Open source Webmail

Mailpile

Mailpile is a modern, fast web-mail client with user-friendly encryption and privacy features. Mailpile places great emphasis on providing a clean, elegant user interface and pleasant user experience. (AGPL)

Cross-platform

RoundCube

RoundCube is a webmail client written in the PHP programming language. (GPL)

Cross-platform

Tutanota

Tutanota is the end-to-end encrypted mail client that enables you to communicate securely with anyone. Tutanota automatically encrypts all your data on your device. Your mails as well as your contacts stay private. (GPL)

Cross-platform

3 applications