The mailing list for listmasters using Sympa

[address@concealed (Kendall Libby)]

We recently had a user complaint that cerain lists had recently
(i.e. "some time in the past few months") started to strip images out
of distributed messages.  The missing images were all inline, as part
of a MIME multipart message.  They show up in the archives but were
not included in the message delivered to list members.

As it turns out, it's been doing that for much longer.  Except not
always.  Very confusing.


The users all have html reception mode set, and it appears that Sympa
is forcing the multipart message down to a single part and ignoring
the images that are in the html message.  That would make sense to be
for text/plain, but seems a bit heavy handed for text/html.  Should
Sympa really do that?  Or to put it a different way, how difficult is
it to determine which MIME parts should be kept for "html-only"
messages? 


Unfortunately, I suspect it's not an easy solution.  As I said, I've
found cases where messages were NOT stripped of their images.  The
only significant difference I see is in the MIME headers, but it's not
clear why they're different (it may be an Outlook vs Exchange thing).


For example, the message with stripped images originally had:

> Content-Type: multipart/related;
>         boundary="----_=_NextPart_001_01CA71CB.299C8ECA";
>         type="multipart/alternative"

...which was changed to:

> Content-type: text/html; charset=us-ascii


The message without stripped images has:

> Content-type: multipart/related;
>  boundary="----=_NextPart_000_00C1_01CA6D00.DFCD9420"

...and was unchanged by Sympa.  All of the MIME parts in the message
are missing the 'type="..."' label.  


If I set a user to 'mail' reception mode, the messages aren't changed
and the images come through normally, so we have a workaround.  But as
I say, stripping relevant MIME parts from a text/html message seems a
bit heavy handed.


(we're seeing this in 5.3.4, but the relevant code is the same in
 6.0.1.  I'll have 6.0.1 running in the next week or two and will
 test it there.)

K.