[Mailman-Users] Reply-to options not working

Stephen J. Turnbull turnbull.stephen.fw at u.tsukuba.ac.jp
Wed Jan 24 03:50:56 EST 2018

I'd appreciate if those who have strong opinions on this would take a
look at the analysis below and tell me if I'm missing something.  If
not, maybe I'll write up a BCP (non-standards-track RFC[1]) so it's on

This proposal actually has a history going back to about 2005.  I
didn't do anything about it because I got a lot of pushback from MUA
writers, and writing RFCs is worse than writing PEPs (Pythonistas are
either sane or go away soon, not so for IETF mailing lists ;-).  But
if its still an issue maybe it's worth the effort.

Grant Taylor via Mailman-Users writes:

 > What I find interesting is that mail.override_list_reply_to is set to 
 > True by default in my copy of Thunderbird, 52.5.0.

I think there's an obvious algorithm for "smart single reply":

1.  If there is a Reply-To, address the message to Reply-To.
2.  Else if there is a List-Post, address the message to List-Post.
3.  Else address the message to From.  (If there's no From, the
    message violates the most basic RFCs so all bets are off.)

Assuming that no lists munge Reply-To, I think you'll agree that this
is what you want 90% of the time (conservative estimate).  There are
some issues with this algorithm in practice:

1.  Some lists should not encourage reply-to-list (eg, for privacy
    reasons).  This can be worked around by omitting List-Post, or
    solved by additional protocol so that the list sets a header field
    saying "don't automatically reply here just because there's a
    List-Post.  Given how conservative MUA writers are, I'd say "KISS"
    for these, and make users cut-n-paste.  Most of the time a
    reply-to-list here is probably thread hijacking anyway.
2.  Some users will want to override the algorithm and reply
    specifically to list or author.  MUAs should provide buttons or
    menu items for these infrequently used options.
3.  Your favorite list munges Reply-To.  Nothing changes here, people
    are still going to be embarrassed by sending remarks intended to
    be private to a broad audience, and in some configurations of
    Mailman the original Reply-To or the From will get dupes.  At
    least you can override with a reply-to-author function.

I don't understand what Thunderbird thought they were doing. <shrug/>


[1]  MUA UI best practices like this technically don't have anything
to do with Internet protocol semantics.

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