To delete a domain:
Go to entra and look for Custom domain names under the Manage section. Click on it to view the list of domains associated with your tenant.
Ensure that the domain you want to delete is not being used as a primary domain or assigned to any users, groups, or applications. If it is, you’ll need to remove any associations first.
Before deleting a custom domain, you must make sure the following:
- Remove any user with a username, email address, or proxy address using the custom domain name
- Remove any group which has an email address or proxy address using the custom domain name
- Remove any application in your Azure AD that uses the custom domain name
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Regards,
Abiola