To and From addresses interchanged - Incoming mail found in Sent box

brucebow

Honorable
Jul 10, 2013
3
0
10,510
An incoming email has found its way into my sent box. It is a crisp reply to an email that I sent. The reply quotes a line from my email and adds a comment about the quoted line. The major query concerns the to and from addresses. The header indicates that I sent the reply to the guy who emailed me - but I was the receiver not the sender. How could the addresses have been switched around?
 

brucebow

Honorable
Jul 10, 2013
3
0
10,510