From: Mark Anderson <markr.anderson@amd.com>
To: Marten Veldthuis <marten@veldthuis.com>, Carl Worth <cworth@cworth.org>,
	notmuch <notmuch@notmuchmail.org>
In-Reply-To:
 <87my1kkzbn.fsf@marten.i-did-not-set--mail-host-address--so-tickle-me>
References: <1260400470-sup-5775@testarossa>
	<87ws0ug23f.fsf@yoom.home.cworth.org>
	<87ljha3avx.fsf@home.veldthuis.com>
	<87ocm64ivu.fsf@yoom.home.cworth.org>
	<87my1kkzbn.fsf@marten.i-did-not-set--mail-host-address--so-tickle-me>
Date: Wed, 23 Dec 2009 15:07:47 -0700
Message-ID: <3wdzl59mjik.fsf@testarossa.amd.com>
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Subject: Re: [notmuch] Threading
Precedence: list

On Tue, 15 Dec 2009 16:54:20 +0100, Marten Veldthuis <marten@veldthuis.com> wrote:
> On Thu, 10 Dec 2009 13:30:13 -0800, Carl Worth <cworth@cworth.org> wrote:
> > But I still have a hard time justifying user operations to manipulate
> > threading. The whole point of threading is to make it faster to process
> > and read messages. But manual operations like joining and splitting
> > threads seem like the user just doing more work, and that *after* having
> > read the messages. So that seems mostly backwards to me.
> 
> By the way, Outlook & Exchange suck (or at least some versions do), and
> don't seem to generate In-Reply-To and References: headers. Just got a
> mail which prompted me to write this mail. I'd really like to be able to
> join messages in a case like this.

It's actually worse than that.  I was looking into why some of my
threads weren't coalescing.  Some of it seems to be a very difficult bug
DB that doesn't use identical Message-ID's to refer to the parent bug
mail.  I don't know how that works at all.  Sometimes it uses the same
Message-ID, but sometimes it changes a number in the ID.

However, this isn't the worst news, because I work with a lot of
Exchange users, and I noticed that their mail was also refusing to
thread.

I was looking at the message bodies, and they led me to these links
about mail processing.

The problem identified:
http://blog.postmaster.gr/2007/12/11/trying-to-make-use-of-outlooks-thread-index-header/

How to read it, or how Exchange goes its own way:
http://blog.postmaster.gr/2007/12/23/more-fun-with-message-threading/

With a fairly loose understanding of how notmuch detects threads, and
how much information it places in the Xapian database (only the
msg-id?), I can't suggest much of the how.

But I would like to propose that we consider handling the Exchange
non-standard threading method as well as the RFC822 threading in the
headers.

Reactions?

-Mark