i'd incidentally just learned about this a few days ago, posted here (with no traction): https://news.ycombinator.com/item?id=32782944 , which in turn links out to https://simplelogin.io/blog/simplelogin-join-proton/

they have a limited free tier and a paid tier. i felt a little uneasy about the emails seemingly going through another set of servers (in plaintext?) for the filtering so i didn't sign up, but would love to hear other perspectives.