[Mailman-Users] Regular expression for Spam Filter wanted

Hello all, I am running mailman on Debian/Plesk with a Spam-Filter which prefixes headers of spam mails with "***SPAM***". I tried to filter these mails in mailman using spam filter rule "^Subject:\*\*\*SPAM\*\*\*", but that doesn't work. Could you please help me? Thanks, Sascha.