Re: Mail List Posting Guidelines

["Robert Holmgren" holmgren@xxxxxxxx]

Let me try to clarify/simplify how threading works.

Threading looks first for either or both of two headers in a received message:
"In-Reply-To: [Msg-ID]" and/or "References: [List of threaded Msg-IDs]". If
either or both of those headers are present, then the Subject of the
**referenced Message-ID[s]** -- i.e. of the msg[s] you're replying to --
determines the thread in which your current message is placed, no matter what
the Subject of your own reply may be. In other words, if In-Reply-To or
References is present, your current Subject is ignored, and threading mirrors
exactly the chain of message IDs. Most Email clients generate In-Reply-To and
Reference headers when you hit the Reply button -- the formal Email spec (RFC
821) insists upon it.

HOWEVER, if no "In-Reply-To" or References" header exists in your message, then
threading attempts to locate your current reply within an existing thread
bearing the same Subject (if alphanumerically IdEnTiCaL!). If no such thread
exists, then your msg initiates a new thread (which may, or may not, have
followups). In other words, the Subject suddenly acquires importance, whereas
in the presence of In-Reply-To or References the Subject is ignored.

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Robert Holmgren
holmgren@xxxxxxxx
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