Roundcube - Web-based IMAP email client
Zimbra - Zimbra is trusted by over 500 million users to increase productivity with a complete set of collaboration tools while maintaining total control over security and privacy.
Mailo - Mailo is an email client where you can send and receive emails to and from anyone with an email address.
Cyrus IMAP - The Cyrus IMAP server differs from other IMAP server implementations in that it is generally...
Mailpile - Mailpile is a modern, fast web-mail client with user-friendly encryption and privacy features.
HEY - Email at its best, new from Basecamp.