Brilliant! Rated 5 out of 5 stars

I don't take time to review typically, but this is a fantastic add-on, esp. for developers, researchers, and lots of folks who'd rather have full control over the layout of their HTML e-mails and don't have time to mess with 1/2-baked HTML editors and clunky toolbars. I have wondered for years now why not more e-mail clients would embrace this feature.
I would vote for adding support for **Markdown Extra** syntax, for tables, footnotes, ToC and abbreviations -- but it's a great functioning add-on as it stands.
Thank you to the author.

This review is for a previous version of the add-on ( 

Thanks, and Markdown Extra

Thanks a lot for the review!

Markdown Here depends on Marked.js for Markdown rendering, so support would have to be added to it for Markdown Extra. There is an issue for it ( discussing exactly that. Fingers crossed.