Zimbra Collaboration Suite!

Roundcube webmail is a browser-based multilingual IMAP client with an application-like user interface. It provides full functionality you expect from an e-mail client, including MIME support, address book, folder manipulation, message searching and spell checking. Roundcube's most prominent feature is the pervasive use of Ajax technology.

Kolab is entirely Free and Open Source Software (a.k.a. FOSS), and uses Open Standards. We’ll get to why this is important to us, and hope that it is important to you thereafter.

Kolab Now, formerly MyKolab, is a fully featured secure collaboration and communication service that is easy to use on any device.

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

mailcow is a mail server suite based on Dovecot, Postfix and other open source software, that provides a modern Web UI for administration.

Microsoft Exchange Server is a messaging and collaborative software product developed by Microsoft. It is part of the Microsoft Servers line of server products and is widely used by enterprises using Microsoft infrastructure solutions. Exchanges major features consist of electronic mail, calendaring, contacts and tasks; support for mobile and web-based access to information; and support for data storage.

Open-Xchange Server 6 is the most advanced Linux based Groupware solution f.Open-Xchange Server 6 is superior in the following areas:• Open-Xchange Server 6 offers most comprehensive Groupwarefunctionality based on modern user interface technologies and includesemail, calendaring, contact management, intelligent document sharing,“smart linking” and much more.• The architecture is designed for deployment in the hosted market.• The architecture is designed for enterprises market

Full featured solution for your Email server. Native implementation of last anti-SPAM metods, webmail and easy administration included.

Axigen is a premium, all-in-one email, calendaring and collaboration platform, based on an innovative, proprietary technology, providing unmatched manageability for system administrators. Integrating all modules in a robust messaging solution, Axigen is developed for demanding users, from small businesses to large service providers.

Atmail webmail system offers a webmail client, email server platform and mailserver appliance for Linux, Unix and Windows.

Kopano puts an email, video meetings, calendaring, and file sharing solution within one single interface.