Matthew Rapaport writes:
[...] I don't understand the lure of all these schemes for hiding mail paths, etc.
The disambiguating question is "What is the capability of your opponent?" Some opponents have only access to their own machine as users, and some have access as root. Others have access to all traffic on the local network and can thus see all mail entering and leaving a system. Others, we might assume, have access to all traffic on any non-local network. The rule is the following. If it's cheap enough to defend against even the strongest opponent, deploy it. Cryptography, with its presumably exponential difference between the costs of defense (encryption) and offense (cryptanalysis), allows for economical solutions against even the largest of opponents. Cryptography is a greater leveler than the Colt .45 revolver. Eric