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Ryan Ash's avatar
Ryan Ash
Copper Contributor
Dec 05, 2018
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Changing computer domains when using Azure AD Sync

I have a client that was purchased by another company. (Company A purchased Company B). Both Company A and Company B on their own were using Office 365 and Azure AD Sync. All users and mailboxes from Company B were migrated into Company A's Office tenant. When the merger happened we created a two way transitive AD trust between the two domains. I have removed Azure AD sync from Company B and used Company A's Azure Sync server to sync all the users up to the cloud and this is working and as far as i know how Microsoft recommends it is done when there are two domains in play. Question is this. Company A would like all of the users machines that are still on Company B's domain to be moved over to Company A's domain. I plan to use ADMT for that but that is for a different topic. My question is how can i move a computer that is on Company B's domain and uses Company B's email address over to Company A's domain but keep it synced up with Office 365? I know how to change the sign in name and primary email in 365 from B to A. What i am not sure about is once i have changed the primary email from B to A and also moved the computer form the B domain to the A domain what will happen when the Azure Sync runs and how to make sure the users are still syncing correctly. Also not sure it is relevant but company A uses a Exchange 2013 server in a hybrid setup. Company B does not use any Exchange server. Apologizes if i have left out information.

  • Considering the only thing that really matters to azureAD sync is the users, there should be no affect since you have the domains in the now same tenant. The biggest thing would be if you have any kind of security groups with devices in them you'll need to look that over, but from a 365 perspective, it shouldn't matter, the device is just moving over.

7 Replies

  • I guess the question is, the users from Company B being moved, how are they in Company A? Are they cloud only users or do they exist in Company A's domain?
    • Ryan Ash's avatar
      Ryan Ash
      Copper Contributor

      As of now Company B is all in their own AD domain and Company A is all in their own AD domain.  Part of this process and what the question is, is after users from Company B are moved to Company A's domain, what happens when Azure sync runs?  Since they were being synced from Company B's domain but are now in Company A's domain will they sync correctly and will Office 365 know that it is the same users?

      • You said " All users and mailboxes from Company B were migrated into Company A's Office tenant." can you elaborate, This is what is throwing me off.