SpamBox incorrectly marks messages as spam

Symptoms

You notice that SpamBox is marking messages as spam that should not be considered spam.

Cause 

This can occur if there is corruption in the SpamAssassin Bayesian database.

Resolution

Move aside the bayes_ files from the /home/$user/.spamassassin directory. SpamAssassin will automatically re-create these files and will start using the Bayes database in scoring again once the number of emails in the database has reached 200.

The following article has more details on how to teach SpamAssassin to better identify spam:

How to teach Spam Assassin to identify more SPAM