[buug] Re: Reply-To:

[Michael Paoli]

Reply-To: header essentially designates a preferred e-mail address to
reply to, i.e. it typically overrides From:, effectively designating a
preferred e-mail address the originator wants the e-mail to go to.  In
typical usage with a mailing list, it generally has nothing to do with
whether or not the originator wants replies to go to the list,
themselves (via From: or Reply-To: address), or both (the only real
exception being if they set the Reply-To: to the address for the list
itself, in which case they would want replies sent to the list, rather
than themselves - this, however, would tend to violate the Principle of
Least Surprise and wouldn't be a recommended best practice, as a
replying recipient, selecting "reply" rather than "reply-all", would
have their response in such a case go to the Reply-To: and end up going
to the list - when such a replying recipient probably intended such to
go to the originator of the item to which they were replying, rather
than the list).

In typical usage, replying recipient selects "reply", and such would
most "normally" or expectedly get sent to the originator of the item
they are replying to (typically via Reply-To: or From: header in the
original message, in that order of preference), or alternatively, if   
recipient selects "reply all", such typical goes to multiple applicable
fields from the original message (e.g. Reply-To: or From: and also To: 
and Cc:).

I often quite explicitly and intentionally use Reply-To: header.  Typical
examples:

I'm sending from cheap or free or I'll probably
get-rid-of-it-some-day-and-maybe-soon ISP or free web based e-mail, and
I prefer to receive my e-mail at/via another address (such as a
long-term or permanent forwarder - perhaps one I can't originate e-mail
messages from with such a From: address - or can't easily do so (such as
they offer forwarding services, but no sending services - and maybe I
don't feel like munging or "forging" headers that much (or server(s) or
firewalls or such on the way might also reject or drop such))).

Someone sends me personal e-mail to my work e-mail address, and rather
than just forwarding it to my personal e-mail address (as I most/quite
typically do), I instead set the Reply-To: to my personal e-mail address
and use the work e-mail address to send them a reply (hence the work
address is in the From: - work sites may also block (firewall, etc.)
other access to personal e-mail access from work site, making it
difficult/infeasible/impossible to more directly originate personal
e-mail from work).

Same scenario as above, except swap the work and personal around the
other way.

(rare) I might send on someone's behalf or for them and want replies
directed to them (I'd typically also Cc: them when sending such an
e-mail).  Note also that per the RFC(s) there's theoretically another
way of dealing with such a scenario, but it's rarely used in practice  
(e.g. if I was administrative professional of the person and they
dictated the memo to me, I could set them as From: and myself as Sender:
but most mail client software doesn't conveniently lend itself to such 
use, and much client software wouldn't easily let recipient be able to
see and/or distinguish and/or distinctly and separately choose when
replying, between From: and Sender: addresses.  In practice, Sender is
used for much more autonomous (or semi-autonomous) Senders, e.g. mail list
software).

Note that with typical BUUG usage, what does or doesn't get the reply to
go to the list has nothing to do with the presence (or lack thereof) of
a Reply-To: header.  It's the To: header which is generally
buug at weak.org, and hence a "reply all" action by recipient(s) includes
sending to buug at weak.org.

references/excerpts:

> From: nick at zork.net (Nick Moffitt)
> Date: Thu, 13 Nov 2003 19:40:10 -0800
> Subject: [buug] connecting between linux machines?
> In-Reply-To: <20031114012709.GX11857 at linuxmafia.com>
> References: <3FB42CDF.3000503 at ncseweb.org>
<20031114012709.GX11857 at linuxmafia.com>
> Message-ID: <20031114034010.GF24670 at zork.net>

> begin  Rick Moen Lives Three Hours from Nowhere  quotation:
> > Quoting Skip Evans (skip at ncseweb.org):
> > > Reply-To: skip at ncseweb.org
> >
> > I'm overriding your Reply-To header, because this mailing list isn't
> > really a private consulting service, and the idea is supposed to be
> > for listmembers (and people finding the Web archives) to benefit
> > from the questions and answers.

>         And that's why individual reply is separate from group reply.
> The whole point of the no-munging argument is so that skip can do
> precisely what he did without interfering with the path of list
> replies (or being interfered with thereby).

Quoted from RFC #  822:
"
     4.4.3.  REPLY-TO / RESENT-REPLY-TO

        This field provides a general  mechanism  for  indicating  any
        mailbox(es)  to which responses are to be sent.  Three typical
        uses for this feature can  be  distinguished.   In  the  first
        case,  the  author(s) may not have regular machine-based mail-
        boxes and therefore wish(es) to indicate an alternate  machine
        address.   In  the  second case, an author may wish additional
        persons to be made aware of, or responsible for,  replies.   A
        somewhat  different  use  may be of some help to "text message
        teleconferencing" groups equipped with automatic  distribution
        services:   include the address of that service in the "Reply-
        To" field of all messages  submitted  to  the  teleconference;
        then  participants  can  "reply"  to conference submissions to
        guarantee the correct distribution of any submission of  their
        own.

        Note:  The "Return-Path" field is added by the mail  transport
               service,  at the time of final deliver.  It is intended
               to identify a path back to the orginator  of  the  mes-
               sage.   The  "Reply-To"  field  is added by the message
               originator and is intended to direct replies.

     4.4.4.  AUTOMATIC USE OF FROM / SENDER / REPLY-TO

        For systems which automatically  generate  address  lists  for
        replies to messages, the following recommendations are made:

            o   The "Sender" field mailbox should be sent  notices  of
                any  problems in transport or delivery of the original
                messages.  If there is no  "Sender"  field,  then  the
                "From" field mailbox should be used.

            o   The  "Sender"  field  mailbox  should  NEVER  be  used
                automatically, in a recipient's reply message.

            o   If the "Reply-To" field exists, then the reply  should
                go to the addresses indicated in that field and not to
                the address(es) indicated in the "From" field.
"

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