Office365 migration mixed domain accounts

VasilMichev 

Thank you for the response, nice response

I assume that internal takeover is not an option, because if we delete customer3.es domain from the other account, users will became mailto:user1@customer3.onmicrosoft.com and this is not a possible option

If you have any users or groups in Microsoft 365 that reference the removed domain name, they must be renamed to the .onmicrosoft.com domain. If you force delete the domain name, all users are automatically renamed, in this example to user@fourthcoffeexyz.onmicrosoft.com.

So i think that the only option is to force domain takeover to the correct account, right?

Two questions if we do a force takeover

  1. Existing @customer3.es users, will still be able to log in using its mail to power BI and other services?

  2. In our account, we will be able to see which affiliate users have signed in with auto services like power BI free, right? For legal purposes, customer doesn´t want to see which affiliate users that use @customer3.es accounts have signed in other o365 services, is there a way to do this?

Thanks a lot for the response