Does the userPrincipalName (UPN) attribute always exist in Active Directory?

Solution 1:

The User-Principal-Name attribute is only used within the User class. Note that the attribute is not marked mandatory.

The following Powershell example will create an AD user without a UPN:

Import-Module ActiveDirectory
New-ADUser -Name abUser

Observe that there is no UPN defined on the user object:

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