We are not able to receive the notification e-mails, what should be do to resolve this issue??

The email address used for submission notifications is not in our bounce list, have you checked spam folder? 

If the issue continues you need to white-list our Jotmail IP addresses within your email server (or ask for it to your email service provider). Read this article for more details: http://www.jotform.com/help/145-Whitelisting-JotMails-IP-Addresses