Spamassassin has caught 15,000 spam emails in the past 6 months. Great program!
The best feature? You can tweak it as needed.
I have installed Spamassassin under Debian Linux.
If I regularly get spam of a certain kind, I write my own regular expression rule for it and eliminate it.
Spamassassin is wonderful for reducing fear. I no longer fear spam because I know I can eliminate it if it gets overwhelming.