A thorough explanation of (almost) automatically converting your markdown-written mails into both plaintext (keeping the markdown) and html versions and send both as alternative mime types.

That will display html for those clients who can and fall back (or prefer) plaintext for those who don't want to (e.g. neomutt commandlines).

Uses a manually invoked macro (by pressing a letter before sending the mail) to convert the message though I wonder if it could be done automatically through e.g. a send-hook