I'm having the same problem.... since yesterday evening. I've lost quite a bit of important email already, since by chance I had sent out a lot yesterday that would get replied.
A DH support fellow characterized it a small, temporary problem that would not cause any permanent harm. I found this almost as frustrating as the email problem.
I'm in need of a hosting service, that understands the high importance of working email in a business setting. DH used to be much more expensive, but used to be that way. Now I can get a zillion domains for a dollar, but... I'd rather pay several times as much, and have my email work.
I sent another support request this morning, and have had no indication that DH is aware of this problem or is working on it. No announcements, no emerg status page, etc.