An on-line version of this announcement is available at http://www.postfix.org/announcements/postfix-2.5.9.html
The legacy releases Postfix 2.5.9, 2.4.13 and 2.3.19 addresses the defects described below.
Do not use Postfix releases 2.5.8, 2.4.12, or 2.3.18. These contain a DNS workaround that causes more trouble than it prevents. It is removed until further notice.
Defects fixed with Postfix 2.5.9, 2.4.13 and 2.3.19:
The Postfix Milter client got out of step with a Milter application after the application sent a "quarantine" request at end-of-message time. The Milter application would still be in the end-of-message state, while Postfix would already be working on the next SMTP event, typically, QUIT or MAIL FROM. In the latter case, Milter responses for the previously-received email message would be applied towards the next MAIL FROM transaction. This problem was diagnosed with help from Alban Deniz.
The Postfix SMTP server would abort with an "unexpected lookup table" error when an SMTPD policy server was mis-configured in a particular way.
The source code is available from ftp://ftp.porcupine.org/mirrors/postfix-release/index.html and from the mirrors listed at http://www.postfix.org/download.html.