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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.

Zimbra Collaboration is an open, secure collaboration tool for email, calendaring, tasks and more. With the most innovative web application available today, Zimbra boosts the productivity of users on any desktop and dramatically reduces TCO compared to legacy platform vendors.

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

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 Source Collaboration, providing integration with your existing Linux mailserver, native mobile phone support, Outlook "Look & Feel" webaccess and stable Outlook sharing (100% MAPI).

MDaemon Messaging Server software for Windows can be deployed in virtual, hosted cloud or private on-premise environments. It is used by businesses in over 90 countries and over 25 languages worldwide.

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

hMailServer is a free e-mail server for Microsoft Windows. Its used by Internet service providers, companies, governments, schools and enthusiasts in all parts of the world.

Egroupware is a web based software for team collaboration, central data management and CRM: email client, online calendar, contact and task management, project and file management, trouble ticket system, synchronization.

Turnkey Solutions for the Enterprise Cloud

Xeams is a secure & powerful mail server for Windows, Linux, Solaris, MacOSX and other flavors or UNIX, which supports SMTP, POP3, and IMAP. It includes a powerful spam/junk filtering engine that elimates up to 99% of junk email right out of the box. The software offers a flexible approach to email, making it a very user friendly server.

Hosted Exchange solutions from Netrepid - the best hosted exchange provider. Accelerate your technology at on demand speed.

SmarterMail delivers Exchange-level email server software features for a fraction of the cost. With lower hardware requirements, superior stability and reduced maintenance costs, SmarterMail has significantly lower Total Cost of Ownership (TCO) and is the best-in-class Microsoft Exchange alternative for businesses and hosting companies.