Force custom domain validation

[Serty desck]

I need to register a custom domain but there is an error that says the domain has been previously configured on an existing Azure AD or Office 365.  I no longer have access neither I can reset the tenant password because the restore email address is in a domain that i dont own. how can force remove the domain from the other tenant if I am the owner of the domain?

[#2 · Accepted solution]

Contact support, you will have to pass some verifications, but they will be able to help you in this scenario. In addition, check for the so-called "viral signup" issue, where regular users might have "registered" this domain with some O365 service. If this is the case, you as the admin can perform "domain takeover": https://docs.microsoft.com/en-us/azure/active-directory/domains-admin-takeover