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Merging/migrating domains to one domain

I have a client who just got bought out by another company.  Company A has a 2003 dc and exchange 2007 (two separate servers), as well as a sql server and a couple of citrix servers.  Company B (the company who bought the other) has a 2008 r2 dc (in fact they have 2 2008 r2 dc's) and an exchange 2007 (which was a dc, but we moved the roles off of it and demoted it to a member server).
We need to merge the two domains to the Company B domain.  Ultimately all users would log into the Company B domain, users who were in Company A would still retain their Company A email, but users from Company B should be able to view Company A user calendars and other shared resources.
Company A needs to be able to function as normal but under the Company B domain.  I'm probably not doing  a good job of describing this but ask me any questions and I'll do my best to answer them.
So my question is how do I do this? What's the logical process and is the process documented anywhere?  Thank you in advance...
Active DirectoryWindows Server 2008Exchange

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Edward Gutman

8/22/2022 - Mon
Edward Gutman


what you should decide at this point is if you are only interested in the emails or the whole Company A current setup (i.e. user profiles, permissions etc...)

Assuming you want to keep the whole things and not just email you will need to use ADMT to migrate users group and computers to the new domain/forest then the move-mailbox cmdlet to move the mailboxes.


Hello guys,

Thanks for the reply... I apologize for taking so long with mine.  At this point we are definitely looking at moving over the entire company and merging Company A into Company B.  When using the ADMT tool, what happens to Company A dc's?  Is this domain still active? Or does ADMT tool only remove the users and computers from Company A's domain.  Thanks again for your help...
Your help has saved me hundreds of hours of internet surfing.
Edward Gutman

The domain controllers remain online throughout an ADMT migration.   After you have completed the migration of all users and member computers, you can demote the DC's for Company A to member servers.  Then you can move them to Company B's domain as member servers.  If you wish, you can then promote them to DCs for Company B's domain.  After your demote the last DC of Company A's domain, that AD structure no longer exists.

Thank you!!!  Is there a way to keep Company A's exchange server active during this process?  Meaning having it still functional without moving the mailboxes to Company B's exchange server?  Would it be possible to have both exchange servers up and running under the Company B domain?  Or is it the smarter choice to move all users to Company B's exchange server and scrap Company A's exchange server.  Also how will the ADMT tool effect Company A's exchange server?  Thanks again...
Edward Gutman

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