I learned something new at this week when was adding domain to O365 environment. Normally process for adding domain is pretty straightforward and shouldn’t take long. Problem arise when domain is already used by your organization and nobody doesn’t know anything about it.
Microsoft has clear instructions how to take over unmanaged tenant. In my case someone had created PowerBI account and during the process tenant was created automatically.
What you need to do:
- Take control of tenant and promote yourself as Global Admin role
- Decide what to do with the affected service and identify users who are using the service
- Remove domain from “unmanaged” tenant
- Add domain to new tenant
Hope this helps!