FastMail - Email, calendars, and contacts to highest standards of security, privacy and reliability.
InstAddr - Disposable email address application.
ProtonMail - Secure email with absolutely no compromises. Get your free encrypted email account today.
Horde - Horde Groupware is a free, enterprise ready, browser based collaboration suite.
Mailfence - Easy to use end-to-end encrypted email. Secure and private email.
Mailo - Mailo is an email client where you can send and receive emails to and from anyone with an email address.