This Post will help you on how to create an UPN.
What does UPN stands for ?
UPN stands for User Principal Name.
Why we need to create an UPN?
While configuring ADFS (Federated Service) if we desire to use different domain from our internal domain then we require to create UPN.
Internal Domain Name : SharePoint.local
Desired Federated Domain : SharePoint.com
How to create an UPN Suffix?
It is very simple to create hardly take 2 minute to create one.
Go to DC and search for Active directory domain and trust and open it.
Now, right click on the Active Directory Domain and Trusts. Select Properties.
Enter your UPN suffix you want to create, click ADD and apply,ok to save it.
Happy SharePointing :)