Change UPN of All Microsoft 365 Users

Here’s a useful script you can use when you need to change the UPN and primary email address of all your users in a Microsoft 365 Tenant.

Prerequisites:
- You’ll need the AzureAD.Preview PowerShell module.
- You’ll need to be a Global Administrator of the Azure AD tenant.

Simply change the $NewDomain variable to your new company domain, and change the $OldDomain variable to domain of the user’s you want to change.

Run, and away you go!

$NewDomain = "newdomain.co.uk" 
$OldDomain = "olddomain.co.uk" 
Get-AzureADUser -All $True | Where { $_.UserPrincipalName.ToLower().EndsWith($OldDomain) } |  
ForEach {  
  $newupn = $_.UserPrincipalName.Split("@")[0] + "@" + $NewDomain  
  Write-Host "Changing UPN value from: "$_.UserPrincipalName" to: " $newupn -ForegroundColor Yellow  
  Set-AzureADUser -ObjectId $_.UserPrincipalName  -UserPrincipalName $newupn  
}