How I fight spam
Sic the mutt on it
When SpamAsssassin doesn't find spam, I teach it: ESC+S (ESC + Capital S)

From my ~/.muttrc:
macro index \eS "<pipe-message>/home/mike/bin/spam-blist\n<save-message>=Spam-Uncaught\n"

The contents of spam-blist:
cat - | /usr/local/bin/spamassassin -d |
/usr/local/bin/spamassassin -r