[An on-line version of this announcement will be available at https://www.postfix.org/announcements/postfix-3.9.1.html]
Fixed with Postfix 3.9.1:
The mail_version configuration parameter did not have a three-number value (3.9 instead of 3.9.0; it still had the two-number version from the development releases postfix-3.9-yyyymmdd). This broke pathnames derived from the mail_version value, such as shlib_directory. Problem reported by Michael Orlitzky.
Fixed with Postfix 3.9.1, 3.8.7, 3.7.12, 3.6.16:
Bugfix (defect introduced: Postfix 2.9, date 20111218): with "smtpd_sasl_auth_enable = no", the permit_sasl_authenticated feature ignored information that was received with the XCLIENT LOGIN command, so that the client was treated as unauthenticated. This was fixed by removing an unnecessary test. Problem reported by Antonin Verrier.
Bugfix (defect introduced: postfix 3.0): the default master.cf syslog_name setting for the relay service did not preserve multi-instance information, which complicated logfile analysis. Found during a support discussion.
Bugfix (defect introduced: Postfix 2.3, date 20051222): file descriptor leak after failure to connect to a Dovecot auth server. The impact is limited because Dovecot auth failures are rare, there are limits on the number of retries (one), on the number of errors per SMTP session (smtpd_hard_error_limit), on the number of sessions per SMTP server process (max_use), and on the number of file handles per process (managed with sysctl). Found during code maintenance.
Bugfix (defect introduced: Postfix 3.4, date 20190121): the postsuper command failed with "open logfile '/path/to/file': Permission denied" when the maillog_file parameter specified a filename and Postfix was not running. This was fixed by opening the maillog_file before dropping root privileges. Found during code maintenance.
Bugfix (defect introduced Postfix 3.0). No autodetection of UTF8 text when missing message headers were automatically added by Postfix (for example, a From: header with UTF8 full name information from the password file). This caused Postfix to send UTF8 in message headers without using the SMTPUTF8 protocol. Problem reported by Michael Tokarev.
You can find the updated Postfix source code at the mirrors listed at https://www.postfix.org/.