Can you be more specific than "not working"?
What domain is this, what's the ticket # from your support inquiry about this, are you having problems retrieving mail, sending mail, receiving mail (and if so, trouble receiving mail from yourself, external accounts, or both).
While it's odd that so many people seem to be having problems at the same time, so far I haven't seen evidence of any big system-wide problem that began today. If you're going to post here about a mail problem, please also submit a support request if you haven't already, and please make sure to include some information about the nature of your problem.
Much as I'd like to fix everyone's individual problems, I'm mostly interested in making sure there isn't a more general problem here.