{TAIL ~ the external storage} is polled by the second application for {HEAD ~ the presence} of an encrypted electronic message, 
{ TAIL ~ the external storage } is polled by the second application for { HEAD ~ the presence } of an encrypted electronic message ,
TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH