Currently there's nothing stopping customers from adding domains such as gmail.com, paypal.com or even our own company name to their control panel. With this they can alter DNS or setup mail accounts for local delivery.
It would be great if we can create a list of blacklisted domains that cannot be added to Enhance globally.
We could probably add the domains ourselves as accounts and change the mail settings but this isn't an ideal solution and a simple blacklist would be a much better method.