Update the manual about composing format=flowed messages

mu4e/mu4e.texi

@@ -3840,21 +3840,19 @@ don't have it, your mails mostly look quite bad especially on mobile
 devices) and here's the RFC with all the details:
 @url{http://www.ietf.org/rfc/rfc2646.txt}.
 
-To add this to outgoing mu4e emails, activate @t{use-hard-newlines} and
-use only @t{M-q} or @t{fill-paragraph} for your paragraphs, Emacs
-indicates intra-paragraph breaks with soft newlines and inter-paragraph
-breaks with hard newlines. When the Gnus code sees these on outgoing
-emails, it automatically sets @t{format=flowed}.
+Since version 0.9.17, @t{mu4e} send emails with @t{format=flowed} by
+default.  The transformation of your message into the proper format is
+done at the time of sending.  In order to happen properly, you should
+write each paragraph of your message of as a long line (i.e. without
+carriage return).  If you introduce unwanted newlines in your paragraph,
+use @kbd{M-q} to reformat it as a single line.
 
-To enable this, you can use something like this in your init.el:
+If you want to send the message with long lines but without
+@t{format=flowed} (because, say, the receiver does not understand it as
+it is the case for Google or Github), use @kbd{M-x use-hard-newlines} or
+uncheck the box @t{format=flowed} in the @t{Text} menu when composing a
+message.
 
-@lisp
-;; tip submitted by mu4e user cpbotha
-(add-hook 'mu4e-compose-mode-hook
-          (defun cpb-compose-setup ()
-            "Outgoing mails get format=flowed."
-            (use-hard-newlines t 'guess)))
-@end lisp
 @end enumerate
 
 @node Known issues