I am using Entity Forms to create a directory of user submissions. The e-mail field in the form is mandatory. I have a problem where anonymous users are using the same e-mail address to create multiple submissions.

I need rules to check if the e-mail address being submitted is already in the db. If it is I need to block the submission and display a message saying e-mail address already exists in the db.

Can I do this with rules and how.

Thanks