A cloud-based identity and access management service for securing user authentication and resource access
The domain is already verified in another Microsoft 365/Entra tenant. A custom domain can only exist in one tenant at a time, so it cannot be added or verified again until it is removed from the old tenant.
Because there are no credentials for the old tenant, self-service removal is not possible. The only supported options are:
- If anyone in the organization might still have admin access to the old tenant
- An admin of that tenant must sign in to the Microsoft 365 or Entra admin center and remove the custom domain from that tenant.
- After the domain is removed there, it can be added and verified in the new tenant.
- If no one has access or the tenant is unknown
- This is treated as a “domain exists in another organization” / “unknown tenant” case.
- Contact Microsoft support and request help to move or release the domain from the unknown tenant. Be prepared to prove domain ownership (for example, by adding DNS records that support asks for).
Key points from the documented behavior:
- Error messages such as “<DomainName> has already been verified for your account, or for another Microsoft Online Services account” or “Can't verify the domain <DomainName> was already added to a different Office 365 account … remove domain <DomainName> and then try again” indicate the domain is in another tenant and must be removed there first.
- If the old tenant cannot be accessed and its details are unknown, only Microsoft support can assist after validating ownership.
Until the domain is removed from the old tenant (by an admin of that tenant or via Microsoft support after verification), it will not be possible to add and verify the TXT record for that domain in the new Entra ID tenant.
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