Okay, I dug out the "reply problem list" I had written as part of the
DRUMS discussions, and edited it slightly.
I've tried to define these problems in terms of observed behavior, not
in terms of "we need a header that does X". This was an attempt to avoid
prejudicing readers to favor some anticipated solution. Also in these
discussions there seems to be a tendency to define problems in terms of
assumed solutions, which makes it difficult to compare one proposed
solution with another one. ("the problem is that we don't have a FOO
header; so if we had a FOO header the problem would be solved").
Many of these problems are very similar to one another, especially if
you group them in terms of "this problem is solved by adding header
FOO". I have listed them as separate problems because some proposed
solutions will solve one problem while failing to solve a similar one.
By listing so many separate problems, I don't mean to imply that they're
all of equal severity.
I separated the original list into two sections. List A consists of the
problems that aren't related to lists munging Reply-To. List B consists
of the problem related to lists munging Reply-To. I'm guessing that
hardly anyone on this mailing list still believes its good practice for
lists to mung Reply-To, so for the time being I'm posting just List A
here. If you want to see both lists, look at
http://www.cs.utk.edu/~moore/opinions/reply-problem-list.html .
My reason for compiling this is to help clarify arguments of the form
"proposal X doesn't solve problem Y". It appears that any solution to
the _set_ of problems is likely to involve several changes: perhaps a
new header field or two, along with (perhaps) recommendations to MUA
authors about their user interfaces, modifications to various kinds of
software, and maybe some user education. With this list we can compare
various _sets_ of solutions to this _set_ of problems.
List A: REPLY problems not involving modification of message headers by
mailing lists:
A1. Given the vast number of MUAs that implement a "reply all" command
where the Reply-To address only replaces the From address from the
original message, there's no good way for the author of a message to say
"please reply only to these addresses", or (almost equivalently) "please
don't reply to these addresses". The author can use Bcc for all
recipients who should not receive the reply, but that doesn't inform the
"non blind" recipients that the other recipients were also sent copies
of the message.
A2. If a message contains a Reply-To field, but the person composing the
reply isn't aware that Reply-To is being used, the reply may go to
somewhere besides where the reply author thought it should go. The
result may be surprising or embarrassing (as when a personal reply gets
sent to a list), or the reply author may think he has sent the message
to a list when it has really only gone to one particular recipient.
A3. A few MUAs implement only one kind of reply -- which uses Reply-To
if present and From otherwise. Users of such MUAs have difficulty
participating in group discussions on mailing lists (unless the list
mungs Reply-To).
A4. If a message is sent to a mailing list, and someone does a "reply
all" to that message, the author often gets two copies - one sent to the
From address and another sent to the list address (which presumably
appeared in the To or Cc field of the subject message).
A5. If a user is subscribed to multiple mailing lists, and a message is
sent to more than one of those mailing lists, the user will get multiple
copies of the message. This might not be so bad, but the same user will
also get duplicate copies of the message every time someone does "reply
to all" to the original messages or any of the replies to that message.
A6. On many MUAs, if the sender specified Reply-To, the recipient is
stuck with that - he cannot easily edit it to reply to From or
From+To+CC (especially if he cannot see the original headers while he's
editing the reply recipient list). The author of the reply thus
sometimes has difficulty sending the reply to where it needs to go.
A7. If someone responds to a list message and CCs themselves in the
response, everyone who does a "reply all" to that message will also Cc
that person...even if he's on one of the lists. Alternatively, if
multiple recipients (often lists) get CCed on a message, every "reply
all" goes to all of those recipients, even if the discussion topic
wanders and it's no longer appropriate for many of those recipients.
A8. Many people have multiple mailboxes, or regularly send mail from
some account at which they don't want to receive mail. If they use
Reply-To to point to their preferred mailbox, it will prevent some
recipients from doing "reply to all". Also, since there's no indication
as to why the author used Reply-To (it could be "please don't mail to me
at my From address" or it could be "please tell my secretary, not me,
whether you'll be at the meeting"), it's easy for a reply to go to the
wrong place.
A9. Mailing list subscribers who don't understand the reply functions of
their UA or who have UAs with severely limited reply functions often
send replies to the author of the message when they should go to the
list. This causes discussions on the list to suffer and perhaps die out.
A10. Mailing list subscribers who don't understand the reply functions
of their UA, often send replies to the mailing list when they should go
to the author of the message. This causes prolonged discussions on a
list on which such discussions are inappropriate.