Sympa

RainLoop is a web-based email client.

Apple iCloud Mail is a sleek, user-friendly webmail service integrated into Apple's ecosystem. It offers seamless synchronization across Apple devices, robust spam filtering, and generous storage options, making it an ideal choice for Apple users seeking a streamlined email experience.

CrossBox is a webmail client.

Proton Mail is a privacy-focused email service that prioritizes security and user confidentiality. With end-to-end encryption, zero-access encryption, and Swiss privacy law protection, it offers a secure communication platform for over 70 million users across web and mobile platforms.

SquirrelMail is an open-source web-mail package that is based on PHP language. It provides a web-based-email client and a proxy server for IMAP protocol.