Honestly, it may seem a bit presumptuous, but most of us are probably on
unix mail servers.  It also seems obvious that most of us probably use
procmail.

That being the case, might I suggest using Spambouncer?
http://www.spambouncer.org.  Just add  /path/to/spambouncer/folder/sb.rc to
your list of recipes, and turn on the switches you want and you're set.  I
don't get spam.  Period.

Just a thought anyway. :)