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+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. + +
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. + +
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. + +
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. + +
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 message. + +
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. + +
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. + +
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. + +
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. + +
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. + +
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: + +
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. + +
+
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$Id: reply-to-harmful.html,v 1.20 2002/11/15 03:46:04 chip Exp $+ + + diff --git a/papers/reply-to/useful.html b/papers/reply-to/useful.html new file mode 100644 index 0000000..56faa92 --- /dev/null +++ b/papers/reply-to/useful.html @@ -0,0 +1,272 @@ + + + +
This page has been mirrored for historical preservation
+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. Many list administrators want to add a +Reply-To header that points back to the list. This transformation +is also one of the most useful. + +
Some administrators claim that Reply-To munging +can have harmful -- even dangerous -- effects. I assert the opposite, +that not adding a Reply-To header has even more +harmful effects. If you think +Reply-To munging is a bad idea, I hope I can change your +mind. + +
The first thing to consider is that +RFC 822, the document which +defines the standards and usages for email, specifically mentions this usage in +section 4.4.3: + +
+ 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. ++ +
Aside from this official sanction, there are a number of reasons for munging +the Reply-To header. The arguments which follow are my own. +They may not be comprehensive, but I think they are compelling. + +
The ``Principle of Minimal Bandwidth'' is a good rule that will keep +you out of trouble. It says that you should make any changes +which will reduce the amount of email traffic on the Internet. +The ``Principle of Minimal Bandwidth'' 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. + +
This is frequently quite annoying to the original sender, who now +receives two copies of the reply. Furthermore, in many cases the original +sender has added additional recipients. Not only does "reply to all +recipients" send the reply to each of these additional recipients +(who are frequently also members of the list), it also propagates this +list of recipients onto the reply to the list. + +
The effects of this snowball, as each additional person replies to the +messages using "reply to all recipients", they become the sender, and thus +get added to the list of recipients with the next reply. Thus the list of +recipients grows and grows. Frequently, as the subject matter changes, +members of the list find themselves receiving multiple copies of messages +which have strayed from the topic in which they were originally interested, +even after they have unsubscribed from the list. + +
Many people have pointed out that it is relatively easy to implement a +procmail filter to remove duplicates. This attitude merely reveals +a Unix-centric and US-centric viewpoint. Many users of inferior operating +systems do not have a tool powerful enough to ensure the removal of +duplicate messages. Furthermore, in many European countries, connect time is +charged by the minute. Even with procmail, the duplicates +have to be downloaded before they can be filtered, resulting in +unnecessary additional expenses for some of our European list mates. + +
This last fact reveals that the issue is really related to bandwidth. +By applying the ``Principle of Minimal Bandwidth'', we conclude that it +is necessary to add a Reply-To header that points back to the list. + +
If you use a reasonable mailer, Reply-To munging does +provide new functionality, namely the ability to reply only to the +list. Furthermore, it does not decrease functionality. In Pine, +for example, when there is a Reply-To header, Pine will ask, +``Use "Reply-To:" address instead of "From:" address?'', easily allowing +one to reply only to the original author. In KMail, it is even easier. One +merely right-clicks on the hyperlinked From address. + +
If your mailer doesn't have this option, you should request it from its +development team. Any mailer, whose development team refuses this simple +request due to some ideological position, cannot be said to be reasonable. + +
Since
There are, unfortunately, some poorly implemented mail programs that lack +separate "reply-to-author" and "reply-to-group" functions. A user saddled +with such a mailer can benefit from Reply-To munging. It makes +it easier for him or her to send responses directly to the list. + +
Furthermore, this change does not penalize the conscientious +person that uses a reasonable mailer. Reasonable mailers give one the +ability to reply to the From address. Therefore, it would be +unkind to further penalize those with poorly implemented mail programs, since +munging the Reply-To header causes no harm to those with reasonable +mailers. + +
For discussion type lists, I would estimate that ninety percent of the time, +people want to reply to the list. Without munging, they either have to break +the ``Principle of Least Bandwidth'', or type in the list address. Many people, +being lazy, will choose the former, sending unnecessary copies of emails to +people who will either have to delete them, or take the time to set up a +filter (if they are lucky enough to be running an operating system which +facilitates this). + +
On the other hand, about ten percent of the time, replying to the sender +might be more appropriate. Even if the respondant has an unreasonable +mailer (a decision for which they are probably responsible), the worst case +scenario is that they have to type in an address ten percent of the time. +Of course, if they took the time to add this recipient to their address book, +they could reduce the amount of typing to a minimum. + +
So, which produces least total work: typing in the list address ninety +percent of the time (plus possibly taking the time to set up a filter), or +typing in an individual's address ten percent of the time? + +
I'll take munged Reply-To headers every time, thanks. + +
Some administrators claim that munging Reply-To headers is +harmful because it surprises people, and can cause damage when things go +awry. They assert that administrators should prevent the possibility of a +private message being mistakenly broadcast to the entire list. + +
This is simply not the responsibility of the administrator. People are +responsible for their own mistakes. If someone is sending a private email +which is derogatory, or otherwise embarrassing were it to be made public, +they should probably be sending it directly, rather than as a reply to a +public message. They should also pause and think about whether they should +be sending it at all. This pause should be quite sufficient for a +conscientious person using a reasonable mailer to catch any mistake that +they might be about to make. + +
In any case, it is an entirely trivial matter for the list administrator +to provide an obvious clue in the subject line of every message that the +message was received from a mailing list. If your Mailing List Manager doesn't +provide an option to prepend "[listname]" to the subject, then switch to one +that does ( e.g. GNU MailMan +or Majordomo ). + +
If you are not convinced yet, then allow me one final plea. Most mailing +lists are intended to facilitate discussion on a given topic. If this is +indeed the primary purpose of your list, then you really should add a +Reply-To header which directs replies to the list. This helps to +ensure that the entire thread of the conversation is available to all who +might be interested. + +
I can't count the number of times I have searched the archives +of a list for a solution to a problem, only to find the question asked, but +no solution. Yet, when I subsequently post the question to the list, the +long-time members insist that it has already been discussed, and that I should +search the archives. If I'm lucky, a newer member forwards to me the private +reply which answered the question. + +
Thus, munging the Reply-To header benefits those lists which are +intended for serious discussion. If your list is intended primarily for +announcements or other one-way mailings, you may safely ignore these arguments. + +
I have been and am subscribed to both munging and non-munging mailing lists. +On the non-munging lists, there are regular requests to change the list so +that Reply-To replies to the list. On the munging lists which +already do this, there are hardly any requests for change. + +
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 both of these things, and is a very good idea. To reiterate: + +
+
There are, of course, a few details that need to be addressed to make +Reply-To munging more pleasant and productive for everyone. One +potentially serious problem with Reply-To munging is the possibility +of mail loops. It should be possible for the list server to detect and prevent +this. If anyone has any patches to implement this feature, I would be happy +to provide a link to the patch on your ftp server, or to make it available on +my own ftp server. + +
Also, patches are needed for any mailers that do not implement the ability +to reply to the From address. Please send links or patches to me +at sdhill at metasystema.net. Thanks. + +
+A patch for Emacs rmail is available at: http://www.metasystema.net/pub/patches/emacs/rmail-query-reply-to.el. + +
I originally wrote this essay as a response to Chip Rosenthal's + +Reply-To Munging Considered Harmful. + +
+
Simon Hill +sdhill at metasystema.net + + +