What is JotForm?
JotForm is a free online form builder which helps you create online forms without writing a single line of code. No sign-up required.
At JotForm, we want to make sure that you’re getting the online form builder help that you need. Our friendly customer support team is available 24/7.
We believe that if one user has a question, there could be more users who may have the same question. This is why many of our support forum threads are public and available to be searched and viewed. If you’d like help immediately, feel free to search for a similar question, or submit your question or concern.
Yes that is possible to achieve.
You can take advantage of our "Unique Question" feature and you can limit your form. One you set your form's email field as a unique question, multiple submission using the same email address will not be allowed.
Here is a guide which should help you: http://www.jotform.com/help/223-How-to-set-Form-Limits-Based-on-a-Unique-Question
Hope this helps.
Do get back to us if you have any questions.