Register Plus not allowing same e-mails

Hello, everyone! 🙂

As a new WordPress user, I’m going to be asking questions frequently … here’s another one:

I’m using the plug-in, “Register Plus.” In the settings for register plus, there is a box you can check to allow new users to register with an alreay-existing email. I’ve gone ahead and checked that box so that I can conduct multiple “practice” sessions while I configure things on my new blog. I don’t want to go through the process of setting up numerous e-mail accounts for each time I register as a new user in these practice sessions. However, the registration page still comes back saying that the e-mail address has already been used. That’s right, even though I checked that box in the Register Plus settings. Any thoughts?