In the domain of email, unleas you're running your own mail system, there is NO SUCH THING as privacy against inspection by your mail provider. They can see (and hand over to authorities, or to anyone who pops them) anything you send or receive which is going to be cleartext unless you're PGP'ing the contents or something.
Someone who promises you privacy (Proton) is lying. On top of likely (actually in case of Proton) being cryptofash scum.