Clicking on message generate two requests:
"GET /?_task=mail&_action=preview&_uid=414&_mbox=Spam&_framed=1 HTTP/1.1" 304 26 "POST /?_task=mail&_action=mark HTTP/1.1" 200 205
and one login to imap server for each. I think such "related actions" should be done with one imap connection and one request.