merging non redundant segments of the each of the related e mail messages into a single message document by ordering the non redundant segments hierarchically by the response level and the mail timestamp of {HEAD ~ the each} of {TAIL ~ the related e mail messages} 
merging non redundant segments of the each of the related e mail messages into a single message document by ordering the non redundant segments hierarchically by the response level and the mail timestamp of { HEAD ~ the each } of { TAIL ~ the related e mail messages }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL