I was speaking to a customer today about a project so help them move to Azure.
Step 1 is to setup their AD Connect and Hybrid Identity.
The first thing they said “Can we change our domain name?”
Their domain name was similar to testtenant.onmicrosoft.com **This was not their actual domain name**
So there are probably a few tenants named like this. People start setting things up in Office 365 etc and just pick a random domain name, as those things can always be changed later, right?
Wrong! The initial domain name choice is really important. It cannot be changed. If you need to change it at a later date, then you will need to setup a new Office 365 subscription. If you’ve already setup things in the original tenant then you’ll need to redo them in the new one. There are migration methods available – but you’ll be heading into a whole world of pain!
There is a Uservoice created back in 2016, but despite promises from Microsoft, there is still no solution.
This article describes what the onmicrosoft.com domain name is for, and also shows the following:
You can’t rename the onmicrosoft domain after sign-up. For example, if the initial domain you chose was fourthcoffee.onmicrosoft.com, you can’t change it to be fabrikam.onmicrosoft.com. To use a different onmicrosoft.com domain, you’d have to start a new subscription with Office 365.
You can add custom domain names to your tenant, but that’s a different blog for a different day.
Moral of the story:
Pick your initial domain name carefully!