Maidir leis an mbreiseán seo
(there will be no more updates, I can't keep up with the changes in Thunderbird).
This extension allows for quick use of HTML files or online links (http or ftp) as templates for messages, both for composing new messages and replies. Up to 9 templates can be configured and recalled both through menu options as well as keyboard shortcuts.
Template definitions may include fields for the replied message (in case the template is used for a reply) and also attachments.
Forked from https://freeshell.de/~kaosmos/templateloader-en.html (which seems it is not longer in development)