logging in with an email adress

Are you looking to create login forms? Unfortunately, we do not allow it, that goes against our terms of use: https://www.jotform.com/help/8-Terms-of-Use 

"Phishing. You agree that Company may terminate your JotForm Service immediately if a form's purpose is found to be deceptively obtaining: sensitive credit card information, social security numbers, user login credentials, or other sensitive personal information. All these activities are considered as Phishing and any account along with the violating forms will be suspended immediately."

If that is not what you mean, please provide more details of what you need to accomplish, we will be glad to assist you.