How to I registrate the email-account that is receiver in a contactform?

I'm afraid that I couldn't complete understand your question.

If you are asking about sending email notifications from your form to an email address that is not registered for a JotForm account, you can certainly do that - recipient of email notifications doesn't need to be registered.

When setting up your email notification, simply enter your desired address in the Recipient Email field.

If you are instead asking how you can register a new JotForm account with a different email address, anyone can signup for a free JotForm account over our signup page:

https://www.jotform.com/signup

Please let us know if you need any clarifications, or kindly clarify a little more if you were asking about something else, and we will be happy to help.