Error when attempting to delete *.onmicrosoft.com domain from my tenant

Question

I'm trying to delete an *.onmicrosoft.com domain from my tenant and have followed these instructions: https://learn.microsoft.com/en-us/microsoft-365/troubleshoot/sign-in/unable-remove-domain-office-365 to confirm that:

1. there are no user names in that domain
2. There are no email addresses with that domain

When I go to the Azure portal: https://portal.azure.com/#view/Microsoft_AAD_IAM/DeleteDomainBladeV2/domainName/<mydomain>.onmicrosoft.com it shows me three ticks under Meets requirement? When I then click Delete I get this error:

Unable to delete domain name <domain>.onmicrosoft.com from <companyname>

Request Id: cf2cc60f-1e0b-40c1-825f-1f34bfb89db1
Time Stamp UTC: 2022-12-20T08:50:47
Code: Request_BadRequest
Message: Domain deletion attempt failed.

This domain used to be the fallback domain for my tenant, but I changed the fallback domain to a different *.onmicrosoft.com domain.

Answer 1

@Craig W. Mischenko

You cannot remove the initial .onmicrosoft.com domain that was created while tenant creation.

Microsoft 365 needs to keep it around because it's used behind the scenes for your subscription. But you don't have to use the domain yourself after you've added a custom domain. If you choose to create a new onmicrosoft.com domain, it cannot be removed. You are limited to five onmicrosoft.com domains in your Microsoft 365 environment, so make sure to check for spelling and to assess your need if you choose to create a new one.

You can also refer below article which is publicly documented.

https://learn.microsoft.com/en-us/microsoft-365/admin/setup/domains-faq?view=o365-worldwide#why-do-i-have-an--onmicrosoft-com--domain

Do let me know if you have any further questions.

Please "Accept the answer" if the information helped you. This will help us and others in the community as well.

Answer 2

You cannot remove the original .onmicrosoft.com domain, it's still used by parts of the service even if you have added a new one.