An on-line version of this announcement is available at http://www.postfix.org/announcements/postfix-2.6.0.html
Postfix stable release 2.6.0 is available. After Postfix was declared "complete" with version 2.3, the focus has moved towards improving the code/documentation, and updating it for changing environments.
Multi-instance support introduces a new postmulti(1) command to create/add/remove/etc. additional Postfix instances. The familiar "postfix start" etc. commands now automatically start multiple Postfix instances. The good news: nothing changes when you use only one Postfix instance. See MULTI_INSTANCE_README for details.
TLS (SSL) support was updated for elliptic curve encryption. This requires OpenSSL version 0.9.9 or later. The SMTP client no longer uses the SSLv2 protocol by default. See TLS_README for details.
The Milter client now supports all Sendmail 8.14 Milter requests, including requests for rejected recipient addresses, and requests to replace the envelope sender address. See MILTER_README for details.
Postfix no longer adds (Resent-) From:, Date:, Message-ID: or To: headers to email messages with "remote" origins (these are origins that don't match $local_header_rewrite_clients). Adding such headers breaks DKIM signatures that explicitly cover non-present headers. For compatibility with existing logfile processing software, Postfix will log ``message-id=<>'' for email messages that have no Message-Id header.
Stress-adaptive behavior is now enabled by default. This allows the Postfix SMTP server to temporarily reduce time limits and error-count limits under conditions of overload, such as a malware attack or backscatter flood. See STRESS_README for details.
No functionality has been removed, but it is a good idea to review the RELEASE_NOTES file for the usual minor incompatibilities or limitations.
You can find Postfix version 2.6.0 at the mirrors listed at http://www.postfix.org/
The same code is also available as Postfix snapshot 2.7-20090511. Updated versions of Postfix version 2.5, 2.4 and perhaps 2.3 will be released with the same fixes that were already included with Postfix versions 2.6 and 2.7.