[Wired1]

Originally Posted by Alfa1

A system could be used that when an email domain is submitted by more than X vbulletin sites, the domain is marked as a temporary/fake email.

That would block sites like gmail, yahoo, hotmail, etc.

Now keeping track of sites w/ throwaway email addresses and/or super secret ones (e.g. hushmail, etc) might not be a bad idea. Could give admins the option to block registration based upon having an email address from one of those sites, and use a custom phrase for the denied reason (e.g. "You are attempting to register with a temporary email address. We require that our members use real email addresses so that if we need to contact them we can."