I have a client that is getting heavily spammed.. it's the 15th of the month and POP3 bandwidth is almost 100 GB (yes GB..lol!) there are only 7 e-mail account on this domain. I installed SpamAssassin set it to 5 and setup 10-20 filters reject most of the junk. I don't see much of a change in POP3 bandwidth. Correct me if I'm wrong, the server still receives the message using up bandwidth in order to analyze determine a spam score.
I stumbled across faking MX records, for thoes unaware--basically you set a bogus server as the lowest and highest MX records with the working server's MX record in the middle.
fake.mydomain.com 1 realmx.mydomain.com 2 fake2.mydomain.com 3
The theory is, since majority of the spam is generated from Windows-based zombies and quite a few will query for the the highest MX record to spam since usually they're usually backup servers that don't filter spam. The lowest fake MX-record is for the rest of the spammers.. and generally spammers don't retry after failures.
Has anyone tried this? Does it help? Does it delay or cause issues with mail delivery? Does anyone else have a better solution?