Answer: This is not an unusual situation at all. It happens to all of us at one time or another. We call it 'backscatter'. Fortunately the event seems to be short-lived and the lasting effects are nil.

What happens is that a spammer has chosen your email address at random as the 'From' address of a batch of their spam emails. They are sent from whatever machines on the internet they have control of, and they make sure to cover their tracks so that no-one can say who sent them.

As is typical, a proportion of the emails they send will be undeliverable, and the receiving mail servers respond by dutifully sending 'Delivery Status Notification' messages back to the 'From' address specified in the headers of the email. That means you.

You'd think that email would be a bit more secure, but it was devised in happier times when the concept of spam hadn't even been considered.

Rest assured that our mail servers have not been compromised, and the emails did not come from us. However, as valid DSN messages, we cannot block them out either, since the DSN messages come from reliable sources and are not considered spam.

Fortunately no spammer can afford to over-use the same From address, so they quickly move on.