I can't believe my spam-attack today

[mstudio]

Since midnight, I have been receiving a "Mail Delivery System"-type email at the rate of 1 to 3 a minute. That's well over 1800 so far today. I can't keep up trying to delete them from my server. It's an email address I haven't used in awhile, but it's linked to one of my domains, so I can't just close it.

Someone or something obviously got the address and has been bombarding hyperspace. I don't understand to what end, however.

I don't know if I can stop it or not.

Any ideas?