How do I tell if somebody is relaying on my server?

[MrSpeed]

I have a virtual server reseller account.
Once a month somebody sends out a newsletter which floods my default mail drop because there are bad email addresses in the mailing list. The domain that sends the newsletter has not been on my server for almost a year.
I exceed my disk storage quota when this happens.

I can not figure out why the bad email are getting bounced back to me. Is there a way to set up a filter to block the bounced mails?

The person is using his laptop and some application to send the emails. Doesn't that still require a smpt server?

Is it possible to post the mail header here so someone can help me figure it out?

[dmorison]

I can not figure out why the bad email are getting bounced back to me. Is there a way to set up a filter to block the bounced mails?

You say that the domain hasn't been on your server for a year; but it sounds like you are still listed as the MX (mail exchanger) for that domain.

You need to get hold of whoever is responsible for the DNS records of that domain (use whois) and have them change or delete the MX records so that they no longer point to your server.

What really doesn't make sense is not why you are getting the bounces; but why the sender doesn't want to receive legitimate replies to thier mailing - because if you are receiving the bounces then you would also receive any legitimate reply from a real recipient.

[MrSpeed]

The truth has come out.
I never removed the directory for the domain. He is using the mirror domain still on my server to manage the mailing list.