I would try spamassassin :

http://spamassassin.rediris.es/index.html

t will allow you to rate spam and based on the 'score' either delete mails, add headers, change the subject etc.

You will probably need to set up a *nix box to do the checking, but it should be fairly simple & best of all it's open source.

If you want to offer your users a good service you could set them up with disposable addresses, see this tutorial:

http://www.antionline.com/showthread...hreadid=247544

Yougenerate a 'random' email address that will forward to their account for a preiod of time (days/weeks etc) that they select and after that time mail bounces. They then can use this address for using on sites where they can't be certain that the site id okay.


Steve