Re: Rmail: toggle between summary and message buffers

[Eli Zaretskii]

> Date: Fri, 21 Jun 2019 09:00:49 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> 
> Don't use "C-c C-c".  Use "C-c C-s" instead, and have a separate frame
> for the *mail* buffer where you compose and send email.  Then Emacs
> will not mess up your windows in the Rmail frame.

Btw, a nice side effect of this arrangement is that the next 'm' or
'r' will reuse the frame showing the *mail* buffer, so just let that
frame hang around, to be used for composing and sending email
throughout the entire session, with no need to switch to any buffer in
your other frames.