After a mailbox is migrated from Microsoft Office 365 legacy Dedicated/ITAR to vNext, you can no longer access the mailbox through Microsoft Outlook. The move request status shows CompletedWithWarning.
The Exchange Mailbox Replication Service (MRS) completed the move but was unable to convert the legacy mailbox into a remote user mailbox. Because the mailbox still exists in legacy dedicated, AutoDiscover does not redirect to vNext as expected.
Article ID: 3188528 - Last Review: Aug 29, 2016 - Revision: 1