I have some very strong opinions about the proper way to run mailing lists, particularly in the context of free software development.

Discussion lists should not set the Reply-To header

The Reply-To issue is that many people would like to make it very easy to reply to messages on a mailing list for discussion so that the replies go to the list instead of the person who wrote the message they are replying to. For example, if Alice sends a mail to the list, and Bob wants to reply, he wants the mail to the list, to continue the discussion in public, rather than just to Alice.

The Reply-To header sounds like the perfect way to do that. It is, after all, the header to say where replies should go. Unfortunately, using it leads to problems. It makes mailing list mails behave different from other mails, and it makes it easier to send the reply to the list by mistake, and that will lead to messages that were meant to be private to be public instead.

There are three different kinds of replying:

  1. Reply to sender only.
  2. Reply to sender, and every else the mail was addressed to (in the To and Cc headers). This is often called "group reply".
  3. Reply to list only.

All relevant e-mail software supports both 1 and 2, and everyone is used to choosing between them. If Reply-To is set to point at the list, then 1 and 2 stop being distinct. This will increase the number of mails sent to the list by mistake.

Some e-mail software does not support 3. Most of the free software ones do, because their developers are on many mailing lists and they need it. Proprietary e-mail software seems to often be written by people who do not actually use e-mail and do not read the relevant IETF specifications.

Let me rephrase that more clearly: you do not need Reply-To to have an easy way to reply to the list. You need to use "reply to list" in your e-mail software instead.

In Mutt, it is capital L. In Evolution it is control-L.

Adding list name to Subject header

Having the name of the mailing list at the beginning of the Subject header makes it easier to see, at a glance, which mails in your inbox come from which mailing list. So that's obviously a good thing.

Except it doesn't do that.

Suppose Alice sends a mail to the list, and the list adds the name to the subject line. Bob then sees a mail with the subject [atheists-are-sexy] I made some Darwin fishes. Bob then responds privately, since he wants to buy one of the fishes, but does not adjust the subject line. Alice will then see the same subject line. Adding the list name to the subject does not, in fact, tell Alice whether Bob's e-mail came in via the list or just directly to her.

Adding the list name to the subject line does, however, guarantee that there is less space for useful information.

Every mailing list worth anything instead adds the List-Id header:

List-Id: <debian-devel.lists.debian.org>

You can use this in several ways:

  • You can automatically put mailing list mails into their own folder, using server side filtering, such as Sieve or procmail.
  • You can use client-side filtering to do the same thing.
  • You can use client-side virtual folders to have a search-based folder for list mails, but still keep them in your inbox.
  • You can color list mails with a different color from personal mails.

If you're using e-mail a lot, and participating in mailing lists, learning to set up such custom filters is well worth your time.

Meta discussions

If you have a suggestion for a way to improve the way the list operates, do not send the suggestion to the list. Meta-discussions are distracting, and can be disruptive. Send any such suggestions to the list owner or administrator instead.

If there's a need for a lot of meta discussion, request setting up a separate list for that.