Other Trick For Blocking Spam

This section is for other tricks to block spam that may or may not directly relate to SpamAssassin.

Fake MX Records

Email is supposed to be sent to the lowest numbered MX record first with the higher MX records being backup servers. Spammers often with try the highest MX record first thinking that the backup servers have less spam filtering than the main email server. They try the highest MX record and then never come back. So I set my highest MX record to point to an IP address that always returns a temporary "Come Back Later" error.

A real email will retry and get through. But the spammer will just go away. This trick saves having to process about 25,000 messages a day on my server.