I think I have figured something out about spammers. If you setup a catchall rule in the virtual map table for a domain such that *@mydomain.com will always get delivered to someone, then the spammers will figure it out. And when they do they will send a ton of spam spoofed to be from various usernames at your domain.

This has three major problems:

  • You get emails from idiots that do not read mail headers telling you not to spam them anymore.
  • You get email from auto-spam rejection bots (that IMHO add to the spam)
  • You get a ton of postmasters sending failure to deliver errors.

All three of these added up was equal to about 2500 spam/spam-bounce/postmaster-return emails per day for one of my domains. Today I killed the *@domain mapping and I had one email make it through my normal spam filter. And the total email sent to me dropped several orders.

So the lesson to learn here: Do not use *@domain maps.