Sorry for the delay, but the answer was long enough that I turned it into a blog post instead. Feel free to try it out.

Gnus in Emacs, configured to use autocrypt.

If you like the medium I would recommend a manga called The Blue Eye of Horus: https://mangadex.org/title/14f6bd96-e062-40d6-8fd2-fc6925e54624/the-blue-eye-of-horus-the-story-of-a-queen-dressed-as-a-man

Posteo. Happy with them. For client, gnus in Emacs. Have it configured to do Autocrypt too, but almost nobody else on the planet does 🙁

Seriously, I find Gemini useful, even keep a blog on it.

archive.org is great for borrowing old books, that you probably can't get your hands on otherwise. Just need a bit of research following references to find titles to search for.