@Ronny Forberger thanks for reply!
So, when you delete an Azure tenant, it may take some time for all associated resources, including the domain, to be fully released for reuse. If you encounter an error stating that the domain is already connected to another tenant while trying to link it to a new Azure tenant, follow these steps:
Wait for domain release: Allow some time after deleting the old Azure tenant for the domain to be fully released. This could take several hours or up to 72 hours in certain cases. During this period, the domain is still considered associated with the deleted tenant.
Verify domain status: Confirm that the domain is no longer associated with the old tenant. Perform a WHOIS lookup or contact your domain registrar to check the domain's status and ownership.
Retry domain connection: Once the domain is released and disconnected from the old tenant, attempt to connect it to the new Azure tenant again. In the Azure portal, navigate to the Azure Active Directory section and select "Custom domain names." Follow the steps to add and verify the domain in the new tenant.
- Contact Azure Support: If you've waited an appropriate amount of time, verified the domain's release, and still encounter issues connecting the domain to the new tenant, contact Azure Support for further assistance. They can investigate the domain's status and provide personalized guidance.
Please let us know if further query or issue remains.