Squirrelmail

SquirrelMail is a standards-based webmail package written in PHP.

Afterlogic Webmail

Webmail is an open-source webmail script for existing IMAP servers.

All your E-mail, from all your accounts, in one place. Cypht is like a news reader, but for E-mail.

Horde Groupware is a free, enterprise ready, browser based collaboration suite.

Kolab Groupware is a secure, scalable, reliable, flexible, full-featured collaboration suite.

Mailpile is a modern, fast web-mail client with user-friendly encryption and privacy features.

Mailspring is a mail client for Mac, Windows and Linux.

Starting with version 0.9.8, mu provides an emacs-based e-mail client which uses mu as its back-end: mu4e.

Self-hosted server for the ProtonMail client.

Organize your world. Outlook’s email and calendar tools help you communicate, stay on top of what matters, and get things done.

Web- and IMAP-based email service. 2GB cost 1€/month.

Secure email with absolutely no compromises. Get your free encrypted email account today.

RainLoop is a web based email client.

Web-based IMAP email client

SOGo is groupware server with a focus on scalability and open standards.

Get your encrypted mailbox for free.

Open Source WebMail Lite is a free community edition of full-featured WebMail Pro server applicatio…

Zimbra Collaboration is an open, secure collaboration tool for email, calendaring, tasks and more.

Zoho Mail is a webmail service built with the needs of a modern business in mind.

A fully fledged, free email server solution, an open source project (GPL v2).

An open source mailserver suite.