Thanks Ned for your X.4xx review here.
I agree, when it comes to gateway transformations lacking a 1 to 1
map, there are things that require a design decision. Sometimes you
have no choice but to follow the side, the rules, of the end-gate.
So what does all this mean? It means that if you gateway to a pure X.400
environment that rigorously follows all the rules and uses P7 to talk to
you end up with more or less the operational behavior Keith wants,
defaults may be to auto-discard. (I didn't find a default in the standard
itself, which means it's probably operational-profile-specific.)
you're dealing with a real-world implementation that doesn't use P7 or
operates with an Internet rather than X.400 kant, you're not going to have
per-user controls for this and you're likely to see such messages discarded
automatically with no recourse.
I will also note that while we don't support X.400 any more, since the
expiry-date check was implemented at the MTA level it is actually
still support doing. Of course I have no idea if anybody actually have the
feature enabled any more - I suspect not but there's no way to be sure.