The stable Postfix release is called postfix-2.6.x where 2=major release number, 6=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-2.7-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 2.4 or earlier, read RELEASE_NOTES-2.5 before proceeding. Major changes - multi-instance support -------------------------------------- [Feature 20090121] Support for managing multiple Postfix instances. This can automatically apply your "postfix start" etc. command to multiple Postfix instances, including upgrades to new Postfix versions. Multi-instance support allows you to do the following and more: - Simplify post-queue content filter configuration by using separate Postfix instances before and after the filter. This simplifies trouble shooting and performance tuning. - Implement per-user content filters (or no filter) via transport map lookups instead of content_filter settings. Mail for some users can be sent directly from the before-filter instance to the after-filter instance. - Test new configuration settings (on a different server IP address or TCP port) without disturbing production instances. - Each additional Postfix instance uses a few files and directories, plus memory for an extra master daemon and queue manager. The pickup daemon is needed only if you use local submission or "postsuper -r". Best of all, nothing changes when you use only one Postfix instance. The MULTI_INSTANCE_README file presents an introduction to multi-instance management. Multi-instance support is based on an API that is described in the postfix-wrapper(5) manual page. Major changes - milter support ------------------------------ [Feature 20090428] The following improvements have been made to the Milter implementation: - Improved compatibility of the {mail_addr} and {rcpt_addr} macros. - Support for the {mail_host}, {mail_mailer}, {rcpt_host} and {rcpt_mailer} macros. - Milter applications can now request rejected recipients with the SMFIP_RCPT_REJ feature. Rejected recipients are reported with {rcpt_mailer} = "error", {rcpt_host} = enhanced status code, and {rcpt_addr} = descriptive text. This feature requires "milter_protocol = 6" or higher (default as of Postfix 2.6). - Milters can now replace the envelope sender address with the SMFIR_CHGFROM request, and can add recipients with SMFIR_ADDRCPT_PAR. These implementations ignore ESMTP command parameters and log a warning message as follows: warning: 100B22B3293: cleanup_chg_from: ignoring ESMTP arguments "whatever" warning: 100B22B3293: cleanup_add_rcpt: ignoring ESMTP arguments "whatever" [Incompat 20090428] The default milter_protocol setting is increased from 2 to 6; this enables all available features up to and including Sendmail 8.14.0. The new milter_protocol setting may break compatibility with older Milter libraries or applications, and may cause Postfix to log warning messages such as: warning: milter inet:host:port: can't read packet header: Unknown error : 0 warning: milter inet:host:port: can't read packet header: Success warning: milter inet:host:port: can't read SMFIC_DATA reply packet header: No such file or directory To restore compatibility, specify "milter_protocol = 2" in main.cf. Major changes - security ------------------------ [Incompat 20080726] When a mailbox file is not owned by its recipient, the local and virtual delivery agents now log a warning and defer delivery. Specify "strict_mailbox_ownership = no" to ignore such ownership discrepancies. Major changes - smtp server --------------------------- [Feature 20080212] check_reverse_client_hostname_access, to make access decisions based on the unverified client hostname. For safety reasons an OK result is not allowed. [Feature 20090210] With "reject_tempfail_action = defer", the Postfix SMTP server immediately replies with a 4xx status after some temporary error, instead of executing an implicit "defer_if_permit" action. [Feature 20090215] The Postfix SMTP server automatically hangs up after replying with "521". This makes overload handling more effective. See also RFC 1846 for prior art on this topic. [Feature 20090228] The Postfix SMTP server maintains a per-session "improper command pipelining detected" flag. This flag can be tested at any time with reject_unauth_pipelining, and is raised whenever a client command is followed by unexpected commands or message content. The Postfix SMTP server logs the first command pipelining transgression as "improper command pipelining after from []". [Feature 20090212] Stress-dependent behavior is enabled by default. Under conditions of overload, smtpd_timeout is reduced from 300s to 10s, smtpd_hard_error_limit is reduced from 20 to 1, and smtpd_junk_command_limit is reduced from 100 to 1. This will reduce the impact of overload for most legitimate mail. [Feature 20080629] The Postfix SMTP server's SASL authentication was re-structured. With "smtpd_tls_auth_only = yes", SASL support is now activated only after a successful TLS handshake. Earlier Postfix SMTP server versions could complain about unavailable SASL mechanisms during the plaintext phase of the SMTP protocol. [Incompat 20080510] In the policy delegation protocol, certificate common name attributes are now xtext encoded UTF-8. The xtext decoded attributes may contain any UTF-8 value except non-printable ASCII characters. Major changes - performance --------------------------- [Feature 20090215] The Postfix SMTP server automatically hangs up after replying with "521". This makes overload handling more effective. See also RFC 1846 for prior art on this topic. [Feature 20090212] Stress-dependent behavior is enabled by default. Under conditions of overload, smtpd_timeout is reduced from 300s to 10s, smtpd_hard_error_limit is reduced from 20 to 1, and smtpd_junk_command_limit is reduced from 100 to 1. This will reduce the negative impact of server overload for most legitimate mail. [Feature 20090109] Specify "tcp_windowsize = 65535" (or less) to work around routers with broken TCP window scaling implementations. This is perhaps more convenient than collecting tcpdump output and tuning kernel parameters by hand. With Postfix TCP servers (smtpd(8), qmqpd(8)), this feature is implemented by the Postfix master(8) daemon. To change this parameter without stopping Postfix, you need to first terminate all Postfix TCP servers: # postconf -e master_service_disable=inet # postfix reload This immediately terminates all processes that accept network connections. Then you enable Postfix TCP servers with the updated tcp_windowsize setting: # postconf -e tcp_windowsize=65535 master_service_disable= # postfix reload If you skip these steps with a running Postfix system, then the tcp_windowsize change will work only for Postfix TCP clients (smtp(8), lmtp(8)). Of course you can also do "postfix stop" and "postfix start", but that is more disruptive. Major changes - tls ------------------- [Incompat 20090428] The Postfix SMTP client(!) no longer tries to use the obsolete SSLv2 protocol by default, as this may prevent the use of modern SSL features. Lack of SSLv2 support should never be a problem, since SSLv3 was defined in 1996, and TLSv1 in 1999. You can undo the change by specifying empty main.cf values for smtp_tls_protocols and lmtp_tls_protocols. The Postfix SMTP server maintains SSLv2 support for backwards compatibility with ancient clients. [Feature 20081010] Controls for the protocols and ciphers that Postfix will use with opportunistic TLS. The smtp_tls_protocols, smtp_tls_ciphers, and equivalent parameters for lmtp and smtpd provide global settings; the SMTP client TLS policy table provides ciphers and protocols settings for specific peers. Code by Victor Duchovni. Details are given in the TLS_README and postconf(5) documents. [Feature 20081108] Elliptic curve support. This requires OpenSSL version 0.9.9 or later. Major changes - address verification ------------------------------------ [Incompat 20080428] Postfix SMTP server replies for address verification have changed. unverified_recipient_reject_code and unverified_sender_reject_code now handle "5XX" rejects only. The "4XX" rejects are now controlled with unverified_sender_defer_code and unverified_recipient_defer_code. [Feature 20080428] Finer control over the way Postfix reports address verification failures to remote SMTP clients. - unverified_sender/recipient_defer_code: the numerical Postfix SMTP server reply code when address verification failed due to some temporary error. - unverified_sender/recipient_reject_reason: fixed text that Postfix will send to the remote SMTP client, instead of sending actual address verification details. Major changes - dsn ------------------- [Feature 20090307] New "lmtp_assume_final = yes" flag to send correct DSN "success" notifications when LMTP delivery is "final" as opposed to delivery into a content filter. Major changes - file organization --------------------------------- [Incompat 20080207] According to discussions on the mailing list, too many people are breaking newly installed Postfix by overwriting the new /etc/postfix files with versions from an older release, and end up with a broken configuration that cannot repair itself. For this reason, postfix-script, postfix-files and post-install are moved away from /etc/postfix to $daemon_directory. Major changes - header rewriting -------------------------------- [Incompat 20090330] Postfix now adds (Resent-) From:, Date:, Message-ID: or To: headers only when clients match $local_header_rewrite_clients. Specify "always_add_missing_headers = yes" for backwards compatibility. Adding such headers can break DKIM signatures that cover headers that are not present. For compatibility with existing logfile processing software, Postfix will log ``message-id=<>'' for messages without Message-Id header. Major changes - lmtp client --------------------------- [Feature 20090307] New "lmtp_assume_final = yes" flag to send correct DSN "success" notifications when LMTP delivery is "final" as opposed to delivery into a content filter. Major changes - logging ----------------------- [Incompat 20090330] Postfix now adds (Resent-) From:, Date:, Message-ID: or To: headers only when clients match $local_header_rewrite_clients. Specify "always_add_missing_headers = yes" for backwards compatibility. Adding such headers can break DKIM signatures that cover headers that are not present. This changes the appearance of Postfix logging: to preserve compatibility with existing logfile processing software, Postfix will log ``message-id=<>'' for messages without Message-Id header. Major changes - mime -------------------- [Feature 20080324] When the "postmap -q -" command reads lookup keys from standard input, it now understands RFC822 and MIME message format. Specify -h or -b to use headers or body lines as lookup keys, and specify -hm or -bm to simulate header_checks or body_checks. Major changes - miscellaneous ----------------------------- [Feature 20090109] Support to selectively disable master(8) listener ports by service type or by service name + type. Specify a list of service types ("inet", "unix", "fifo", or "pass") or "name.type" tuples, where "name" is the first field of a master.cf entry and "type" is a service type. Examples: to turn off the main SMTP listener port, use "master_service_disable = smtp.inet"; to turn off all TCP/IP listeners, use "master_service_disable = inet". Changing this parameter requires "postfix reload". Major changes - sasl -------------------- [Feature 20090418] The Postfix SMTP server passes more information to the Dovecot authentication server: the "TLS is active" flag, the server IP address, and the client IP address. [Feature 20080629] The Postfix SMTP server's SASL authentication was re-structured. With "smtpd_tls_auth_only = yes", SASL support is now activated only after a successful TLS handshake. Earlier Postfix SMTP server versions could complain about unavailable SASL mechanisms during the plaintext phase of the SMTP protocol.