Recently I discovered that a handful of our users had Azure AD UPN’s which differed from their primary SMTP address. This caused confusion for users as they would login to their Microsoft account using [email protected]┬ábut their emails would come from [email protected]

The Azure AD UPN of a user is their Azure AD username. This should match a user’s primary SMTP address and their on-prem AD UPN.

You can safely change the Azure AD UPN after an account has been created without breaking any Microsoft products. End users won’t be logged out of Outlook etc. However, you may need to double check any applications using the Azure AD UPN for SSO.

Prerequisites

Azure AD V2 PowerShell Module

Install-Module AzureAD

Change Azure AD UPN

Connect to Azure AD (this works with MFA). Note: This doesn’t require an elevated PowerShell session.

Connect-AzureAD

Change the Azure AD UPN using the current UPN and desired UPN. The change occurs instantly.

Set-AzureADUser -ObjectId [email protected] -UserPrincipalName [email protected]