Rather than reject users because the domain is not valid send to an approval process Merged

The self-registration feature in Portals is nice.  But the "safe" domains can create some management overhead and unnecessary calls.  If the domain doesn't exist then rather than say Your email domain doesn't allow you to self register

Have an option to send an email to a defined admin user who can approve the usage.  On approval the user attempting to sign-up will receive an email informing them they have been approved.  It'll cut down on the back and forwards if you have 100 of client domains you need to register.