Tuta’s product is snake oil.
If you don’t care about their (nonstandard, incompatible, and snake oil) end-to-end encryption feature and just want a freemium email provider which (purports to) protect your privacy in other ways, the fact that their flagship feature is snake oil should still be a red flag.
StartPage/StartMail is owned by an adtech company who’s website boasts that they “develop & grow our suite of privacy-focused products, and deliver high-intent customers to our advertising partners” 🤔
They have a whitepaper which actually does a good job explaining how end-to-end encryption in a web browser (as Tuta, Protonmail, and others do) can be circumvented by a malicious server:
However (i am not making this up!) they hilariously use this analysis to justify having implemented server-side OpenPGP instead 🤡