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Multi Domain Office 365 Migration

I have 7 Accepted domains on an Exchange server, 3 of which need to be fully migrated away to Office 365. The main Domain which has the SSL Certificate installed for the DNS names for the OWA, ECP, OAB, outlook anywhere ETC will be staying.
The three other domains will need to be put into the cloud and can't rely on anything from the exchange server once migrated.
I have completed a few single domain cut over migrations and understand the process needed.

Due to the Exchange server having to still serve the other 4 domains I'm at a bit of a loss with what to do.

My suggestion;
Create three new Office 365 portals with the the domain verified
Create an endpoint to the Server (Cut over migration)
Create the Batch, (which will populate all users)
Manually remove any users that don't need to be synced accross
Repeat for the Delta syncs (incremental)
Once the mailboxes have populated and the delta sync has change the DNS Records to that of O365 on the domains, apply the licenses
Remove the batch
Josh C
Josh C
3 Solutions
Vasil Michev (MVP)Commented:
Or just do a Staged migration? Which Exchange server version are you on?
Josh CIT EngineerAuthor Commented:
Staged Migration isn't support for 2010 is it?

Exchange 2010 SP3
Vasil Michev (MVP)Commented:
It isnt, but you havent specified the version so I could only guess. The "express Hybrid" approach is very close to Staged migration though, and is certainly an option you should explore: https://blogs.technet.microsoft.com/exchange/2016/11/28/new-exchange-online-migration-options/

You can configure AAD Connect to sync just the users you want to migrate and proceed. You will still have to perform a cleanup after the migration is done, before you are able to start it against the next tenant.

In theory, you can also work around the Cutover "all or nothing" approach by hiding the objects you dont want to migrate from the GAL, but this will probably create other issues. Another option might be to simply not grant permissions over those mailboxes to the migration account. Or just take the approach you described above - it's doable, though a lot of manual work is involved.

Lastly, there are third party tools you can use, but those cost $$$.
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Jessica KCommented:
Hello Josh,

The migration can be done in three different categories viz. Cutover Migration, Staged Migration, and Hybrid Migration. You can go as per your requirements.
Go through the following forum discussion having a similar query like yours:

Sandeep KumarAssociate ConsultantCommented:
You can use Kernel Migrator for Exchange, one stop solution for all your Exchange, Office 365 and multi domain migration requirements.
For Office 365 Migration refer to https://www.nucleustechnologies.com/exchange-migration/office-365-migration.html
Seth SimmonsSr. Systems AdministratorCommented:
No comment has been added to this question in more than 21 days, so it is now classified as abandoned.

I have recommended this question be closed as follows:

-- Vasil Michev (MVP) (https:#a42361640)
-- Jessica K (https:#a42362214)
-- Sandeep Kumar (https:#a42392452)

If you feel this question should be closed differently, post an objection and the moderators will review all objections and close it as they feel fit. If no one objects, this question will be closed automatically the way described above.

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