ASSP is an SMTP proxy server so it can always let the other side know a message has been rejected. All the bounce/double-bounce stuff is eliminated.

Very easy to get going and very effective here* at work. It isn't rules based, so it's light on resources (SpamAssassin brings the same server to its knees easily). The only resource hog is the nightly rebuild of the databases.


* Possible bias: since 99% of spam is some mutation of English, ASSP may be very effective at separating English from Dutch...