On Thu, Aug 27, 2026 at 10:58 +0800, Kevin J. McCarthy wrote:
This reuses the existing Mutt functions to set references, which means
they are like reply references: the full list. It clears out the
In-Reply-To header afterwards, because I personally feel like that
header is a step too far for a "forward".
So In-Reply-To: is for a reply, but References: is for something else?
Apparently that was true in 1982, when RFC 822[1] was published -- but
that something else was not defined. Maybe it hadn't been invented yet.
Here's everything that RFC 822 says about those two headers:
4.6.2. IN-REPLY-TO
The contents of this field identify previous correspon-
dence which this message answers. Note that if message iden-
tifiers are used in this field, they must use the msg-id
specification format.
4.6.3. REFERENCES
The contents of this field identify other correspondence
which this message references. Note that if message identif-
iers are used, they must use the msg-id specification format.
By 2001, when RFC 2822[2] was published, References: had evolved to:
The "In-Reply-To:" and "References:" fields are used when
creating a reply to a message....the "References:" field may
be used to identify a "thread" of conversation."
In 2008, RFC 5322[3] still had exactly that paragraph from RFC 2822.
So for at least the last 25 years, and probably since Mutt came into
existence, References: has been a path through a thread of replies. Far
as I know, nothing else was ever implemented.
-------------
[1] <https://www.rfc-editor.org/info/rfc822/#section-4.6>
[2] <https://www.rfc-editor.org/info/rfc2822/#section-3.6.4>
[3] <https://www.rfc-editor.org/info/rfc5322/#section-3.6.4>
