Adding a Subdomain Problem

[ErikVet]

Hello,

we have problem adding a subdomain to our environment. It is a ADFS enviroment and we have added the Domain always via PowerShell  -> New-MsolFederatedDomain.

If we add a specific subdomain we get the following error. 

Any other subdomain within the root domain works without any problems. 

What does this mean, has somebody setup a O365 environment and this is an unmanaged azuread with this subdomain and do we have to do an admin takeover ? We have found some blog posts about this. 

Many Greetings

Erik 

[#2 · Accepted solution]

Reply to myself ;) it is correct, if you have to make an admin takeover as described here. https://docs.microsoft.com/en-us/azure/active-directory/enterprise-users/domains-admin-takeover This works without any problems. Many Greetings Erik