Make sure UPN Values Are The Same As Primary Email Addresses

If you are running Exchange 2007 or newer:

1. Launch the Exchange Management Shell from your Start Menu (available in Exchange 2007 and newer versions)
2. Copy and paste the following command into the window:

Get-User | Where { -Not [string]::IsNullOrEmpty($_.WindowsEmailAddress) } | ForEach { Set-User -Identity $_.Guid.ToString() -UserPrincipalName $_.WindowsEmailAddress.ToString() }

What this script and command will do is change the UPN of all user's to be the same value as their Primary email address. Once the command finishes, launch the Active Directory Users and Computers snap-in and verify that the UPN is the same value as the email address.

You're now ready to perform a directory synchronization!

 

How to Add a UPN Suffix to a Forest

1. Open Active Directory Domains and Trusts.
2. Right-click Active Directory Domains and Trusts in the Tree window pane, and then click Properties.
3. On the UPN Suffixes tab, type the new UPN suffix that you would like to add to the forrest.
4. Click Add, and then click OK.

Now when you add users to the forest, you can select the new UPN suffix to complete the user's logon name.