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Adding a domain to the Active Directory is something that you don’t do quite often. But with a hybrid environment with Office 365 you may have noticed that you will need to add a new domain to your local Active Directory as well. Now adding a new domain isn’t particularly hard to do, you only need to know where.

In this short article, I will show you how you can add a new domain to your active directory in a few simple steps.

How to add a domain to the Active Directory

1. Login to your domain controller

2. Open the “Active Directory Domains and Trusts”

3. Open the Properties of Active Directory Domains and TrustsRight-click on the top item in the left tree view and select properties

4. Add the new Domain Name

In the UPN Suffixes dialog, enter the new domain name in the “Alternative UPN Suffixes” field and click on Add

5. Apply the settingsClick Apply and close the windows. The domain is now added to the domain controller.

6. (optional) for replication to other domain controllersIf you have multiple domain controllers you can force the replication with the following command in PowerShell / CMD: repadmin /syncall /AdeP

You should now be able to use the new domain name in the Active Directory or in the Exchange Administration Center.


As you can see it’s pretty simple to add a new domain name. Adding a new domain name won’t affect any current users, so you can safely add it, and then make changes to the users accordingly.

If you have Office 365, and use AD Sync, then you will need to add the domain to Office 365 as well. You won’t need to change anything for AD Sync self.

If you have any questions, just drop a comment below.