Exchange resource forest migration to O365

[woelki]

Hey guys,

I've found here a lot of cross forest and multi forest questions, but they do not fit to my question.

A customer of us has a "classical" cross forest scenario with an account forest and an resource forest.

So user accounts are in forest A and mailboxes are located on Exchange 2010 in forest B.

I often heard in the past, that it would be necessary to move the mailboxes to forest A before I can migrate them in a hybrid deployment to O365.

Currently we have AAD connect setup in forest A and starting to deploy an Exchange 2013 server as hybrid server in forest B.

Is there anything else we have to consider when moving our "linked" mailboxes to O365?

Kind regards,

woelki

[#2]

@woelki I've been working on similar migrations for two of my customers. The migration of linked mailboxes works fine. I know it wasn't supported for a while, but I've not been able to find anything current that says it is unsupported. The only thing I would recommend is making sure your AAD Connect is matching the two accounts correctly and only creating the one account in Office 365. This was the task that took the longest. Configuring AAD Connect to match on SamAccountName and to use the msDSConsistencyGUID seemed to work well (as long as your accounts have the same SamAccountName's in the account and resource forests).

The fun bit comes if you want to decommission the resource forest!

Dan

[#3]

MVP fellow Jaap Wesselius did a short series on migrating to Office 365 from a resource forest deployment, which might be helpful in your journey:
https://jaapwesselius.com/2018/04/26/exchange-resource-forest-and-office-365-part-ii/