thunderbird HTML editor

Thunderbird HTML editor.
This add-on adds a HTML tab to the composition window where you can see and edit the HTML source of the message.

download xpi file : https://addons.thunderbird.net/en-US/thunderbird/addon/thunderhtmledit/

update 2023-08 :
download new version via : www.betterbird.eu/addons/ : thunderHTMLedit-3.3.0.xpi
existing must be uninstalled
install via method 2 , zie [[thunderbird extention architecture#management]]