This is the Postfix 3.11 stable release. The stable Postfix release is called postfix-3.11.x where 3=major release number, 11=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-3.12-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 3.9 or earlier, please read RELEASE_NOTES-3.10 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 - database ------------------------ [Feature 20250321] Safety: the SQLite client now logs a warning when a query uses double quotes instead of the Postfix-recommended single quotes. Only the recommended form is protected against SQL injection. [Feature 20250509] Support to run all memcache lookup keys through an OpenSSL digest function. This prevents a database access error when lookup keys may exceed the memcache server's key length limit (usually, 250 bytes). [Feature 20250624] Support for a new "debug:" pseudo lookup table. Specify debug:maptype:mapname to encapsulate a maptype:mapname lookup table and log all access. This builds on existing but unused code to log table access. Contributed by Richard Hansen. [Infrastructure 20250626] Overhauled in-memory lookup table life-cycle management; overhauled sharing/isolation for proxied lookup tables. Major changes - deprecation --------------------------- [Feature 20250609] smtp_tls_enforce_peername and lmtp_tls_enforce_peername are now officially deprecated. Postfix will log a warning until the features are deleted. See DEPRECATION_README for a summary of deprecated and deleted features. [Feature 20251027] This adds 12 more deprecation warnings for parameters that have been renamed in the past, and that still provide a backwards-compatible default value for their replacement. The parameters deprecated by this change are: authorized_verp_clients, fallback_relay, lmtp_per_record_deadline, postscreen_blacklist_action, postscreen_dnsbl_ttl, postscreen_dnsbl_whitelist_threshold, postscreen_whitelist_interfaces, smtpd_client_connection_limit_exceptions, smtp_per_record_deadline, tlsproxy_client_level, tlsproxy_client_policy, virtual_maps. [Feature 20251028] Deprecate the smtp_cname_overrides_servername and lmtp_cname_overrides_servername parameters, and delete documentation that has been obsolete since Postfix 2.11. Major changes - logging ----------------------- [Feature 20250910] TLS feature policy status summary in delivery status logging. This shows the desired and actual TLS security level enforcement status and, if a message requests REQUIRETLS, the REQUIRETLS policy enforcement status. For a list of examples see https://www.postfix.org/postconf.5.html#smtp_log_tls_feature_status [Feature 20251216] After a delivery failure, the bounce daemon logged ": sender non-delivery notification: " only if the notification was queued successfully. The bounce daemon now always logs this, making Postfix behavior easier to understand. Visible changes for logfile analyzers: - The bounce daemon now logs ": sender non-delivery notification: " BEFORE the cleanup daemon logs activity with "". Previously, the bounce daemon logged the old<=>new queue ID connection later, which made logfile analysis more difficult. - The bounce daemon now logs a logfile record ": sender notification failed to
: " when the notification was not queued. In some cases it will log ": sender notification failed to
" (without the reason). In those cases the failure reason was already logged by lower-level code, but without the queue ID. Major changes - management tool integration ------------------------------------------- [Feature 20251124] Basic JSON output support with "postconf -j|-jM|-jF|-jP", "postalias -jq|-js", "postmap -jq|-js", and "postmulti -jl". No support is planned for JSON input support. Major changes - milter support ------------------------------ [Feature 20251208] Improved Milter error handling for messages that arrive over a long-lived SMTP connection, by changing the default milter_default_action from "tempfail" to the new "shutdown" action (i.e. disconnect the remote SMTP client). This avoids a worst-case scenario where after a single Milter error, Postfix would tempfail all messages that the client sends over a long-lived connection, even if the Milter error was only temporary. Major changes - mime support ---------------------------- [Feature 20251104] New non_empty_end_of_header_action parameter with the cleanup(8) server action when a primary message header is terminated with a non-empty line: 1) fix_quietly: Insert an empty line before the offending text (the backwards-compatible default), 2) add_header: Insert a MIME-Error: header before inserting an empty line, or 3) reject: Log a "mime-error" and reject the message. Note that the 'empty line' separator is not used for DKIM signature checks. Therefore, adding a missing separator does not break DKIM. Major changes - mta-sts ----------------------- [Feature 20250906] Workaround for an interface mis-match between the Postfix SMTP client and MTA-STS policy plugins. This introduces a new parameter "smtp_tls_enforce_sts_mx_patterns" (default: "yes"). The MTA-STS plugin configuration needs to enable TLSRPT support, so that it forwards STS policy attributes to Postfix. This works even if Postfix TLSRPT support is disabled at build time or at runtime. With the above two configurations, the Postfix SMTP client will connect to an MX host only if its name matches any STS policy MX host pattern, and will match a server certificate against the MX hostname. Otherwise, the old behavior stays in effect: connect to any MX host listed in DNS, and match a server certificate against any STS policy MX host pattern. This code was published first in Postfix 3.11, and later back-ported to Postfix 3.10.5. Major changes - portability --------------------------- [Feature 20241201] Support for the C23 built-in bool type. Older Postfix releases have been updated with a makedefs script that disables C23 built-in bool support. Major changes - postqueue ------------------------- [Feature 20251218] the postqueue (and mailq) command now also lists recipients in bounce logfiles (in JSON output, this uses a new object member 'bounce_reason' instead of the existing 'delay_reason'). Such recipients have already been deleted from the message queue file, but they are still pending the creation of a non-delivery status notification message that will be returned to the sender. Major changes - relocated_maps ------------------------------ [Feature 20250608] Specify "relocated_prefix_enable = no" to disable the hard-coded prefix "5.1.6 User has moved to " that is by default prepended to all relocated_maps lookup results. This setting requires that the table contains responses with both custom enhanced status code (X.Y.Z) and text. For details, see "man 5 relocated" or https://www.postfix.org/relocated.5.html . Major changes - requiretls -------------------------- [Feature 20241111] Support for the REQUIRETLS verb in SMTP. This, and everything that was added later through 2025, is described in REQUIRETLS_README. [Feature 20250120] After a certificate check fails, or a remote SMTP server does not announce REQUIRETLS support, the Postfix SMTP client will override the RFC 8689 5.x.x. status and treat it as a soft error, until there are no more alternate MX servers to try. [Feature 20250827] New parameter requiretls_redact_dsn (default: yes) to redact bounce messages as described in RFC 8689 section 5, so that they don't need REQUIRETLS support on every hop in the return path. [Feature 20250827] smtp_requiretls_policy and lmtp_requiretls_policy for responsible REQUIRETLS policy enforcement. REQUIRETLS must be enforced with care, because at this time most domains do not publish DANE or MTA-STS policies, and most MTAs and content filters do not support REQUIRETLS. [Feature 20250916] support for a "Require-TLS-ESMTP: yes" header to propagate an ESMTP REQUIRETLS request through a FILTER_README or SMTPD_PROXY_README style content filter. This header is detected or added by the cleanup daemon and by the before-proxy-filter Postfix SMTP server. This feature is enabled by default with "requiretls_esmtp_header = yes". The Require-TLS-ESMTP header will be visible to local and remote recipients. This feature can safely be disabled when a configuration does not use REQUIRETLS, or does not use FILTER_README or SMTPD_PROXY_README style content filters. Major changes - smtp server --------------------------- [Feature 20250801] smtpd_reject_filter_maps support to selectively replace a reject response from the Postfix SMTP server, or from a program that replies through the Postfix SMTP server. Major changes - smtputf8 ------------------------ [Feature 20250122] New Postfix sendmail command option "-O smtputf8" to request that deliveries over SMTP use the SMTPUTF8 extension. This reuses logic that was introduced for REQUIRETLS. [Feature 20250824] When a message needs to be delivered with SMTPUTF8, but a remote server does not support it, the Postfix SMTP client may now try alternate servers instead of returning the message immediately. This reuses code that was implemented for REQUIRETLS. Major changes - tls support --------------------------- [Feature 20250623] This changes the Postfix SMTP client smtp_tls_security_level default value to "may" if Postfix was built with TLS support, and the compatibility_level is 3.11 or higher. There is no change to the default lmtp_tls_security_level value. It remains empty, because there is no default TLS security level that makes sense for connections over UNIX-domain and loopback TCP and non-loopback TCP sockets. There also is no equivalent change for Postfix SMTP server TLS security levels, because changing smtpd_tls_security_level is not sufficient. Server-side TLS requires that at least one private key and corresponding public-key certificate chain are configured. [Feature 20251029] Debugging: depending on OpenSSL build options, "posttls-finger -L ssl-debug" will decode TLS handshake messages. [Feature 20251102] Post-quantum cryptography support: with OpenSSL 3.5 and later, change the tls_eecdh_auto_curves default value to avoid problems with network infrastructure that mis-handles TLS hello messages larger than one (Ethernet) TCP segment. This problem is more generally known as "protocol ossification". Major changes - tlsrpt ---------------------- [Incompat 20250601] the default smtp_tlsrpt_skip_reused_handshakes setting was changed from "yes" to "no". The new default is enabled with compatibility level >= 3.11.