Wow. What a tough problem. It's also one that I'll have to try to deal with in a few years so I especially appreciate you paving the way. ;-)

I think the use of SpamAssassin and Mozilla is a good starting point.

I have the same reservations about automated replies that BrowserUk voiced. But if you do go that route, FIGlet might not be the best choice. A figlet "encoded" string might be almost decipherable to someone who views it in something other than a fixed width font.

-sauoq
"My two cents aren't worth a dime.";