title: How to listen an MailItem event in Mail Add-in?
body: <p>I want to detect an event in Mail Add-in. In Outlook, thick/desktop version, we can detect the mail event, such as <code>MailItem.Send</code> and <code>MailItem.AttachmentAdd.</code></p>
  
  <p>Is it possible to listen to these events in Outlook online?</p>