displaying, on a display screen, the single message document according to a conversational view based upon {TAIL ~ a perspective} of {HEAD ~ the response level} of a user within the mail thread 
displaying , on a display screen , the single message document according to a conversational view based upon { TAIL ~ a perspective } of { HEAD ~ the response level } of a user within the mail thread
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH