{HEAD ~ An incoming message} is intercepted at {TAIL ~ a network domain boundary} and assigning a unique filename 
{ HEAD ~ An incoming message } is intercepted at { TAIL ~ a network domain boundary } and assigning a unique filename
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH