UPN Suffixes and Domain Names

The User Principal Name (UPN) is the username in "email format" for use in Windows Active Directory (AD). The user's personal username is separated from a domain name by the "@" sign.

UPN suffixes are part of AD logon names. For example, if the logon name is administrator@ad.example.com, the part of the name to the right of the ampersand is known as the UPN suffix. In this case, ad.example.com

When you configure a new user account in AD, you are given the option to select a UPN suffix, which by default will be the DNS name for your AD domain. It can be useful to have a selection of UPN suffixes available. If your AD domain name is ad.example.com, it might be more convenient to assign users a UPN suffix of example.com. To make additional UPN suffixes available, you need to add them to AD.