This is now a subchild thread (was Re: [SECURITY] Crooks, thieves, kidnappers...

[Valdis Kletnieks <Valdis.Kletnieks () VT EDU>]

On Wed, 08 Sep 2010 10:00:15 EDT, Phil Lambert said:
> Smarter?  It seems to me that a smarter mail-client developer would have
> been able to utilize the ... wait for it... "Subject" field.

Being able to structure sub-threads is very useful once a discussion gets to
several hundred postings and has sub-discussions going.  As an example, go look
at this:

http://mailman.nanog.org/pipermail/nanog/2010-June/thread.html

and look at the thread(s) "NATO warns of strike against cyber attackers" and
its children. You can see at a glance which things are replies to what, which
parts of the discussion formed a branching structure and which ones quickly
went down a rathole (40+ messages at the same indent level is a rathole ;)
You can also see where the threading got broken - all those myriad threads
were actually connected.

Now once you have a logical structure like that, all sorts of things become
possible - you can say stuff like "save, but don't display anything else in
this rathole subthread", "delete silently any further posts in this subthread",
"flag any thread that Steve Bellovin posts in as 'high priority' and override
any 'hide/delete' settings", and so on.  And yes, there have existed mail
programs that allow that sort of customization for over 2 decades now.

You can't do that sort of structured presentation while looking at just the
Subject: line. That only tells you that they have the same Subject: line.  It's
possible for two different threads to have the same subject line (consider two
different threads at a help desk, both of which are 'Subject: Wireless out in
Smith Hall'.

In-Reply-To: is slightly better, as it chains together messages that are actually
related to each other, but isn't perfect - in particular, if C is a reply to B, and
B is a reply to A, deleting B makes it impossible to work out that C is related
to A.  And I guarantee that you'll delete some of the mails once the thread
gets to several dozen posts.

The References: header allows reconstruction of the logical structure of a
corpus of mail, and figure out what replies are a reply to what else, often even
if large chunks of the messages have been deleted.

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