bug#40561: 27.0.90; Mail-related errors in docstrings and manuals

[Jorge P . de Morais Neto]

Em [2020-04-12 dom 21:34:13+0300], Eli Zaretskii escreveu:

> I use Rmail.  It has only one command: rmail-replay.  It uses these
> headers according to the precedence described in the manual, AFAICT.
>
> Maybe Gnus has more "reply" commands, but Gnus has its own manual.

Gnus may have its own manual, but still including that brief information
in Emacs' manual would help not only Gnus users, but also users of
Notmuch and possibly also other popular clients, so it would have good
cost-effect.  Besides, it would help users understand what effect will
`Mail-Followup-To' likely have on the recipient when he replies to a
message sent by the Emacs user.

I am sorry for insisting so much, so if you still think the manual is
clear here, then I will silently accept.

Regards
-- 
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