Email address points abuse

[Virginia_DS]

Does anyone know how to stop the use of the same email address for customer loyalty points?  Currently, we offer 100 points for the customer to provide an email address, however, the customer can enter the same email address unlimited times and earn unlimited points.

[Candlestore]

Following;

Been trying to setup Loyalty for over a week now, and would like to avoid this situation also.

I have been setting up my Loyalty and I used Options for sizes of my Scents, which created variations, but I cannot assign the Variations heading of 28oz to the loyalty program.  Over 150 different Scents is making this process take forever.