title: Get Facebook User Email from their FB ID
body: <p>I have spent hours looking for a solution and have finally given up. I'm hoping someone can help me.</p>
  
  <p>Basically, I have an iPhone App where users can sign in with Facebook. When they do this their Facebook ID is sent to the server and is used as their userID (instead of their email, if they sign in with email). Now, if I want to email new users when they register/sign-in for the first time, how can I get the facebook user's email from the ID sent to the server. I do have email permissions from Facebook, but I have no idea how to get the user's email from their ID alone.</p>
  
  <p>Is this possible?</p>