Move onmicrosoft.com subdomain

Hello Marco C,

The *.onmicrosoft.com domain (for example, co2cause.onmicrosoft.com) is the initial tenant domain and cannot be moved, renamed, or transferred to another Microsoft Entra tenant. This is a platform limitation and is not supported by Microsoft.

Supported solution steps:

1. Leave co2cause.onmicrosoft.com in the original tenant The onmicrosoft.com domain will remain permanently associated with tenant 322b246c-***********.
2. Use co2cause.com in the target tenant Ensure co2cause.com is fully removed from the source tenant and then added and verified in the fznatural.onmicrosoft.com tenant.
3. Set co2cause.com as the primary domain In the target tenant, set co2cause.com as the primary domain so users sign in as ******@co2cause.com.
4. Update users and services Update user UPNs, mail addresses, and application configurations to use @co2cause.com.
5. Optional (fallback domain) If needed, you may add a new available onmicrosoft.com domain to the target tenant, but an existing one from another tenant cannot be reused. Final clarification:

While co2cause.onmicrosoft.com cannot be moved, all production identity and branding should rely on co2cause.com, which is the supported and recommended design.

The onmicrosoft.com domain that’s created with a tenant (such as co2cause.onmicrosoft.com or fznatural.onmicrosoft.com) is permanently bound to the tenant where it was created and cannot be moved or reassigned to another tenant.

What can be done instead is:

1. Keep using co2cause.com as the primary/custom domain in the target tenant (where it is already verified and in use).
2. Ignore the co2cause.onmicrosoft.com name in the old tenant; it does not affect use of co2cause.com in the new tenant.
3. If the old tenant is no longer needed, remove any custom domains from it and decommission that tenant according to organizational and subscription requirements. The initial *.onmicrosoft.com name in that tenant will remain there but has no impact on other tenants.

There is no supported method to:

• Move co2cause.onmicrosoft.com from tenant 322b246c-0a3d-4adc-afa5-b9d09eb57d50 to the fznatural.onmicrosoft.com tenant, or
• Rename the initial fznatural.onmicrosoft.com tenant domain to co2cause.onmicrosoft.com.

To present co2cause.com to users and applications, continue to use it as a custom domain in the fznatural.onmicrosoft.com tenant and set it as primary for user UPNs and email addresses.

References:

• Add your custom domain name to your tenant