title: IMAP and Flags.SEEN
body: <p>One way of ensuring an IMAP client is in sync with its server is to leverage the SEEN flag (e.g., <a href="https://stackoverflow.com/questions/11362542/library-for-imap-idle">Library for IMAP IDLE</a>).  </p>
  
  <p>I have not yet used this myself, but I was wondering if setting the SEEN flag basically sets the message to "read" on the server. </p>
  
  <p>If so, this is obviously a problem when there are multiple readers involved or when the user logs into the server directly (e.g., logs into their Gmail account) and reads the message there (so that it is "marked read", and - thus - flagged as SEEN).</p>
  
  <p>Or, I could be misunderstanding this completely and SEEN is something that is unique between a particular client and the server.  However, not clear how to maintain state in that case.</p>