Why did MDaemon just restart?

For those wondering why MDaemon unexpectedly restarted, it’s due to a SecurityPlus update.  Alt-N has a knowledgebase article discussing this behaviour.

If you prefer to avoid this situation in the future, there is an option available (also described in the KB article) to avoid automatic updates, however, be certain to monitor for updates manually as several times in the past SecurityPlus was updated due to changes in the definitions update process.