How to do it...

UPN suffixes can be managed using Active Directory Domains and Trusts.

To do so, perform the following steps:

1. Open Active Directory Domains and Trusts (domain.msc).
2. Right-click Active Directory Domains and Trusts in the left navigation pane, and select Properties from the context menu:

1. Type the new UPN suffix that you would like to add to the Active Directory forest, select the UPN suffix that you would like to remove, or simply glance over the list of UPN suffixes.
2. Click Add or Remove, and then click OK.