Mail is flowing again as of about 20 minutes ago. We ran into issues with the way Windows Server 2012 handles short-file-name paths. You should now be able to send/receive email on your computer, phone, or tablet. If by chance you had Outlook open while the mail services were down, you may have to close Outlook and re-open and/or reboot the computer.
Web Mail will remain unavailable for a while longer. We will post again when it is available.