postfix/dist/RELEASE_NOTES-3.0

The stable Postfix release is called postfix-3.0.x where 3=major
release number, 0=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-3.1-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 2.10 or earlier, read RELEASE_NOTES-2.11
before proceeding.

Notes for distribution maintainers
----------------------------------

* New backwards-compatibility safety net.

With NEW Postfix installs, you MUST install a main.cf file with
the setting "compatibility_level = 2". See conf/main.cf for an
example.

With UPGRADES of existing Postfix systems, you MUST NOT change the
main.cf compatibility_level setting, nor add this setting if it
does not exist.

Several Postfix default settings have changed with Postfix 3.0.  To
avoid massive frustration with existing Postfix installations,
Postfix 3.0 comes with a safety net that forces Postfix to keep
running with backwards-compatible main.cf and master.cf default
settings. This safety net depends on the main.cf compatibility_level
setting (default: 0). Details are in COMPATIBILITY_README.

* New Postfix build system.

The Postfix build/install procedure has changed to support Postfix
dynamically-linked libraries and database plugins. These must not
be "shared" with non-Postfix programs, and therefore must not be
installed in a public directory.

To avoid massive frustration due to broken patches, PLEASE BUILD
POSTFIX FIRST WITHOUT APPLYING ANY PATCHES.  Follow the INSTALL
instructions (see "Building with Postfix dynamically-linked libraries
and database plugins"), and see how things work and what the
dynamically-linked libraries, database plugin, and configuration
files look like.  Then, go ahead and perform your platform-specific
customizations. The INSTALL section "Tips for distribution maintainers"
has further suggestions.

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

[Incompat 20140714] After upgrading Postfix, "postfix reload" (or
start/stop) is required. Several Postfix-internal protocols have
been extended to support SMTPUTF8. Failure to reload or restart
will result in mail staying queued, while Postfix daemons log
warning messages about unexpected attributes.

Major changes - default settings
--------------------------------

[Incompat 20141009] The default settings have changed for relay_domains
(new: empty, old: $mydestination) and mynetworks_style (new: host,
old: subnet).  However the backwards-compatibility safety net will
prevent these changes from taking effect, giving the system
administrator the option to make an old default setting permanent
in main.cf or to adopt the new default setting, before turning off
backwards compatibility. See COMPATIBILITY_README for details.

[Incompat 20141001] A new backwards-compatibility safety net forces
Postfix to run with backwards-compatible main.cf and master.cf
default settings after an upgrade to a newer but incompatible Postfix
version. See COMPATIBILITY_README for details.

While the backwards-compatible default settings are in effect,
Postfix logs what services or what email would be affected by the
incompatible change. Based on this the administrator can make some
backwards-compatibility settings permanent in main.cf or master.cf,
before turning off backwards compatibility.

See postconf.5.html#compatibility_level for details.

[Incompat 20141001] The default settings
have changed for append_dot_mydomain (new: no.  old: yes), master.cf
chroot (new: n, old: y), and smtputf8 (new: yes, old: no).

Major changes - access control
------------------------------

[Feature 20141119] Support for BCC actions in header/body_checks
and milter_header_checks.  There is no limit on the number of BCC
actions that may be specified, other than the implicit limit due
to finite storage. BCC support will not be implemented in Postfix
delivery agent header/body_checks.

It works in the same way as always_bcc and sender/recipient_bcc_maps:
there can be only one address per action, recipients are added with
the NOTIFY=NONE delivery status notification option, and duplicate
recipients are ignored (with the same delivery status notification
options).

[Incompat 20141009] The default settings have changed for relay_domains
(new: empty, old: $mydestination) and mynetworks_style (new: host,
old: subnet).  However the backwards-compatibility safety net will
prevent these changes from taking effect, giving the system
administrator the option to make an old default setting permanent
in main.cf or to adopt the new default setting, before turning off
backwards compatibility. See COMPATIBILITY_README for details.

[Feature 20140618] New INFO action in access(5) tables, for consistency
with header/body_checks.

[Feature 20140620] New check_xxx_a_access (for xxx in client,
reverse_client, helo, sender, recipient) implements access control
on all A and AAAA IP addresses for respectively the client hostname,
helo parameter, sender domain or recipient domain. This complements
the existing check_xxx_mx_access and check_xxx_ns_access features.

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

[Incompat 20141001] The default settings have changed for
append_dot_mydomain (new: no.  old: yes), master.cf chroot (new:
n, old: y), and smtputf8 (new: yes, old: no).

Major changes - address verification
------------------------------------

[Feature 20141227] The new smtp_address_verify_target parameter
(default: rcpt) specifies what protocol stage decides if a recipient
is valid. Specify "data" for servers that reject invalid recipients
in response to the DATA command.

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

[Feature 20140512] Support for Berkeley DB version 6.

[Feature 20140618] The "randmap" lookup table performs random
selection. This may be used to implement load balancing, for example:

/etc/postfix/transport:
    # Deliver my own domain as usual.
    example.com :
    .example.com :

/etc/postfix/main.cf:
    transport_maps =
        # Deliver my own domain as usual.
        hash:/etc/postfix/transport
        # Deliver other domains via randomly-selected relayhosts
        randmap:{smtp:smtp0.example.com, smtp:smtp1.example.com}

A variant of this can randomly select SMTP clients with different
smtp_bind_address settings.

To implement different weights, specify lookup results multiple
times. For example, to choose smtp:smtp1.example.com twice as often
as smtp:smtp0.example.com, specify smtp:smtp1.example.com twice.

A future version may support randmap:/path/to/file to load a list
of results from file.

[Feature 20140618] As the name suggests, the "pipemap" table
implements a pipeline of lookup tables. The name of the table
specifies the pipeline as a sequence of tables. For example, the
following prevents SMTP mail to system accounts that have "nologin"
as their login shell:

    /etc/postfix/main.cf:
        local_recipient_maps =
            pipemap:{unix:passwd.byname, pcre:/etc/postfix/no-nologin.pcre}
            alias_maps

    /etc/postfix/no-nologin.pcre:
        !/nologin/      whatever

Each "pipemap:" query is given to the first table. Each table
lookup result becomes the query for the next table in the pipeline,
and the last table produces the final result.  When any table lookup
produces no result, the entire pipeline produces no result.

A future version may support pipemap:/path/to/file to load a list
of lookup tables from file.

[Feature 20140924] Support for unionmap, with the same syntax as
pipemap.  This sends a query to all tables, and concatenates non-empty
results, separated by comma.

[Feature 20131121] The "static" lookup table now supports whitespace
when invoked as "static:{ text with whitespace }", so that it can
be used, for example, at the end of smtpd_mumble_restrictions as
"check_mumble_access static:{reject text...}".

[Feature 20141126] "inline:{key=value, { key = text with comma/space}}"
avoids the need to create a database for just a few entries.

Major changes - delivery status notifications
---------------------------------------------

[Feature 20140321] Delivery status filter support, to replace the
delivery status codes and explanatory text of successful or
unsuccessful deliveries by Postfix mail delivery agents.

This was originally implemented for sites that want to turn certain
soft delivery errors into hard delivery errors, but it can also be
used to censor out information from delivery confirmation reports.

This feature is implemented as a filter that replaces the three-number
enhanced status code and descriptive text in Postfix delivery agent
success, bounce, or defer messages. Note: this will not override
"soft_bounce=yes", and this will not change a successful delivery
status into an unsuccessful status or vice versa.

The first example turns specific soft TLS errors into hard
errors, by overriding the first number in the enhanced status code.

/etc/postfix/main.cf:
    smtp_delivery_status_filter = pcre:/etc/postfix/smtp_dsn_filter

/etc/postfix/smtp_dsn_filter:
    /^4(\.\d+\.\d+ TLS is required, but host \S+ refused to start TLS: .+)/ 5$1
    /^4(\.\d+\.\d+ TLS is required, but was not offered by host .+)/ 5$1

The second example removes the destination command name and file
name from local(8) successful delivery reports, so that they will
not be reported when a sender requests confirmation of delivery.

/etc/postfix/main.cf:
    local_delivery_status_filter = pcre:/etc/postfix/local_dsn_filter

/etc/postfix/local_dsn_filter:
    /^(2\S+ delivered to file).+/    $1
    /^(2\S+ delivered to command).+/ $1

This feature is supported in the lmtp(8), local(8), pipe(8), smtp(8)
and virtual(8) delivery agents. That is, all delivery agents that
actually deliver mail.  It will not be implemented in the error and
retry pseudo-delivery agents.

The new main.cf parameters and default values are:

    default_delivery_status_filter =
    lmtp_delivery_status_filter = $default_delivery_status_filter
    local_delivery_status_filter = $default_delivery_status_filter
    pipe_delivery_status_filter = $default_delivery_status_filter
    smtp_delivery_status_filter = $default_delivery_status_filter
    virtual_delivery_status_filter = $default_delivery_status_filter

See the postconf(5) manpage for more details.

[Incompat 20140618] The pipe(8) delivery agent will now log a limited
amount of command output upon successful delivery, and will report
that output in "SUCCESS" delivery status reports. This is another
good reason to disable inbound DSN requests at the Internet perimeter.

[Feature 20140907] With "confirm_delay_cleared = yes", Postfix
informs the sender when delayed mail leaves the queue (this is in
addition to the delay_warning_time feature that warns when mail is
still queued).  This feature is disabled by default, because it can
result in a sudden burst of notifications when the queue drains at
the end of a prolonged network outage.

Major changes - dns
-------------------

[Feature 20141128] Support for DNS server reply filters in the
Postfix SMTP/LMTP client and SMTP server. This helps to work around
mail delivery problems with sites that have incorrect DNS information.
Note: this has no effect on the implicit DNS lookups that are made
by nsswitch.conf or equivalent mechanisms.

This feature renders each lookup result as one line of text in
standard zone-file format as shown below. The class field is always
"IN", the preference field exists only for MX records, the names
of hosts, domains, etc. end in ".", and those names are in ASCII
form (xn--mumble form for internationalized domain names).

    name         ttl   class type preference value
    ---------------------------------------------------------
    postfix.org. 86400 IN    MX   10         mail.cloud9.net.

Typically, one would match this text with a regexp: or pcre: table.
When a match is found, the table lookup result specifies an action.
By default, the table query and the action name are case-insensitive.
Currently, only the IGNORE action is implemented.

For safety reasons, Postfix logs a warning or defers mail delivery
when a DNS reply filter removes all lookup results from a successful
query.

The Postfix SMTP/LMTP client uses the smtp_dns_reply_filter and
lmtp_dns_reply_filter features only for Postfix SMTP client lookups
of MX, A, and AAAAA records to locate a remote SMTP or LMTP server,
including lookups that implement the features reject_unverified_sender
and reject_unverified_recipient. The filters are not used for lookups
made through nsswitch.conf and similar mechanisms.

The Postfix SMTP server uses the smtpd_dns_reply_filter feature
only for Postfix SMTP server lookups of MX, A, AAAAA, and TXT records
to implement the features reject_unknown_helo_hostname,
reject_unknown_sender_domain, reject_unknown_recipient_domain,
reject_rbl_*, and reject_rhsbl_*. The filter is not used for lookups
made through nsswitch.conf and similar mechanisms, such as lookups
of the remote SMTP client name.

[Feature 20141126] Nullmx support (MX records with a null hostname).
This change affects error messages only.  The Postfix SMTP client
already bounced mail for such domains, and the Postfix SMTP server
already rejected such domains with reject_unknown_sender/recipient_domain.
This feature introduces a new SMTP server configuration parameter
nullmx_reject_code (default: 556).

Major changes - dynamic linking
-------------------------------

[Feature 20140530] Support to build Postfix with Postfix
dynamically-linked libraries, and with dynamically-loadable database
clients. These MUST NOT be used by non-Postfix programs. Postfix
dynamically-linked libraries introduce minor runtime overhead and
result in smaller Postfix executable files. Dynamically-loadable
database clients are useful when you distribute or install pre-compiled
packages.  Postfix 3.0 supports dynamic loading for CDB, LDAP, LMDB,
MYSQL, PCRE, PGSQL, SDBM, and SQLITE database clients.

This implementation is based on Debian code by LaMont Jones, initially
ported by Viktor Dukhovni. Currently, support exists for recent
versions of Linux, FreeBSD, MacOS X, and for the ancient Solaris 9.

To support Postfix dynamically-linked libraries and dynamically-loadable
database clients, the Postfix build procedure had to be changed
(specifically, the files makedefs and Makefile.in, and the files
postfix-install and post-install that install or update Postfix).

[Incompat 20140530] The Postfix 3.0 build procedure expects that
you specify database library dependencies with variables named
AUXLIBS_CDB, AUXLIBS_LDAP, etc.  With Postfix 3.0 and later, the
old AUXLIBS variable still supports building a statically-loaded
CDB etc.  database client, but only the new AUXLIBS_CDB etc. variables
support building a dynamically-loaded or statically-loaded CDB etc.
database client.  See CDB_README, LDAP_README, etc. for details.

Failure to follow this advice will defeat the purpose of dynamic
database client loading. Every Postfix executable file will have
database library dependencies. And that was exactly what dynamic
database client loading was meant to avoid.

Major changes - future proofing
-------------------------------

[Cleanup 20141224] The changes described here have no visible effect
on Postfix behavior, but they make Postfix code easier to maintain,
and therefore make new functionality easier to add.

* Compile-time argument typechecks of non-printf/scanf-like variadic
  function argument lists.

* Deprecating the use of "char *" for non-text purposes such as
  memory allocation and pointers to application context for call-back
  functions. This dates from long-past days before void * became
  universally available.

* Replace integer types for counters and sizes with size_t or ssize_t
  equivalents.  This eliminates some wasteful 64<->32bit conversions
  on 64-bit systems.

Major changes - installation pathnames
--------------------------------------

[Incompat 20140625] For compliance with file system policies, some
non-executable files have been moved from $daemon_directory to the
directory specified with the new meta_directory configuration
parameter which has the same default value as the config_directory
parameter. This change affects non-executable files that are shared
between multiple Postfix instances such as postfix-files, dynamicmaps.cf,
and multi-instance template files.

For backwards compatibility with Postfix 2.6 .. 2.11, specify
"meta_directory = $daemon_directory" in main.cf before installing
or upgrading Postfix, or specify "meta_directory = /path/name" on
the "make makefiles", "make install" or "make upgrade" command line.

Major changes - milter
----------------------

[Feature 20140928] Support for per-Milter settings that override
main.cf parameters.  For details see the section "Advanced policy
client configuration" in the SMTPD_POLICY_README document.

Here is an example that uses both old and new syntax:

    smtpd_milters = { inet:127.0.0.1:port1, default_action=accept, ... },
        inet:127.0.0.1:port2, ...

The supported attribute names are: command_timeout, connect_timeout,
content_timeout, default_action, and protocol. These have the same
names as the corresponding main.cf parameters, without the "milter_"
prefix.

The per-milter settings are specified as attribute=value pairs
separated by comma or space; specify { name = value } to allow
spaces around the "=" or within an attribute value.

[Feature 20141018] DMARC compatibility: when a Milter inserts a
header ABOVE Postfix's own Received: header, Postfix no longer
exposes its own Received: header to Milters (violating protocol)
and Postfix no longer hides the Milter-inserted header from Milters
(wtf).

Major changes - parameter syntax
--------------------------------

[Feature 20140921] In preparation for configurable mail headers and
logging, new main.cf support for if-then-else expressions:

    ${name?{text1}:{text2}}

and for logical expressions:

    ${{text1}=={text2}?{text3}:{text4}}
    ${{text1}!={text2}?{text3}:{text4}}

Whitespace before and after {text} is ignored. This can help to
make complex expressions more readable.  See the postconf(5) manpage
for further details.

[Feature 20140928] Support for whitespace in daemon command-line
arguments. For details, see the "Command name + arguments" section
in the master(5) manpage.  Example:

    smtpd -o { parameter = value containing whitespace } ...

The { ... } form is also available for non-option command-line
arguments in master.cf, for example:

    pipe ... argv=command { argument containing whitespace } ...

In both cases, whitespace immediately after "{" and before "}"
is ignored.

[Feature 20141005] Postfix import_environment and export_environment
now allow "{ name=value }" to protect whitespace in attribute values.

[Feature 20141006] The new message_drop_header parameter replaces
a hard-coded table that specifies what message headers the cleanup
daemon will remove.  The list of supported header names covers RFC
5321, 5322, MIME RFCs, and some historical names.

Major changes - pipe daemon
---------------------------

[Incompat 20140618] The pipe(8) delivery agent will now log a limited
amount of command output upon successful delivery, and will report
that output in "SUCCESS" delivery status reports. This is another
good reason to disable inbound DSN requests at the Internet perimeter.

Major changes - policy client
-----------------------------

[Feature 20140703] This release introduces three new configuration
parameters that control error recovery for failed SMTPD policy
requests.

  * smtpd_policy_service_default_action (default: 451 4.3.5 Server
    configuration problem): The default action when an SMTPD policy
    service request fails.

  * smtpd_policy_service_try_limit (default: 2): The maximal number
    of attempts to send an SMTPD policy service request before
    giving up. This must be a number greater than zero.

  * smtpd_policy_service_retry_delay (default: 1s): The delay between
    attempts to resend a failed SMTPD policy service request. This
    must be a number greater than zero.

See postconf(5) for details and limitations.

[Feature 20140928] Support for per-policy service settings that
override main.cf parameters.  For details see the section "Different
settings for different Milter applications" in the MILTER_README
document.

Here is an example that uses both old and new syntax:

smtpd_recipient_restrictions = ...
    check_policy_service { inet:127.0.0.1:port3, default_action=DUNNO }
    check_policy_service inet:127.0.0.1:port4
    ...

The per-policy service settings are specified as attribute=value pairs
separated by comma or space; specify { name = value } to allow
spaces around the "=" or within an attribute value.

The supported attribute names are: default_action, max_idle, max_ttl,
request_limit, retry_delay, timeout, try_limit. These have the same
names as the corresponding main.cf parameters, without the
"smtpd_policy_service_" prefix.

[Feature 20140505] A client port attribute was added to the policy
delegation protocol.

[Feature 20140630] New smtpd_policy_service_request_limit feature to
limit the number of requests per Postfix SMTP server policy connection.
This is a workaround to avoid error-recovery delays with policy
servers that cannot maintain a persistent connection.

Major changes - position-independent executables
------------------------------------------------

[Feature 20150205] Preliminary support for building position-independent
executables (PIE), tested on Fedora Core 20, Ubuntu 14.04, FreeBSD
9 and 10, and NetBSD 6. Specify:

$ make makefiles pie=yes ...other arguments...

On some systems, PIE is used by the ASLR exploit mitigation technique
(ASLR = Address-Space Layout Randomization). Whether specifying
"pie=yes" has any effect at all depends on the compiler.  Reportedly,
some compilers always produce PIE executables.

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

[Feature 20140501] Configurable time limit (postscreen_dnsbl_timeout)
for DNSBL or DNSWL lookups. This is separate from the timeouts in
the dnsblog(8) daemon which are controlled by system resolver(3)
routines.

Major changes - session fingerprint
-----------------------------------

[Feature 20140801] The Postfix SMTP server now logs at the end of
a session how many times an SMTP command was successfully invoked,
followed by the total number of invocations if some invocations
were unsuccessful.

This logging will enough to diagnose many problems without using
verbose logging or network sniffer.

    Normal session, no TLS:
        disconnect from name[addr] ehlo=1 mail=1 rcpt=1 data=1 quit=1

    Normal session. with TLS:
        disconnect from name[addr] ehlo=2 starttls=1 mail=1 rcpt=1 data=1 quit=1

    All recipients rejected, no ESMTP command pipelining:
        disconnect from name[addr] ehlo=1 mail=1 rcpt=0/1 quit=1

    All recipients rejected, with ESMTP command pipelining:
        disconnect from name[addr] ehlo=1 mail=1 rcpt=0/1 data=0/1 rset=1 quit=1

    Password guessing bot, hangs up without QUIT:
        disconnect from name[addr] ehlo=1 auth=0/1

    Mis-configured client trying to use TLS wrappermode on port 587:
        disconnect from name[addr] unknown=0/1

Logfile analyzers can trigger on the presence of "/". It indicates
that Postfix rejected at least one command.

[Feature 20150118] As a late addition, the SMTP server now also
logs the total number of commands (as "commands=x/y") even when the
client did not send any commands. This helps logfile analyzers to
recognize sessions without commands.

Major changes - smtp client
---------------------------

[Feature 20141227] The new smtp_address_verify_target parameter
(default: rcpt) determines what protocol stage decides if a recipient
is valid. Specify "data" for servers that reject recipients after
the DATA command.

Major changes - smtputf8
------------------------

[Incompat 20141001] The default settings have changed for
append_dot_mydomain (new: no, old: yes), master.cf chroot (new:
n, old: y), and smtputf8 (new: yes, old: no).

[Incompat 20140714] After upgrading Postfix, "postfix reload" (or
start/stop) is required. Several Postfix-internal protocols have
been extended to support SMTPUTF8. Failure to reload or restart
will result in mail staying queued, while Postfix daemons log
warning messages about unexpected attributes.

[Feature 20140715] Support for Email Address Internationalization
(EAI) as defined in RFC 6531..6533. This supports UTF-8 in SMTP/LMTP
sender addresses, recipient addresses, and message header values.
The implementation is based on initial work by Arnt Gulbrandsen
that was funded by CNNIC.

See SMTPUTF8_README for a description of Postfix SMTPUTF8 support.

[Feature 20150112] UTF-8 Casefolding support for Postfix lookup
tables and matchlists (mydestination, relay_domains, etc.).  This
is enabled only with "smtpuf8 = yes".

[Feature 20150112] With smtputf8_enable=yes, SMTP commands with
UTF-8 syntax errors are rejected, table lookup results with invalid
UTF-8 syntax are handled as configuration errors, and UTF-8 syntax
errors in policy server replies result in execution of the policy
server's default action.

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

(see "Major changes - delivery status notifications" above for
turning 4XX soft errors into 5XX bounces when a remote SMTP server
does not offer STARTTLS support).

[Feature 20140209] the Postfix SMTP client now also falls back to
plaintext when TLS fails AFTER the TLS protocol handshake.

[Feature 20140218] The Postfix SMTP client now requires that a queue
file is older than $minimal_backoff_time, before falling back from
failed TLS to plaintext (both during or after the TLS handshake).

[Feature 20141021] Per IETF TLS WG consensus, the tls_session_ticket_cipher
default setting was changed from aes-128-cbc to aes-256-cbc.

[Feature 20150116] TLS wrappermode support in the Postfix smtp(8)
client (new smtp_tls_wrappermode parameter) and in posttls-finger(1)
(new -w option). There still is life in that deprecated protocol,
and people should not have to jump hoops with stunnel.