[Mailman-Users] Question about pipermail archive threading.

Mark Sapiro mark at msapiro.net
Sun Feb 21 03:26:07 CET 2010

Mailman's pipermail archives are threaded based on In-Reply-To: and
maybe References: headers. It turns out the code always had a fallback
to thread by Subject: if there were no In-Reply-To: or References:
headers, but this fallback never worked due to a bug.

I have recently committed a fix to the 2.1 branch for the bug, so
starting with the next release, fallback to threading by subject
should work.

I have a question however. The current (fixed) code does the following:

if the current message has In-Reply-To:
    thread it to the In-Reply-To message if that message exists in
    the current volume
else if the current message has References:
    thread it to to the most recent existing message in the current
    volume in References
    thread the current message to the oldest message in the current
    volume with matching Subject.

The subject threading to "oldest" won't always be correct, but the only
reasonable alternative is "newest" and that won't always be correct
either, and I think either alternative is better than none. That's not
my question.

My question is the above logic implies that if the current message has
an In-Reply-To and the replied to message is not in the archive, the
message won't be threaded even if it has a References: to a message in
the archive.

This occurs often. A posts; B replies off list to A; A replies to B and
Cc's the list. Should A's reply to B be threaded with A's original
post? I think it should, and it can be by References or even Subject,
but I wonder if I'm overlooking some other cases in which it shouldn't
be done.

Mark Sapiro <mark at msapiro.net>        The highway is for gamblers,
San Francisco Bay Area, California    better use your sense - B. Dylan

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