Same experience here running a client's email server (Postfix, Dovecot, SpamAssassin, ClamAV) for 2 years. Spam filtering techniques (and subsequent techniques

Same experience here running a client's email server (Postfix, Dovecot, SpamAssassin, ClamAV) for 2 years. Spam filtering techniques (and subsequent techniques for circumventing them) are constantly changing.