[This is more an exim-dev topic]
If there was one agreed hashing mechanism (or probably one defined in
the config of a few selectable), then running a sha*/md* type hash
over the incoming body as it was received would not put much load
on a mail system (especially as mail systems are I/O limited in
almost every case).
Anything cleverer is obviously much harder.
Doing this at any other stage would cause rather more additional
I/O.
Nigel.
--
[ Nigel Metheringham Nigel.Metheringham@??? ]
[ - Comments in this message are my own and not ITO opinion/policy - ]