On Fri, 22 Sep 2000 [log in to unmask] wrote:

+ Note that technically, it's *very* hard to delete a bodypart *and* insert
+ a notation into the *body* and have it Do The Right Thing.  Placing the
+ text before the first part or after the last part will probably be invisible
+ to a MIME-aware mail program (that's where a lot of things put their
+ "This message is in MIME format - if you see this text, consider upgrading"
+ warnings).

Yep. That's one of the reasons I have exmh set to always show that
pre-amble ;-)

+ Putting it into an existing bodypart is dangerous - it may not even be
+ a text/plain (users may object to their spreadsheet being corrupted by
+ insertion of arbitrary data.  Or it may be a multipart/signed like this
+ one, where insertion of data may result in invalidating a digital signature.

Also true (and especially the multipart/signed part but that's a
completely different story ;-). However, the basic assumption with both
the attachment removal and optionally adding a small note in what could be
called the 'main message' (practically speaking (at least according to the
way most user agents treat a MIME-message) the first text/plain
part, if any) is that on behalf of the list-owner the message is modified
anyway. Whether that is by adding a short trailer or by adding a note
about a completely removed body part is more or less the same. A list
owner shouldn't even think about options that modify the bodyparts when it
is expected and encouraged to send digitally signed messages for example.

In the case the list-owner decides to 'modify' the message all
transparency-assumptions (what goes in must come out) disappear. The list
has become something where you send mail to and on the other side
something completely different appears (which by all means can be a good
thing, it just isn't transparent and one has to be carefull about
what is being sent to such a list).

And in that case I prefer to know (as a recipient) that the message has
been modified. With trailers that is obvious, with the removal of
body-parts (attachment-stripping) but passing the stripped message that's
not obvious (current implementation).

+ ON the other hand, I'd welcome Listserv adding a header to the main
+ RFC822 headers of the form:
+
+ X-Modified: A application/whatever of NN,NNN bytes was removed by listserv@NODE
+
+ or some similar.

This has the same dis-advantage as putting a note in the pre-amble, most
if not all user agents don't show these headers by default and the
recipient has to do some work to see them, many of them won't even bother
I guess.

Anyway, given the fact that there is an option to remove selected
body-parts and someone one day might decide to add a warning somewhere I
would prefer either the Pine-method (replacing the parts with a text/plain
body part with the note) or putting them in the first text/plain (and if
there isn't one, create one). The result is in both cases a completely
different message and care should be taken that the outcome is still a
valid MIME-structure but of course that was the intention of the
attachment stripping anyway ;-)

Xander