Can't validate my email because domain does not exist anymore

[jerdog]

This would be the process you should follow:

Change account email address

You can go to your tenant settings, navigate to the Dashboard Admins section and just add a new email address as an administrator for All Applications. Having completed this process for the tenants in question and verifying that the new administrator can authenticate and manage the tenant succesfully you can then consider removing the other administrator entry.

Let me know if that does/doesn’t work for you.