One of the projects I’ve been involved in took over a year for a decision to be made on the custom domain that will be used for user accounts and the services that will be offered. This meant that all the accounts used the @somecompany.onmicrosoft.com domain for a year during development and when the time came to register and use the new domain, there was already hundreds of accounts. Using the portal.azure.com GUI wasn’t practical given the amount of accounts so I wrote a PowerShell script to update the accounts. The script can be found at my GitHub repo here: https://github.com/terenceluk/Azure/blob/main/PowerShell/Update-Azure-AD-UPN-Domain.ps1
