We are running a multi-server zimbra OSS 5.0.16. Yesterday, zimbra became unresponsive. Having a look on the server that stores e-mail, zmcontrol status was showing mysql.server not running.

Looking at /opt/zimbra/log/mysql_error.log, we have:
090916 4:03:59 InnoDB: Started; log sequence number 0 1908187150
090916 4:03:59 [Note] /opt/zimbra/mysql/libexec/mysqld: ready for connections.
Version: '5.0.67-log' socket: '/opt/zimbra/db/mysql.sock' port: 7306 Source distribution
090916 17:10:49 [Note] /opt/zimbra/mysql/libexec/mysqld: Normal shutdown

At 04:00, we backup the server, so services are stopped and restarted after backup. At 17:10:49, mysql was normally stopped, for an unknown reason.

Any help appreciated to understand what happened.
-- Laurent.