Is there any way to determine why a particular message that Zone Alarm Anti-Spam moved to junk mail was treated that way?

I manage the web site for one client whose messages to me are occasionally (but not always) classified as junk. I would like to be able to figure out what the cause of the problem is so that I can fix it once and for all. Can I get Zone Alarm Anti-Spam to report or log the basis for its classification decisions?