...well, nuts to me.

I take back everything bad I said or hinted at in the previous post.

Seems that when your $ORIGIN is .com, and your MX record is

MX 10 mail.xdroop.com

...the internet obediently tries to send mail to mail.xdroop.com.com, even though it doesn't exist.

I can't believe I missed that.

Literally fifteen seconds after fixing that and pushing it, the spam is flowing again.

So that means everything bad that's happened during my stay with Tera-Byte has been my fault. They have been a perfect host during my stay -- I never had to think about them or worry about them. And I think I got good value during my stay too.