assp is good, but ...

I use the Anti Spam SMTP Proxy: http://assp.sourceforge.net/
and I was encountering spam coming in that mailed to postmaster and whomever else was also in "To:".

It turned out that in "Recipients", I had Skip Spam Checks for Postmaster Catchall (sendAllPostmasterNP) -- and abuse checked, which basically precluded the check for "but not if other people are also in 'To:'".

After unchecking this, (and sendAllAbuseNP), the spam dropped.