User registration with default acme template

Hi, I use your wonderfull plugin. But for about two weeks now I get spam registrations, which have the default green acme template used. All Email send by the page use my own made design. I don’t show a registration page for our customers, they can only register while buying something in the cart. You can only login with an existing account. Also if a customer registers with the checkout, he will get the own design of course. Any ideas how that would work out?

Thx in advance