OT: broken mail threads

Lauri Alanko la@iki.fi
Tue, 20 Aug 2002 10:12:03 +0300

I'm sorry to bring up such petty issues, but this has been nagging me
for quite a long while now... 

The Haskell mailing lists have one rather unflattering characteristic:
their mail threads are almost always broken.

I'll elaborate. Most mail user agents arrange messages in threads,
keeping track of which message is a reply to which. The programs use the
In-Reply-To: and References: -headers of the messages for this.

By some coincidence, the various Haskell mailing lists have an
uncommonly high proportion of replies which do not have these headers.
As a result, many followup messages show up as a new thread in the
unlucky reader's mail program, and this makes following a discussion
more inconvenient. This also affects web archives of the mailing lists.

The reason for these lacking headers is most likely faulty mail
programs. Since programs are at fault here, not people, I won't mention
names, but will simply identify the most common broken user agents.

X-Mailer: Claris Emailer 2.0v3, January 22, 1998
(No threading information of any kind)

X-Mimeole: Produced By Microsoft Exchange V6.0.6249.0
(Does have some very non-standard Thread-Topic: and Thread-Index:
-headers, but no In-Reply-To: or References:)

User-Agent: slrn/ (Linux)
(Apparently via a mail-news -gateway. Replies do have a References:
-header, but with locally generated message-ids instead of the real

There are also other messages with threading problems, but these are by
far the most common sources.

If you find yourself using one of these programs, could you please check
your configuration or maybe consider switching to a more well-behaving
user agent? This would make your messages much easier to follow.


Lauri Alanko