Aaron Cake wrote:
This definitely is a problem, but not just like you describe. Spammers themselves do the same thing based simply on the way SMTP works. At the ISP I work for we've had tons of problems with a spammer (or multiple spammers) using an address from one of our domains as the sender and then a bad recipient address and sending thousands of messages. The recipient server bounces messages back to the apparent sender, effectively mail-bombing them like you describe. Its even worse when the victim address doesn't actually exist because then the postmaster address at both ends gets all kinds of warnings as well.Imagine if I decided to use a spam fitler against someone else...I make an email that contains known rejected words. I send that email, setting the "FROM" address and header to be that of my victim. If I send out hundreds of these messages, I can use someone else's spam filter to mail-bomb my victim with "rejected" messages.
I've seen some ISPs have started to block mail sent by <> to put an end to this sort of thing, but that doesn't seem like a very good solution as it probably blocks legitimate bounce messages.
Chris