Customizing editor

The default configured editor is gvim embedded using XEmbed, but any editor or setup that support XEmbed can in principle be used.

The editor.cmd string is passed to ustring::compose, and the following arguments must be set:

filename: %1
servername: %2 (probably optional)
socketid: %3

Editor suggestions

gvim (default)

gvim -geom 10x10 --servername %2 --socketid %3 -f -c 'set ft=mail' '+set fileencoding=utf-8' '+set ff=unix' '+set enc=utf-8' %1

fancy gvim with Goyo and Limelight:

gvim -geom 10x10 --servername %2 --socketid %3 -f -c 'set ft=mail' '+set fileencoding=utf-8' '+set enc=utf-8' '+set ff=unix' -c Goyo -c Limelight! %1

emacs

emacs --parent-id %3 %1

Pro-tip: use notmuch-message-mode

You can use the notmuch-message-mode for composing email in emacs by having this in your emacs config file (replace @localhost with your machine's hostname):

(require 'notmuch)
(add-to-list 'auto-mode-alist '("\\@localhost\\'" . notmuch-message-mode))

neovim (through st)

st -f 'Monospace' -w %3 -e nvim %1

the st terminal is suggested since it supports XEmbed.