Hi @Anas IDIR • Thank you for reaching out.
As the tenant is already deleted, you will have to open a Support Ticket to get the custom domain released. If the custom domain is removed prior to the deletion of the tenant, it can be added to the new tenant without any additional steps.
You can raise a support request using Help + support blade in the new tenant. Support team may require you to provide some evidence to prove your ownership to the custom domain by creating MX/TXT record in your public DNS zone. Once validated, they will update the information in the backend and you will be able to add the custom domain in the new tenant.
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