User Banned?
 

A lot of new users on my forum are recieving a message like:

Quote:
The administrator has banned your email address. To contact the administrator click here
Upon registration.
At first I thought this was an issue with the plugin that I was using, but that has since been disabled and then uninstalled, and the same problem still occurs.
I've also checked my list of banned emails, and the emails they are using (mostly yahoo/hotmail/aim) are not listed under my banned email domains (Aggressive banning is also off).

So i'm slightly stumped as to what's going on here.

Anyone think they can help?