Received Notification

I recently get ordered to review user email and I noticed when I open an email(can’t remember which one) it send user notification from me that I had received. I checked his mail design but did not see any agent that stand out. I could not make out how this setup or what to do to get around it. Anyone have any suggestion?User running on 5.0.8 client

Server are on 6.0.3

Subject: Received Notification

This is not an agent… it’s a Delivery Option that the sender chose when he sent the email.