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I have checked the log for the email address you're using in your form http://www.jotform.us/form/51766541425154 and I can see there are some failed emails; however, seems like emails are being sent now and I tested your form and can confirm this, here is a screenshot of the email successfully sent upon my submission:
Please do confirm us that you're receiving emails now.
Also, when I was checking your form I found that there is some missing info such as "Sender Name", please do note that some email providers will not accept emails with missing info, this is why I would suggest you to check this guide about How-to-Prevent-Email-Bouncing-Related-Issues
And if you suddenly stop receiving emails again, please check if the email address you're using is not in our bounce list, this is one of the reasons why emails do not send, here is the link to the guide: How-to-Remove-Your-Email-Address-from-Bounce-List
In case that the issue still persists, please ask your email provider to white-list our IP addresses, you will find all our mail server info here: Whitelisting-JotMails-IP-Addresses
Hope this helps.