title: Ae.Net.Mail - IMAP - Get only unseen messages
body: <p>I have a Windows service using the AE.Net.Mail IMAP client with G-mail.  The service runs every x minutes, retrieves inbox messages, applies some business logic, and marks them as deleted. This all works. </p>
  
  <p>However, Gmail leaves them in the inbox so subsequent calls fetch them again. I can skip them by looking at the Seen or Deleted flags but I'd rather not get them at all.  Unless someone goes in and cleans up the inbox frequently fetches will grow exponentially.</p>
  
  <p>I've experimented with Gmails expunge options but they don't seem to have any effect.</p>