Dumb question SPAM or UBE

[shane mullins]

We have been running Spamassassin for several years now.  It has done a super job for our school system.  Spamassassin has opened many doors for OpenSource software in our division.  I just have one dumb question that I have not been able to answer.  Why is some email flagged as SPAM and some as UBE?    Thanks Shane