bug#28266: 25.2; RMAIL FCC coding issue

[Charles A. Roelli]

> Date: Fri, 22 Sep 2017 16:13:58 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> 
> I cannot reproduce this with the current emacs-26 branch tip.
> However, in my case, Emacs asked for a suitable coding-system each
> time I wanted to send a message.  Answering UTF-8 produced a valid
> encoding in both cases.
> 
> So perhaps the difference, and the reason for a problem you see, is
> the default encoding in your case, which you didn't show.  (In my
> case, the default is Latin-1.)

Hmm, I was never queried for a coding system.  I've repeated the issue
on GNU/Linux with 25.3 and macOS with 25.3 and emacs-26.  And I don't
set any special locales/language environments:

> Important settings:
>   value of $LANG: en_GB.UTF-8
>   locale-coding-system: utf-8-unix