great question. it depends on your threat model. proton doesn't even recommend itself if you are the next edward snowden. email is not the most secure medium of communication https://proton.me/blog/protonmail-threat-model

but imo it's great for most people. i both use and recommend it...especially for custom domains, unlimited access to #simplelogin and a mobile vpn with splittunneling on android.

that said, it's not best infosec/opsec to keep all of your eggs in one basket. i still use and recommend bitwarden and keepass over proton pass and i'd be keen to use #mullvad vpn more if it offered splittunneling etc