[Mailman-Users] Preserving S/MIME-Encoded Mail

Mark Sapiro mark at msapiro.net
Sat Jan 17 03:40:09 CET 2009

Barry Finkel wrote:
>Note that Mailman has taken the existing three-part MIME structure
>(plain-text body, HTML-formatted body, and digital signature) and
>instead of placing the list footer as a fourth part in the same MIME
>structure, Mailman has created a new two-part MIME structure with
>the original three-part MIME structure as a first part and the list
>footer as a second part.
>Is there a reason why Mailman does not place the list footer as a
>fourth section in the existing MIME structure?  Thanks.

Mailman will add msg_header and msg_footer in one of three ways.

1) If the original message is a single text/plain part, Mailman will
attempt to convert the message content and the msg_header and/or
msg_footer to unicode, concatenate them and encode the result back
into the original message character set resulting in a single
text/plain part with the header/footer included. If this fails, go to

2) If the original message is multipart/mixed add the msg_header and/or
msg_footer as additional MIME parts at the beginning and/or end of the
multipart/mixed message.

3) In all other cases, recast the message as multipart/mixed with
msg_header if any as the first part, the entire original message
structure as the next part and msg_footer if any as the last part.

Note that just sticking the header and footer as additional parts into
an original multipart, not_mixed message can't be arbitrarily done.
Clearly, if the original is multipart/alternative, this won't work and
if it is multipart/signed, it would probably break the signature

In any case, the only multipart structure we know for sure we can
safely insert extra parts into is multipart/mixed, so we only do it if
the original is multi-part mixed. If you think this is wrong, I
suggest continuing this thread on Mailman-Developers at python.org.

Mark Sapiro <mark at msapiro.net>        The highway is for gamblers,
San Francisco Bay Area, California    better use your sense - B. Dylan

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