The entire University of Miami domain seems to be having holiday troubles, and it's taken my regular mail server down with it. UM is officially closed for the holidays at present, so I don't know how fast the repairs will be.
If you need to reach me urgently…use the phone.
Or, there's always my backup email address of email@example.com, but I don't check that as obsessively as I do the usual account.
Update (12/21): It's working now.