RE: [NTISP] PostOffice List question

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Matthew Thompson (
Thu, 14 Dec 2000 13:33:30 -0000

Message-ID: <900E7814F4BCD111B5F600600877FCD1014A8DD4@MAIL_SERVER>
From: Matthew Thompson <>
Subject: RE: [NTISP] PostOffice List question
Date: Thu, 14 Dec 2000 13:33:30 -0000

Please re-consider doing this - it has the potential to do more harm than
good - and without meaning to insult anyone, how can you be sure of the
effect it will have on the many mis-configured mail servers and systems out
in the real world where people are not so clued up as to subscribe to
mailing lists to ask for assistance.

``Reply-To'' Munging Considered Harmful
An Earnest Plea to Mailing List Administrators


An email message requires some amount of processing when it is redistributed
to a mailing list. At the very least, the envelope must be rewritten to
redirect bounces directly to the list administrator. While the message is
being processed, the list administrator might take advantage of the
opportunity to munge some of the message headers.

Some forms of header munging are helpful, such as special loop-detection
headers. Others are questionable. Most are ill-advised or dangerous. Many
list adminstrators want to add a Reply-To header that points back to the
list. This transformation also is one of the most ill-advised.

Some administrators claim that Reply-To munging makes it easier for users to
respond to the entire list, and helps encourage list traffic. These benefits
are fallacious. Moreover, Reply-To can have harmful -- even dangerous --
effects. If you think Reply-To munging is a good idea, I hope I can change
your mind.

The Principle of Minimal Munging
Email processing is pretty tricky. Read through RFC-822, the Standard for
the Format of ARPA Internet Text Messages, sometime. It is 47 pages of
dense, dry detail. A lot of engineering and consideration went into this
work. Even still, RFC-822 leaves many corner conditions and specialized
circumstances poorly specified. RFC-1123, the commonly-called Internet Host
Requirements document, adds a couple dozen more pages, and remedies some of
the defects. Then there is MIME, X.400 mapping, and a handful of other
standards and conventions -- some documented and some folklore. Email
handling is surprisingly complicated, and even an innocuous-sounding change
might have grave, unintended consequences.

The ``Principle of Minimal Munging'' is a good rule that will keep you out
of trouble. It says you should not make any changes to an email header
unless you know precisely what you want to do, why you want to do it, and
what it will affect. Unless you can articulate a clear reason for munging
and understand the full consequences of the action, you should not do it.

The ``Principle of Minimal Munging'' will help you avoid the sorts of
problems we are about to discuss. This principle is a rule designed to be
broken, but you can avoid some significant heartache by thinking hard and
long before you do so.

It Adds Nothing
Reply-To munging does not benefit the user with a reasonable mailer. People
want to munge Reply-To headers to make ``reply back to the list'' easy. But
it already is easy. Reasonable mail programs have two separate ``reply''
commands: one that replies directly to the author of a message, and another
that replies to the author plus all of the list recipients. Even the lowly
Berkeley Mail command has had this for about a decade.

Any reasonable, modern mailer provides this feature. I prefer the Elm
mailer. It has separate ``r)eply'' and ``g)roup-reply'' commands. If I want
to reply to the author of a message, I strike the ``r'' key. If I want to
send a reply to the entire list, I hit ``g'' instead. Piece 'o cake.

I mention Elm here (and a lot later on) simply because that's the mailer I
use everyday. This sort of support is not unique to Elm Any reasonable
mailer provides it. The Pine mailer, for instance, asks directly, ``Reply to
all recipients?'' when you use the ``r'' command. It doesn't get much easier
than that!

Whichever mailer you choose, please read the fine manual that comes with it.
Unless you are stuck with some decrepit mail system, I bet you'll find it
has a similar feature. If so, you easily can choose to direct your responses
either to the original author or the entire list. Mauling the mail headers
doesn't make it any easier.

It Makes Things Break
If you use a reasonable mailer, Reply-To munging does not provide any new
functionality. It, in fact, decreases functionality. Reply-To munging
destroys the ``reply-to-author'' capability. Munging makes this command act
effectively the same as the ``reply-to-group'' function. We haven't added
anything new, we've only taken away. Reply-To munging is not merely benign,
it is harmful. It renders a useful mail capability inoperative.

Freedom of Choice
Some administrators justify Reply-To munging by saying, ``All responses
should go directly to the list anyway.'' This is arrogant. You should allow
me to decide exactly how I wish to respond to a message. If I feel a public
response is justified, I'll hit the ``g'' key and tell Elm to do a
group-reply. If I believe a private response is more appropriate, I'll use
``r'' to send one. Please allow me the freedom to decide how to handle a

Can't Find My Way Back Home
It may be impossible to reply to the author of a message once the Reply-To
header is munged. The Reply-To header was not invented on a whim. It is
there for the sender of a mail message to use. If you stomp on this header,
you can lose important information.

There are good reasons why the sender might insert a Reply-To header. The
sender might not be the original author of the message (the name that
appears in the From header). If responses should return to the sender and
not the original author, then the sender will insert a Reply-To header. Or,
maybe the sender added a Reply-To because he or she cannot receive email at
the account from which the message was sent. There are many good reasons to
place a Reply-To header into a mailing list message.

If the Reply-To is munged by the mailing list, the value provided by the
original sender is lost. Reply-To munging can make it impossible to reach
the sender of a message.

Coddling the Brain-Dead, Penalizing the Conscientious
There are, unfortunately, poorly implemented mail programs that lack
separate reply-to-author and reply-to-group functions. A user saddled with
such a brain-dead mailer can benefit from Reply-To munging. It makes it
easier for him or her to send responses directly to the list.

This change, however, penalizes the conscientious person that uses a
reasonable mailer. This is a poor trade-off. As Internet list
administrators, we should encourage people to run reasonable software. If a
few people need to type in a full reply address so that everybody else can
use all the features of their mailer, I say, ``Fine!'' We should not
penalize the conscientious to coddle those who run brain-dead software.

Principle of Least Work
Compare and contrast: the work required for me (or any other Elm user) to
reply on lists that do and don't employ Reply-To munging.

                Case One: Case Two:
Action Without Munging With Munging
============= ===================== =====================

Reply to Hit the "g" Probably hit the "r"
everybody. key. key, but maybe the "g"
                                        key if there were other
                                        recipients of the message.

Reply just Hit the "r" Look at the original
to author. key. message header, write
                                        down the sender's
                                        email address, hit the
                                        "r" key, call up the
                                        header editing menu,
                                        erase the current To:
                                        value, and type in the
                                        sender's full email
                                        address. And pray the
                                        correct address wasn't
                                        wiped out when the Reply-To
                                        was munged.

Again, your preferred mailer probably implements this feature in a different
fashion. Nonetheless, it should be easy. I'll take box number one, Monte.

Principle of Least Surprise
When I hit the ``r'' key in Elm, it sends a response to the author of a
message. When you munge the Reply-To header you change this action so that
it does something entirely different from what I expect. This creates
specialized behavior for your mailing list, which increases the potential
for surprise. I'm not schooled in the science of human factors, but I
suspect surprise is not an element of a robust user interface.

Private messages frequently are broadcast across lists that do Reply-To
munging. That's an empirical fact. It's what happens when you violate the
principle of least surprise.

Principle of Least Damage
Consider the damage when things go awry. If you do not munge the Reply-To
header and a list subscriber accidentally sends a response via private email
instead of to the list, he or she has to follow up with a message that says,
``Ooops! I meant to send that to the list. Could you please forward a copy
for me.'' That's a hassle, and it happens from time to time.

What happens, however, when a person mistakenly broadcasts a private message
to the entire list? If the message is a complaint about the personal hygiene
of sender's boss, or the sex life of his or her roommate, a simple
``Ooops!'' won't cut it. About all you can do is send a followup with lots
of retroactive smileys (weak). Or say your cat was dancing on the keyboard
(better). Or start reading the classifieds for a new job/roommate/set of
teeth (most likely).

Reply-To munging encourages catastrophic failure modes. Sure, you don't need
Reply-To munging to create this sort of damage. A simple slip of the fingers
will suffice. When, however, you violate the ``Principle of Least Surprise''
you invite this sort of disaster. A responsible list administrator will
avoid creating avenues that lead to such extreme damage.

And in the End...
If you are not convinced yet, then allow me one final plea. I contribute to
the Elm mailer development team. I get to see a lot of the wants and
requests from the user community. Guess what feature more and more people
are asking for? A third reply command -- one that ignores any existing
Reply-To header! Want to guess why people are asking for it? If you think
you are doing your subscribers a service by munging Reply-To headers, you
are kidding yourself. You are making your subscribers miserable.

Some list administrators, even after reading all this, seem to say, ``Oh,
it's not that bad. Besides, my subscribers like it!'' If they do, it's
probably because they haven't bothered to learn to use the
``reply-to-group'' feature of their mailer. Instead of going through all the
trouble of making your list gateway scribble on email headers, how about
making an effort to educate your subscribers?

Many people want to munge Reply-To headers. They believe it makes
reply-to-list easier, and it encourages more list traffic. It really does
neither, and is a very poor idea. Reply-To munging suffers from the
following problems:

It violates the principle of minimal munging.
It provides no benefit to the user of a reasonable mailer.
It limits a subscriber's freedom to choose how he or she will direct a
It actually reduces functionality for the user of a reasonable mailer.
It removes important information, which can make it impossible to get back
to the message sender.
It penalizes the person with a reasonable mailer in order to coddle those
running brain-dead software.
It violates the principle of least work because complicates the procedure
for replying to messages.
It violates the principle of least surprise because it changes the way a
mailer works.
It violates the principle of least damage, and it encourages a failure mode
that can be extremely embarrassing -- or worse.
Your subscribers don't want you to do it. Or, at least the ones who have
bothered to read the docs for their mailer don't want you to do it.
In case you are wondering, yes, I once thought Reply-To munging was a nifty
idea. I got better though.

When I started running email lists, I munged 'em all. One day I accidentally
sent a private, personal reply out over one of my own damn lists. If the
list owner can't remember how to use the list properly, no way will the
subscribers be able to sort it out. I stopped munging the very next day.

On the whole, it has worked out quite well. Yes, on occasion somebody
mistakenly responds directly to the author of a message when they wanted to
reply to the group. Most folks, however, seem to catch on pretty fast to how
it works, and seem to appreciate the flexibility. Moreover, private
responses mistakenly sent to the entire list have become an almost
unheard-of event.

-----Original Message-----
From: Greg Lowthian []
Sent: 13 December 2000 21:20
Subject: [NTISP] PostOffice List question

Is there a way to set a mailing list on PostOffice so when you select Reply
it will reply to the list and not the sender of the last mail to the list.

Greg Lowthian
General Manager
Inforum Internet Services
Simply Internet
8963 Complex Drive Suite F
San Diego, CA 92123
858-565-7873 x111

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This archive was generated on Thu Dec 14 2000 - 05:20:44 Pacific Standard Time