Gateway to python-list is generating bounce messages.

Ben Finney bignose+hates-spam at
Wed Sep 17 10:34:00 CEST 2008

Maric Michaud <maric at> writes:

> Le Monday 15 September 2008 16:45:12 Maric Michaud, vous avez écrit :
> > This is not sufficient for auto-responses, and given the following
> > rfcs, it would smart to both :
> >
> ...
> > - add or modify the Return-Path and/or Reply-To header for badly
> > implemented auto-responders to point to list maintainer.
> Oh, no ! to the list itself of course.

Those fields have a defined use, and neither is suitable for munging
by mailing list software

The mandatory 'Return-Path' field records the address given in the
MAIL FROM command that transported the message. This is defined in RFC

The optional 'Reply-To' field, if used at all, records the address
that the author of the message suggests for return correspondence.
This is defined in RFC 2822.

Neither of these fields is suitable for tampering by mailing list
software; 'Return-Path' is set when the message is first sent, and
'Reply-To' is for use by the *author* of the message, not by software
that later handles it.

Mailing list programs record their information in several fields all
of which start with 'List-' and defined in RFC 2369. The purpose you
seem to be describing, the list posting address, is recorded in the
'List-Post' field, which records the URL to use for sending
contributions to the same maling list.

A summary of all header fields for use in mail and MIME is at RFC

> This could also avoid the common mistake mailing list users do in
> replying private mail accidentally when the adress of the list is
> only present in CC field.

That mistake is easy to correct, without breaking standard definitions
of fields: the user can simply send the message again to the correct
destination. (I would suggest that, to help avoid repetition of this
mistake, the user then pressure their software vendor to incorporate
the "Reply to list" function making use of the standard 'List-Post'
field in every list message.)

Munging other fields such as 'Reply-To' leads to other common mistakes
that are far more damaging: replies that were intended only for the
author are sent to the 'Reply-To' address (as defined by the
standard), but instead get sent to the entire list. This damage is
usually impossible for the user to undo.

If the software you use still isn't following the internet mail
standards, then fix the software, or pressure your vendor to do so.

 \           “Are you pondering what I'm pondering?” “Umm, I think so, |
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_o__)                                                   and The Brain_ |
Ben Finney

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