Amavis - MySQL server has gone away
I found this error cluttering my system logs:
May 26 06:39:16 zeus amavis[10981]: (10981-04) NOTICE: reconnecting in response to: err=2006, HY000, DBD::mysql::st execute failed: MySQL server has gone away at (eval 86) line 166, GEN54 line 5.
After a bit of debugging it turns out amavis keeps an open connection to mysql and depending on your wait_timeout setting it might lose the connection and need to reconnect.
In order to fix this you just need to increase your wait_timeout to a comfortable value.
mysql set global wait_timeout=28800;
Query OK, 0 rows affected (0.00 sec)
You also need to edit your my.cnf file to make sure the change is persistent across mysql restarts.