I'm running qmail-1.03.
A spammer cleverly sends mail to:
non-existent-user@mail.myserver.com
My server turns around and tries to bounce the message (or at least that is what I think is happening), and somehow ends up sending the same spam message to hundreds of email addresses set by the spammer.
I've been trying to track down the weakness in my server that allows this kind of abuse, but so far I've not been successful.
I have set Catchall to "Deleted" for myserver.com.
I've also aliased "mail.myserver.com" to "myserver.com".
I've checked my server to see if it's an open relay, but it's not.
Finally, when I sent a message to:
non-existent-user@mail.myserver.com
I don't get a bounce back.
What else should look at to solve this problem?
Thx.