A user registered with my WordPress blog as "[email protected]" (for example).
I'm fine with that. However, if the user comes back with "[email protected]", I want to stop him for registering again, and maybe politely remind him that he's already registered with the "same" gmail address.
Is there a plugin that does this?
I realize people can easily get free no-registration-required email addresses, so this won't stop someone from registering multiple times, but it might help.