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Hybrid Exchange mailbox issue
I am using Online Exchange but I also have a hybrid Exchange 2016 server on prem. Normally, we would will create a new user in on prem AD, add the users mailbox in 2016 and wait for AD Connect to do its thing. They would then be manually migrated to online Exchange.
Last night, one of my team put the user into AD but didnt put the user into 2016 before he went home. Over night we raised the AD forest and domain to 2016 (dont know if this was a contributing factor) and installed CU23 on 2016. The new user was entered into 2016 the next morning and after AD sync, the new user wasnt able to be found in the migration list.
The problem is, for some reason, and it only happened this once, the online mailbox automatically created in Exchange online without the need to migrate it from the 2016 server. We made a new test user and confirmed this was a one off issue as the test user didnt automatically create an online mailbox and showed up waiting to be migrated like normal.
That's a lot to say just to ask is there a way to join the two mailboxes between 2016 and online Exchange? The new user has a USER mailbox on the hybrid 2016 system and a fully functional mailbox in online Exchange but I'd like to link them if possible without removing the online mailbox and starting over.
Thanks
ref link- https://learn.microsoft.com/en-us/exchange/troubleshoot/user-and-shared-mailboxes/mailbox-exists-exo-onpremises
Hello Mark,
unfortunately, you are not able to merge the 2 mailboxes.
If the user has data in the mailboxes (it should be very few, as the user is just created), you should export the content in PST files.
Ideally, by security, I would save on the 2 sides.
Now, the logical way to solve that problem should be to remove the local Exchange mailbox, then using the Powershell command "Enable-remotemailbox" for this user, and force a sync in ADConnect.