Hey man, email existed before google :) You can use whichever email service you want that's not google and use an open source email client like K-9 Mail or AOSP

Hey man, email existed before google :) You can use whichever email service you want that's not google and use an open source email client like K-9 Mail or AOSP's Email client :) Only non-standard emails won't work with POP3 or IMAP protocols. In those cases you need to use their specific program/protocols, yes. It seems Tutanota falls in this category, as does ProtonMail.