title: Check if given email exists
body: <p>Is there a way to know if the email entered by user is real in Firebase? Does the built-in sign up with email&amp;password method have this feature?</p>
  
  <p>EDIT: sorry for the misunderstanding . I don't care if the email has been used before , what I need to know is: if the entered email is 'made-up' or 'real , exists'</p>