An on-line version of this announcement is available at http://www.postfix.org/announcements/postfix-2.5.7.html
Postfix legacy releases 2.5.7, 2.4.11 and 2.3.17 contain fixes that were already included with Postfix versions 2.6 and 2.7.
(low) The installation/upgrade procedure did not automatically create the data_directory.
(medium) In the "new queue manager", the _destination_rate_delay code needed to postpone the job scheduler updates after delivery completion, otherwise the scheduler could loop on blocked jobs.
(low) The queue manager used transport_concurrency_failed_cohort_limit instead of transport_destination_concurrency_failed_cohort_limit as documented.
(medium) The postsuper command re-enabled the SIGHUP signal when it was set to "ignore". This could result in random "Postfix integrity check failed" errors at boot time (POSIX SIGHUP death), causing Postfix not to start automatically.
You can find the source code and patches at the mirrors listed at