parameter is renamed to smtpd_client_event_limit_exceptions. Besides
connections it now also applies to per-client message rate and
recipient rate limits.

[Feature 20041009] Per SMTP client message rate and recipient rate
limits. These limit the number of MAIL FROM or RCPT TO requests
regardless of whether or not Postfix would have accepted them
otherwise. The user interface (smtpd_client_message_rate_limit and
smtpd_client_recipient_rate_limit) is similar to that of the existing
per SMTP client connection rate limit, and the same warnings apply:
these features are to be used to stop abuse, and must not be used
to regulate legitimate mail.  More details can be found in the
postconf(5) manual.

Major changes - remote SMTP client access control
-------------------------------------------------

[Feature 20050209] The Postfix SMTP server policy delegation protocol
now supplies TLS client certificate information after successful
verification.  The new policy delegation protocol attribute names
are ccert_subject, ccert_issuer and ccert_fingerprint.

[Feature 20050208] New "check_ccert_maps maptype:mapname" feature
to enforce access control based on hexadecimal client certificate
fingerprints.

[Feature 20050203] New "permit_inet_interfaces" access restriction
to allow access from local IP addresses only.  This is used for the
default, purist, setting of local_header_rewrite_clients (rewrite
only headers in mail from this machine).

[Feature 20050203] New "sleep time-in-seconds" pseudo access
restriction to block zombie clients with reject_unauthorized_pipelining
before the Postfix SMTP server sends the SMTP greeting. See postconf(5)
for example. This feature is not available the stable Postfix 2.2
release, but it is documented here so that it will not get lost.

[Feature 20041118] New "smtpd_end_of_data_restrictions" feature
that is invoked after the client terminates the SMTP DATA command.
The syntax is the same as with "smtpd_data_restrictions".  In the
SMTPD policy delegation request, the message size is the actual
byte count of the message content, instead of the message size
announced by the client in the MAIL FROM command.

Major changes - SASL authentication
-----------------------------------

[Feature 20040827] Better SMTP client control over the use of SASL
mechanisms. New smtp_sasl_mechanism_filter mechanism to shorten the
list of SASL mechanisms from a remote server to just those that the
local SASL library can actually use.

Major changes - header/body patterns
------------------------------------

[Feature 20050205] REPLACE action in header_checks and body_checks,
to replace a message header or body line.  See header_checks(5) for
details.

Major changes - local delivery
------------------------------

[Feature 20040621] Control over the working directory when executing
an external command.  With the pipe(8) mailer, specify directory=pathname,
and with local(8) specify "command_execution_directory = expression"
where "expression" is subject to $home etc. macro expansion. The
result of macro expansion is restricted by the set of characters
specified with execution_directory_expansion_filter.

Major changes - mail delivery attributes
----------------------------------------

[Feature 20041218] More client attributes for delivery to command
with the local(8) and pipe(8) delivery agents: client_hostname,
client_address, client_protocol, client_helo, sasl_method, sasl_sender,
and sasl_username.  With local(8), attribute names must be specified
in upper case.

Major changes - package creation
--------------------------------

[Feature 20050203] To create a ready-to-install package for
distribution to other systems you can now use "make package" or
"make non-interactive-package", instead of invoking the internal
postfix-install script by hand. See the PACKAGE_README file for
details.

Major changes - performance
---------------------------

[Incompat 20050117] Only the deferred and defer queue directories
are now hashed by default, instead of eight queue directories.  This
may speed up Postfix boot time on low-traffic systems without
compromising performance under high load too much. Hashing must be
turned on for the defer and deferred queue directories, because
those directories contain lots of files when undeliverable mail is
backing up.

[Incompat 20040720] The default SMTP/LMTP timeouts for sending RSET
are reduced to 20s.

Major changes - miscellaneous
-----------------------------

[Feature 20050203] Safety: Postfix no longer tries to send mail to
the fallback_relay when the local machine is MX host for the mail
destination. See the postconf(5) description of the fallback_relay
feature for details.

[Incompat 20041023] Support for the non-standard Errors-To: return
addresses is now removed from Postfix.  It was already disabled by
default with Postfix version 2.1. Since Errors-To: is non-standard,
there was no guarantee that it would have the desired effect with
other MTAs.

[Feature 20040919] A new discard(8) mail delivery agent that makes
throwing away mail easier and more efficient. It's the Postfix
equivalent of /dev/null for mail deliveries. On the mail receiving
side, Postfix already has a /dev/null equivalent in the form of the
DISCARD action in access maps and header_body_checks.

[Feature 20040919] Access control for local mail submission, for
listing the queue, and for flushing the queue. These features are
controlled with authorized_submit_users, authorized_mailq_users,
and with authorized_flush_users, respectively. The last two controls
are always permitted for the super-user and for the mail system
owner.  More information is in the postconf(5) manual.

[Incompat 20040829] When no recipients are specified on the command
line or via the -t option, the Postfix sendmail command terminates
with status EX_USAGE and produces an error message instead of
accepting the mail first and bouncing it later. This gives more
direct feedback in case of a common client configuration error.