This is a port of an addon I made for vBulletin back in September of 2014
The settings for the mod can be found under, [OzzModz] Block Registrations With Spam Like Email Addresses
Note: The error message they see when they exceed the maximum dots is this:
"The administrator has blocked the email you have entered for containing to many special characters. Please try a different email address."
I would not suggest changing it and saying something like, " you entered to many dots " or some such as this will just tip the spammers off.