title: IMAP flags always has :Seen flag
body: <p>I am importing emails into an application using imap:</p>
  
  <p>I have the following code:</p>
  
  <pre><code>since_time = Net::IMAP.format_date sync_time
  
  google.email.all folder: folder, keys: [ 'SINCE', since_time ] do |mail, imap, uid|
    flags = imap.uid_fetch(uid, ['FLAGS'])[0].attr['FLAGS']
  
    if flags.include?(:Seen)
      #flags always has :Seen
  </code></pre>
  
  <p>I want to mark emails as unread if they have not been read but using the code above, the :Seen flag is always returned.</p>
  
  <p>My understanding was that the :Seen flag is only returned if the email has been marked as read.</p>
  
  <p>Am I misunderstanding how the flags should work?</p>