OT: clp threading?

[Skip Montanaro]

    Anthony> Mail-readers typically don't add a 'references' line, instead
    Anthony> using 'in-reply-to'.

VM does.  I see in RFC2822 that it's listed as "SHOULD occur in some replies
- see 3.6.4".  Section 3.6.4 just indicates

    The "In-Reply-To:" and "References:" fields are used when creating a
    reply to a message.

and then goes on to describe how to create them.  While both are optional,
there's no suggestion that "References:" should be generated any less
frequently than "In-Reply-To:".

Skip