[GTALUG] Fwd: Cogeco E-Mail not bouncing unknown mailboxes?

Hi All, A friend is having issues changing his contact info on a domain. The Admin contact E-Mail address points to a Cogeco mailbox that was attached to an account that was closed years ago. However, it seems Cogeco doesn't bounce messages to non-existent mailboxes. So he's stuck. And his domain is give from the DNS servers, which is a drag. Thoughts?