I can create a new customer and hosting spaces without issue. The issue is the new email addresses cannot receive emails from outside the server. The new domain can email each other. The other domains on the server can send and receive email to this domain. But anything from outside, Hotmail, gmail etc fail with:

Remote Server returned ‘550 5.1.10 RESOLVER.ADR.RecipientNotFound; Recipient not found by SMTP address lookup’

Answered question