title: sendgrid how to track an individual email
body: <p>I am sending emails via sendgrid and would like to track the status of an email.</p>
  
  <pre><code>client = sendgrid.SendGridClient(username_or_apikey=my_key)
  msg = sendgrid.Mail()
  msg.add_to('a@foo.com')
  msg.set_html('&lt;div&gt; hello there &lt;/div&gt;')
  msg.set_from('b@foo.com')
  msg.set_subject('test sendgrid subject')
  resp = client.send(msg)
  </code></pre>
  
  <p>The response object I am getting back is simply <code>(200, '{"message":"success"}')</code>. I was hoping to get back some for of email id.</p>
  
  <p>I know sendgrid has <a href="https://sendgrid.com/docs/API_Reference/Webhooks/event.html" rel="nofollow">webhooks</a>, but how do I associate a <code>sg_message_id</code> with an email that I sent?</p>