Since 12:42 PM EST today, FogBugz On Demand accounts have not been processing incoming email messages directed to cases@{your FogBugz site}.fogbugz.com. All incoming mail is still present, but has not yet been processed by FogBugz. We are actively working on a solution to this problem and will post to status.fogcreek.com when it is resolved.
Outgoing mail and additional custom mailboxes, e.g. bugs@example.com, are not affected by this issue.