Help! Error: The email address is already registered with another account...

I'm seeing the below error when attempting to add the email TIM /at/ ATL /dot/ TV as an alias:

The email address is already registered with another account which is not a part of this organization

However, I nor no one else within my organization has used this domain or email. This seems to be an error. How would I get the other instance of the email removed when I don't have access to that Zoho account?