You can't access a mailbox by using EWS in Office 365 Dedicated/ITAR (vNext)

Symptoms

You can't access a mailbox by using Exchange Web Services (EWS) after the mailbox is moved to Microsoft Exchange Online in Microsoft Office 365 Dedicated/ITAR (vNext). Additionally, you receive error messages that resemble the following: 
  • 401 Unauthorized
  • An internal server error occurred. The operation failed.

Cause

This issue occurs because account credentials aren't accepted in the current format.

Resolution

To resolve this issue, make sure that the user principal name (UPN) of the account's on-premises Active Directory schema is being used during the authentication process. This UPN is the logon for Office 365 Dedicated/ITAR (vNext). Also, this UPN differs from on-premises Exchange or legacy Dedicated/ITAR service that enables the Domain\sAMAccountName attribute to be used.
Properties

Article ID: 3084254 - Last Review: Aug 4, 2015 - Revision: 1

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