Outlook, Mailbox, Migration question.

Brass Contributor

Hey Guys, 


So we have a user who is not able to access his mailbox via outlook. But is able to access via OWA. Auto discover fails. 


When checking his office 365 account, he has an E3 license assigned to the mailbox, and when clicking on the mailbox tab the following error comes up: 


"The users on prem mailbox hasn't been migrated to Exchange Online, The Exchange Online mailbox will be available after the migration has completed" 


I checked and the user DOES HAVE the "MSExchangeMailboxGuid" value populated in (our ON Prem) AD, that same GUID is listed in EXO as his "ExchangeGuid". The other recipient types are set as expected (remote mailbox). To be clear the user does have data in his mailbox as well, at over 1GB there are valid and recent emails. 


What I don't get is why OWA works? Also, if i clear his OnPrem MailboxGUID will that cause other problems? Since that same id is currently in use by EXO. 





3 Replies

@Robert Bollinger @TonyRedmond @VasilMichev 


Hey Guy's, Any ideas on this. Hoping you can assist. 



@Robert Bollinger No idea. I'd involve Microsoft support. They can access data in your tenant. I can't.

Thanks for the response. I was more interested in had you seen an issue like this before, where a person has an active mailbox in EXO (Accessible via OWA) but outlook is not able to find the mailbox and the user account is reporting that the mailbox is currently being migrated.

I wasn't asking you to fix it.