[Mailman-Users] Reply Bodies as Attachments

[Stephen J. Turnbull]

rex at rexgoode.com writes:
 > I'm having the same problem on all of my lists, which most people read 
 > on their Android or IOS devices.
 > 
 > When I send something out, if anyone replies, it is delivered with my 
 > defined header and footer, but the body is an attachment which can't be 
 > read. It says, "No Application Available for This Content".
 > 
 > I've looked through all of the settings and can't find anything related 
 > to it or that affects it.

The problem is almost surely that headers and footers added by Mailman
using MIME conventions are more or less incompatible with HTML mail.
Competent MUAs deal with this fine[1], but unfortunately competent
MUAs are mostly found on Unix systems, not on the popular OSes or
handheld devices.

There are workarounds for this that rewrite the HTML instead of using
MIME, but we are unwilling to support them because rewriting HTML
reliably across all of the variations put out by different MUAs
requires a huge amount of effort, and won't be successful in the end
because new variations arise daily -- it's whack-a-mole with no prizes.

There are three workarounds that usually help (you only need one).
Which is best depends on your users' preferences and list practices.
(1) Don't allow HTML mail.
(2) Have Mailman convert it to text.
(3) Don't add headers or footer at all.  This means you have to delete
    everything, including whitespace, from those text boxes in the
    admin interface.

Footnotes: 
[1]  The algorithm is easy to describe and shouldn't be hard to
implement: print the plain text header using default formatting in a
frame, print the mail itself in another frame, and then the footer in
a third frame, stacking the frames vertically.  This might be a
strategy that would work in general, but last I checked you couldn't
count on MUAs to support frames, so....