In addition, if I put in the same email twice I get a message that the email is not valid.
There is one other thing. In order to try it I had to use a different e-mail address each time or I would get the error:
Failure Oops, there was a problem adding your information. Make sure you entered a valid email address.
Users that are subscribing may not understand that the e-mail address is a dup. In my point of view it would be better to just accept the duplicate and thank them .