We are in the middle of hybrid coexistence migration from Exchange 2010 on-premise to Office 365. That means we have ADFS and "Dirsync" (now called Windows Azure AD Sync) running. We are more than halfway through migrating mailbox, so about 60% of our users' mailboxes are in the cloud and the remaining 40% or so are still in on-premise Exchange 2010 databases.
Today we discovered that one of our users has both an on-premise and an Office 365 mailbox linked to his one AD account. That means that if he opens Outlook on a domain-joined computer and goes through the initial configuration, it uses autodiscover to connect him to his on-premise mailbox, but if he logs on to the Office 365 portal, it shows his cloud mailbox.
Even worse, when a user whose mailbox is in the cloud sends him an e-mail, it goes only to his cloud mailbox, and when a user whose mailbox is still on-premise, it goes only to his on-premise mailbox. So he can't see all his mail all in one place.
How can we "merge" his mail data (final destination: Office 365) and make sure his Outlook "autodiscovers" the Office 365 mailbox and all mail is routed to that mailbox?
Best Answer
I've the same problem in my domain. Someone manually create the o365 mailbox for users who already have an on-premise mailbox
I've found this way to fix it:
Remove-MsolUser -UserPrincipalName youruser@youroffice365domain.com -ForceRemove-MsolUser -UserPrincipalName youruser@youroffice365domain.com -RemoveFromRecycleBin -ForceI think is more simple and straightforward. You can also re-migrate your mailbox on-prem (offboarding) if you need it.