Outlook Email was not accessible for some users
4/21/2020, 7:45 AM: Microsoft resolved this issue last night, and all mailboxes should now be accessible. If you continue to experience issues, please contact the ATUS Help Desk.
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4/20/2020, 6:30 PM: Microsoft is investigating an issue that is causing some users to experience "error 500" when accessing their mailbox from any protocol (Outlook desktop app, mobile app, Web app, IMAP). There is no workaround at this time.