ProBinder - ProBinder is your secured online teamwork platform to manage all of your work simply and securely.
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.
Collanos - Collanos Workplace is a proprietary teamwork software that ceased development in 2010.
iRedMail - A fully fledged, free email server solution, an open source project (GPL v2).
Projectfusion - Projectfusion is a virtual data room system that offers enterprises a single and centralized platform from which to set up data rooms, manage projects, collaborate and perform file sharing securely.
mailcow - An open source mailserver suite.