title: Email client detection
body: <p>I have a project to send some email to end clients. My client need to know what exactly "Email Client" they use to read the mail. I know a hidden  can get the open event and even the user agent they use, so by parsing user agent i can get most email clients info.</p>
  
  <p>But it's hard to detect some popular web mail clients like "Gmail", "Hotmail" and "Yahoo mail". Because user agent return is only the browser user agent string.</p>
  
  <p>Edit: i think i need a result more like this:
  <a href="http://fingerprintapp.com/email-client-stats" rel="noreferrer">here</a></p>