Replying to notification emails does not post a message or send the reply to a user in the conversation. To reply to these messages you must go through the website. At times people have replied to these notification emails. To help curb this I setup the sender of notification emails..conversation replies, watched threads, etc as noreply@ww2aircraft.net
So if you reply to these messages within your email client they will be bounced back. Telling you to post reply through website.