https://learn.microsoft.com/en-us/answers/questions/563790/adding-a-custom-domain-after-creating-users
Adding a custom domain after creating users - Microsoft Q&A
Hi all, I have an Office 365 E3 instance that was set up by someone else. Unfortunately, we have created users with the default domain name (e.g....
adding a custom domaincreating usersmicrosoftq