Bugfix (introduced: Postfix 3.0): the SMTP daemon did not
reset a previous session's command counts before rejecting
a client that exceeds request or concurrency rates. File:
smtpd/smtpd.c.

Bugfix (introduced: Postfix 3.0): the unionmap did not
propagate table lookup errors.  Based on patch by Roel van
Meer.  Files: util/dict_union.c, util/dict_union_test.*.

Workaround (problem introduced: Postfix 2.11): to avoid
false "not found" errors with MySQL map queries that contain
UTF8-encoded text, specify "option_group = client" in Postfix
MySQL configuration files.  This will be the default setting
with Postfix 3.2 and later.