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.
I tested your form and added my email (yahoo mail) and I was able to receive an email and registers in our mail logs.
It could be a problem with your domain so what I suggest you to do is to try to set up a mandrill account and use that to forward emails to your domain.
Also please add jotform's contact email and whitelist our IP https://www.jotform.com/help/145-Whitelisting-JotMails-IP-Addresses