Only allow 1 submission from an email address in webform I am taking some users information using webform, which is their name and email address.

I need to only allow one submission per email address, restricting the form by IP or cookie in the webform settings is not sufficient in this case.

Is this possible?
Edit the email field in the webform and check both the "mandatory" and "unique" options. 

In this case, it would accept entries only for unique mail id's