Please note that at least one of the systems under development has an option
where PEM services are applied as a filter, ie. the user feeds in
the message and gets PEM out or feeds PEM in and gets the message out.
So the options are:
Scenario #1: PEM encapsulates MIME
This is, of course, quite allowable as PEM is content independent.
It will be up to the application to "feed" the PEM processed content
to the MIME UA.
Scenario #2: MIME encapsulates PEM
This one is allowable too. MIME (presumably) defines some tags
which identify the next body part as PEM and feeds it to the PEM filter.
The output can then be parsed in any way fashionable. Perhaps it contains
additional MIME and even PEM protected parts. Note that this
is a superset of Scenario of #1 above.
Just for fun please note that this works for other mail systems.
X.400 leaps to mind.
Since the majority of PEM implementors are busy working hard on
their "PEM filters", perhaps the MIME folks should be preparing
to use these filters when they become available. It sounds like
an important 'value added' feature to MIME.
Havin' fun, (BIG smiley)
John Lowry