The stable Postfix release is called postfix-2.7.x where 2=major release number, 7=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-2.8-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 2.6 or earlier, read RELEASE_NOTES-2.7 before proceeding. Incompatibility with snapshot 20100728 ====================================== The format of the "postfix/smtpd[pid]: queueid: client=host[addr]" logfile record has changed. When available, the before-filter client information and the before-filter queue ID are now appended to the end of the record. Major changes with snapshot 20100728 ==================================== Improved message tracking across SMTP-based content filters. The logging example below is from an after-filter SMTP server. Here, 951F692462F is a before-filter queue ID, hades.porcupine.org is a before-filter SMTP client, while 6B4A9924782 is the after-filter queue ID, and localhost[127.0.0.1] is the SMTP-based content filter that sends mail into the after-filter SMTP server. postfix/smtpd[4074]: 6B4A9924782: client=localhost[127.0.0.1], orig_queue_id=951F692462F orig_client=hades.porcupine.org[168.100.189.10] Incompatibility with snapshot 20100610 ====================================== Postfix no longer appends the system-supplied default CA certificates to the lists specified with *_tls_CAfile or with *_tls_CApath. This prevents third-party certificates from being trusted and given mail relay permission with permit_tls_all_clientcerts. Unfortunately this change may break certificate verification on sites that don't use permit_tls_all_clientcerts. Specify "tls_append_default_CA = yes" for backwards compatibility. Incompatibility with snapshot 20100101 ====================================== When periodic cache cleanup is enabled (the default), the postscreen(8) server now requires that the cache database supports the "delete" and "sequence" operations. To disable periodic cache cleanup specify a zero postscreen_cache_cleanup_interval value. Major changes with snapshot 20100101 ==================================== Periodic cache cleanup for the postscreen(8) cache database. The time between cache cleanup runs is controlled with the postscreen_cache_cleanup_interval (default: 12h) parameter. Cache cleanup increases the database access latency, so this should not be run more often than necessary. In addition, the postscreen_cache_retention_time (default: 1d) parameter specifies how long to keep an expired entry in the cache. This prevents a client from being logged as "NEW" after its record expired only a little while ago. Incompatibility with snapshot 20091209 ====================================== The postscreen daemon now checks the permanent whitelist before the permanent blacklist. This makes the whitelist easier to use for its intended purpose, which is to receive mail. Incompatibility with snapshot 20091008 ====================================== NOTE: You must stop and start the Postfix master daemon before you can use the postscreen(8) daemon. This is needed because the Postfix "pass" master service type did not work reliably on some systems. Major changes with snapshot 20091008 ==================================== Prototype postscreen(8) server that runs a number of time-consuming checks in parallel for all incoming SMTP connections, before clients are allowed to talk to a real Postfix SMTP server. It detects clients that start talking too soon, or clients that appear on DNS blocklists, or clients that hang up without sending any command. By doing these checks in a single postscreen(8) process, Postfix can avoid wasting one SMTP server process per connection. A side benefit of postscreen(8)'s DNSBL lookups is that DNS records are already cached before the Postfix SMTP server looks them up later. postscreen(8) maintains a temporary whitelist of positive decisions. Once an SMTP client is whitelisted, it is immediately forwarded to a real Postfix SMTP server process without further checking. By default, the program logs only statistics, and it does not run any checks on clients in mynetworks (primarily, to avoid problems with buggy SMTP implementations in network appliances). The logging function alone is already useful for research. postscreen(8) can be configured to drop clients that start talking too soon, or clients that appear on DNS blocklists. For details, see below. postscreen(8) has been tested on FreeBSD and Linux systems. It probably needs additional work before it can be used on Solaris. This snapshot adds three new entries to the master.cf file. To enable the postscreen(8) service and log client information without blocking mail: 1 - Comment out the "smtp inet ... smtpd" service in master.cf, including any "-o parameter=value" entries that follow. 2 - Uncomment the new "smtpd pass ... smtpd" service in master.cf, and duplicate any "-o parameter=value" entries from the smtpd service that was commented out in step 1. 3 - Uncomment the the new "smtp inet ... postscreen" service in master.cf. 4 - Uncomment the new "dnsblog unix ... dnsblog" service in master.cf. This service does DNSBL lookups for postscreen(8) and logs results. 5 - To enable DNSBL lookups, list some DNS blocklist sites in main.cf, e.g., "postscreen_dnsbl_sites = zen.spamhaus.org". Separate domain names with comma or whitespace. Note: you must stop and start the master daemon. This is needed because the Postfix "pass" master service type did not work reliably on all systems. To use the postscreen(8) service to block mail, edit main.cf and specify one or more of: - "postscreen_greet_action = drop", to drop clients that talk before their turn. This alone stops about one third of all known-to-be illegitimate connections to Wietse's mail server. - "postscreen_hangup_action = drop", to waste no time on clients that hang up without sending a command. On Wietse's server, only one percent of illegitimate connections behaves like this. - "postscreen_dnsbl_action = drop", to drop clients that are on DNS blocklists. Different blocklists cover different client categories. There is also support for permanent blacklists and whitelists; see the postscreen(8) manual page for details. Note: right now, postscreen(8) "drop" actions disconnect the client without reporting sender and recipient information. In a future implementation, the connection may instead be passed to a dummy SMTP protocol engine that logs sender and recipient information before dropping the connection.