purging redundant segments from {TAIL ~ the mail thread} by analyzing {HEAD ~ the thread identification field} to identify the redundant segments 
purging redundant segments from { TAIL ~ the mail thread } by analyzing { HEAD ~ the thread identification field } to identify the redundant segments
OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH