Office 365 Migration – Adding Additional UPNs

In my previous post office-365-migration-user-attribute-discovery-export-powershell/ I described the importance of matching your user UPN with their primary SMTP Address.

A scenario I recently came across was where the customer didnt have the correct UPN Suffix registered in their Active Directory Forest.

For example, the root domain was so all their UPNs were similar to [email protected]. They also had some users with a Primary SMTP Address of but their UPN was still

Can I add a UPN to my Forest? Will it destroy things?

Yes. No. The default UPN is created when you birth your Active Directory and it matches the FQDN. Your users can log into domain resources with either their UPN or their SamAccountName. UPN suffixes can be added, by Powershell or the Active Directory Domains and Trusts Snapin.

Adding a UPN Suffix is primarily performed, but not restricted to (see above scenario), for non routable domains (Good MS post here on them) e.g. your domain is contoso.local but you want users to log into resource with [email protected] because your verified Office 365 domain is In this scenario you would add as a new UPN Suffix in your Active Directory Forest

How do I add a UPN Suffix?

What do we need to do. Lets assume you have no additional UPN Suffixes and want to add The account you use for the following commands requires either “Domain Admin” or “Enterprise Admins” membership. Read More

This cmdlet will bring back your current Domain name (and UPN Suffix)

Will return nothing. Lets add as a UPN suffix to our Active Directory Forest

Did it work? Lets see. Run the Get-ADForest cmdlet again

All things being well you should see your new UPN Suffix listed.

How do I assign the new UPN Suffix to my users?

The new UPN suffix will be available in the Active Directory Users and Computers Snapin. Edit the user and navigate to the Account tab. The “User Logon Name” is the UPN prefix. The drop down box lists the UPN Suffixes available”. You should see your new UPN Suffix here.

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