ProtonMail is located in Switzerland and all of their user data is protected by strict Swiss privacy laws. Additionally, all emails are secured automatically with end-to-end encryption so nobody- not even ProtonMail employees- can read your emails.
Tresorit feels like any other cloud storage service you're familiar with, except all data is encrypted before it leaves your device. You're protected from hackers, scammers, and government agencies due to their encryption and Swiss privacy laws.
Based in Germany, Tutanota is open-source, encrypts all data on your device, and offers end-to-end encryption keeping your messages, contacts, and subject lines completely private from hackers and foreign governments.