Internetworkers: http://www.ibiblio.org/internetworkers/

[Steven Champeon <schampeo AT hesketh.com>]

on Wed, Jul 30, 2003 at 07:56:37PM -0400, Ian Meyer wrote:
> eekers...another one...
> 
> tihs isnt a big deal, but its kinda annoying...and i posted a couple 
> weeks ago about it too
> 
> when you reply to a message, then delete the contents and change the 
> subject, it keeps (somehow) a merker in it that associated it with the 
> previous message. so when mail applications "thread" emails, it gets 
> grouped with the rest of the emails (in this case, the PAM ones).

Yes, there are two headers, 'References' (which contains the Message-Id
headers of all relevant messages in a thread) and 'In-Reply-To' (which
contains the Message-Id of the message to which the new message is in
reply).

Reply to a message with a Message-Id header of <foo AT example.com>, and
the new message will contain an In-Reply-To of '<foo AT example.com>'.
Reply to that message, let's say the reply is given a Message-Id of
'<bar AT example.com>', and the References header in your new message will
make reference to both <foo AT example.com> and <bar AT example.com>. The
Message-Id headers are supposed to be unique, as well.

It's a pretty nifty system, and works quite well, though naturally in
several major vendors' products, they have chosen to break it - and
many people who've never looked at their headers (or even know there
/are/ headers in an email message, or what they actually contain) seem
to have trouble with the concept. 

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