Furthermore, save for some nice branding color schemes, better font sizing, and maybe a few other useful UI features, an email should be almost all text and images. It should be treated more like a postal letter or a chatroom message.
A Plaintext email would show the html tags in plaintext. It’s probably not something this library wants to solve since stripping html tags from an html email isn’t necessarily a coherent plaintext email either.
Generating a plaintext message dynamically isn’t much of a pain point but html emails can be.