Re: I-D Recommendations for Automatic Responses to Electronic Mail

   From: Marc Mutz <mutz(_at_)kde(_dot_)org>
   Date: Tue, 2 Jul 2002 10:45:38 +0200
[...]
   The "problem" is that some mailers (e.g. KMail) depend on in-reply-to to 
   thread messages. Yes, kmail should use References, too, but...
   One of the problems is that the IMAP fetch envelope command only returns 
   in-reply-to, not references:
[...]
   And fetching the envelope structure (or ALL) is so much faster than even 
   (ALL BODY[HEADER.FIELDS (REFERENCES)])

Actually, plenty of IMAP servers (such as the Cyrus-derived ones) will
return References with approximately the same speed as ENVELOPE
information, since this information is cached in the same place.

   So it should be "SHOULD" for both "references" and "in-reply-to".

   BTW: The only misuse of In-Reply-To I've seen is from early versions of 
   mutt 1.2.x or 1.3.x.

Check http://www.jwz.org/doc/threading.html for a good discussion of
the zillions of variations of In-Reply-To. We really should be pushing
people towards References.

Larry