First I would recomment you upgrade to Spam Assassin 3.x - It's much better.
Good point Marc, that's a better solution in general. I do recommend that over my previous advice of just adding antidrug.cf.
However, if they are stuck on 2.64 due to perl versions or some such thing, adding antidrug.cf and Mail::SpamCopURI covers a lot of the problem cases for 2.64.
Disclaimer: I'm the author of antidrug.cf, bias for the tools I made is obvious (I forgot to add that to my first message)
