Documentation: process: Update email client instructions for Thunderbird

The instructions don't match with the current Thunderbird interface.
Clarification on using external extensions.
New information on how to avoid writing HTML emails.
Tell user to restart Thunderbird after modifications.

Tested-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Sotir Danailov <sndanailov@gmail.com>
Link: https://lore.kernel.org/r/20220715211307.9358-1-sndanailov@gmail.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/process/email-clients.rst

@@ -277,36 +277,61 @@ Thunderbird (GUI)
 Thunderbird is an Outlook clone that likes to mangle text, but there are ways
 to coerce it into behaving.
 
-- Allow use of an external editor:
-  The easiest thing to do with Thunderbird and patches is to use an
-  "external editor" extension and then just use your favorite ``$EDITOR``
-  for reading/merging patches into the body text.  To do this, download
-  and install the extension, then add a button for it using
-  :menuselection:`View-->Toolbars-->Customize...` and finally just click on it
-  when in the :menuselection:`Compose` dialog.
+After doing the modifications, this includes installing the extensions,
+you need to restart Thunderbird.
 
-  Please note that "external editor" requires that your editor must not
-  fork, or in other words, the editor must not return before closing.
-  You may have to pass additional flags or change the settings of your
-  editor. Most notably if you are using gvim then you must pass the -f
-  option to gvim by putting ``/usr/bin/gvim -f`` (if the binary is in
-  ``/usr/bin``) to the text editor field in :menuselection:`external editor`
-  settings. If you are using some other editor then please read its manual
-  to find out how to do this.
+- Allow use of an external editor:
+
+  The easiest thing to do with Thunderbird and patches is to use extensions
+  which open your favorite external editor.
+
+  Here are some example extensions which are capable of doing this.
+
+  - "External Editor Revived"
+
+    https://github.com/Frederick888/external-editor-revived
+
+    https://addons.thunderbird.net/en-GB/thunderbird/addon/external-editor-revived/
+
+    It requires installing a "native messaging host".
+    Please read the wiki which can be found here:
+    https://github.com/Frederick888/external-editor-revived/wiki
+
+  - "External Editor"
+
+    https://github.com/exteditor/exteditor
+
+    To do this, download and install the extension, then open the
+    :menuselection:`compose` window, add a button for it using
+    :menuselection:`View-->Toolbars-->Customize...`
+    then just click on the new button when you wish to use the external editor.
+
+    Please note that "External Editor" requires that your editor must not
+    fork, or in other words, the editor must not return before closing.
+    You may have to pass additional flags or change the settings of your
+    editor. Most notably if you are using gvim then you must pass the -f
+    option to gvim by putting ``/usr/bin/gvim --nofork"`` (if the binary is in
+    ``/usr/bin``) to the text editor field in :menuselection:`external editor`
+    settings. If you are using some other editor then please read its manual
+    to find out how to do this.
 
 To beat some sense out of the internal editor, do this:
 
-- Edit your Thunderbird config settings so that it won't use ``format=flowed``.
-  Go to :menuselection:`edit-->preferences-->advanced-->config editor` to bring up
-  the thunderbird's registry editor.
+- Edit your Thunderbird config settings so that it won't use ``format=flowed``!
+  Go to your main window and find the button for your main dropdown menu.
+  :menuselection:`Main Menu-->Preferences-->General-->Config Editor...`
+  to bring up the thunderbird's registry editor.
 
-- Set ``mailnews.send_plaintext_flowed`` to ``false``
+  - Set ``mailnews.send_plaintext_flowed`` to ``false``
 
-- Set ``mailnews.wraplength`` from ``72`` to ``0``
+  - Set ``mailnews.wraplength`` from ``72`` to ``0``
 
-- :menuselection:`View-->Message Body As-->Plain Text`
+- Don't write HTML messages! Go to the main window
+  :menuselection:`Main Menu-->Account Settings-->youracc@server.something-->Composition & Addressing`!
+  There you can disable the option "Compose messages in HTML format".
 
-- :menuselection:`View-->Character Encoding-->Unicode (UTF-8)`
+- Open messages only as plain text! Go to the main window
+  :menuselection:`Main Menu-->View-->Message Body As-->Plain Text`!
 
 TkRat (GUI)
 ***********