We completed our migration of all mailboxes to Exchange Online a couple months ago from an on-premise Exchange 2013 deployment. We now need to add new mailboxes for new employees, but we are not able. I suspect that the problem is with the steps that we took to complete the migration process after all mailboxes were moved to the cloud.
For the new employee:
- I've created a new AD account on our domain controller (internal)
- This new account is instantly synched to Office365, showing under our Active Users list with a Status of 'unlicensed'
- There is no mailbox currently listed on our Exchange server's EAC for this new employee. None exists in Exchange Online either (this I know is since he has not yet been assigned a license).
Attempt #1 - If I go ahead and license his account in Office365 Admin Center for Office365 and Exchange Online, a new mailbox is created for him on Exchange Online - however, it is not using the correct domain such as contoso.com (instead - contoso.mail.onmicrosoft.com). I then attempt to add the correct contoso.com address and edit a few other settings, but I am unable to save...the error I get is that settings cannot be changed because users are being synched with on-premise AD and that I need to manage the account from there. If I jump over to my on-premise EAC, there is no mailbox for him there, so I cannot manage him...
Attempt #2 - I went ahead and undid this all, and then attempted to create the new mailbox from my on-premise EAC. After entering the alias and selecting the Existing User, the mailbox failed to create citing an error that no mailbox databases could be reached. Our mailbox databases were actively dismounted after the migration of mailboxes to Exchange Online. To get around the problem, I mounted one mailbox database and then reattempted creating the mailbox...success! Now, I went over to Exchange Online and then after the next synch completed, migrated the new mailbox to Exchange Online (same process as moving the existing mailboxes previously). Once complete, I dismounted the mailbox database on Exchange 2013.
My Question - Does what I'm doing make sense, or did we miss something with the migration to the cloud? From reading on TechNet, our interpretation was that we'd need to always have an on-premise Exchange server to allow us full control over our mailboxes with the EAC that was not available with Exchange Online. This is because our AD remains on-premise and we are not going to move it to the cloud - period. Do we need to maintain a local mailbox database or not? Are there other things we may have done incorrectly in the migration to Exchange Online that are causing this seemingly strange procedure to be required?
Any advise is greatly appreciated!
-Nick