Reply-To munging summary (was: Bug in mailing lists; unfriendly to non-subscribers)

Felipe Contreras felipe.contreras at
Thu Jul 8 10:29:17 UTC 2010


I haven't seen a summary of this big thread, so I'm going to try to
write one. I'll focus on Reply-To munging here (orthogonal to

Before starting it's worth to keep in mind that munging is a *default*
that is possible to manually change, and some clients have the option
to ignore it. However, the people who do that are the _minority_; most
people just hit reply, and many use typical clients. In order to fully
understand the benefits of one method over the other, we shall only
consider the behavior of the mailing list as a whole, not what some
particular individual might or might not do.

For example, when analyzing personal level indicators, an advantage of
not munging; it's not useful to concentrate on the fact that *some*
people might ignore the Reply-To header, and therefore the indicator
would appear for that particular mail. The fact remains that for most
of the posts in the mailing list, the feature will not work. IOW: what
is important is whether or not the user can rely on the feature.

== Advantages ==

1) Personal level indicators.

Gmail has a feature that places a neat marker (">") near the subject
of the mail so that you can see directly that the mail was addressed
to you. This is specially a nice feature in high traffic mailing
lists. Here's a screenshot:

mutt can be configured to have similar highlights:
color index brightwhite black "~p" # to me

2) Recipient filtering

It's possible to search say 'to:linux-kernel at to:me';
with munging it's not possible because the To header is automatically
changed to the mailing list.

Similarly, it's possible to have a filter rule for all mail from
linux-kernel to move to a certain folder, but have an exception for
mail addressed to the user, which might go directly to the inbox.

This way, both with personal level indicators and recipient filtering,
it's much easier to quickly be alerted of incoming mail addressed to

3) Consistency

When there's Reply-To munging, people might choose to ignore it (if
their client supports) that. So in a typical munged mailing list you
have both munged and non-munged posts.

This is not a strong argument, but it's useful to keep in mind while
reading the non-issues below.

There are other advantages, not not relevant in the current Fedora context.

== Disadvantages ==

1) Inadvertently forgetting to "reply to all"

When Reply-To munging is not used, the user is presented (in typical
clients) with the option to either "reply" or "reply to all".
Sometimes the user will select the wrong one, which is an annoyance.

The severity of this problem is impossible to calculate as it depends
on background of the members of each mailing list, which might be very
varied, and in flux.

=== Non issues ===

Many arguments were presented as disadvantages of munging which are
not valid IMO and I presented reasons for that (as I'm doing here).

1) Ignorance of "reply to all"

While there might be some rare cases where the user doesn't know about
"reply to all" (i.e. mail newbies, grandmas, etc.), the typical mail
user is well aware of "reply to all" as it's the only way to keep a
conversation between more than two persons. It's probably one of the
first things to learn.

Personally I have never seen cases of this, and nobody has provided
evidence. If there's any cases of this, they are probably very

2) Two copies of the same mail

When a mail is not munged, the original author would be in the To
field, and the list on Cc. If the author is subscribed on the mailing
list (the only case we care about here), then the author would receive
a direct copy and another copy from the list.

However, this is not the case as mailing list servers are aware of
these cases and don't send the list copy. For example, mailman has an
option "Avoid duplicate copies of messages" which does precisely that,
and is enabled by default.

This was agreed to not be an issue.

3) Unwanted direct addressing

There was an argument that some people didn't want to be directly
addressed and wanted mails addressed to the mailing list only.

There was no mention of why people would want that, or any evidence of
such cases (if there's any).

Moreover, Reply-To munging doesn't prevent them from being directly
Cc'ed (that header filed is not munged), they can manually be added to
the To field, or somebody might ignore the Reply-To header.

At best this is a policy issue, not related to Reply-To munging.

4) FWD noise

If the user mistakenly misses the "reply to all" option, the mail is
sent privately, then the user might notice and choose to fwd the mail
back to the mailing list.

This is a double mistake by the user, the proper way to correct the
original mistake is to send the mail again properly, and as to discard
the private copy.

Just like top-posting; this is solved with policy.

5) Mail escaping

This is defined as mail that is sent privately by mistake and is never
noticed, hence escaping the mailing list.

No evidence was provided of this considerably affecting any mailing
list, so at best the damages are marginal.

== Personal opinion ==

My feeling is that Reply-To munging is being widely used because it's
being widely used; IOW: inertia. It seems like a good idea at first,
until you realize the loss of functionality. Most people don't realize
the features they are missing, and instead only concentrate on the
convenience of not having to choose between two options.

== Conclusion ==

Once you weed out all the invalid arguments, the analysis is very simple:

 1) Not munging allows some nice features
 2) The only thing munging does is prevent inadvertent private replies

So it's a matter of putting in a balance what is more desirable: the
features, or preventing the mistakes. IMO the result is obvious, since
the people that would benefit from the features would do it in a very
big way, and the amount of people that would be affected by mistakes
is not known.

Also, people that are used to Reply-To munging can get used to
clicking "reply to all"; it's a matter of habit, but no functionality
is lost. OTOH the people that enjoy the benefits of not munging can't
really do anything to make the features work; it's not possible,
period. So IMO munging advocates are being egotistic by not giving
away a tiny bit of their convenience in order to enable features other
people love and rely on for efficient mail handling.


Felipe Contreras

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