Top 5 Open Source Alternatives to Microsoft Exchange

Are you tired of overpaying for the Microsoft Exchange messaging server? The Linux and Free/Open Sourceworld is cram-full of robust, capable alternatives that won’t drain your bank account. This tasty assortment ranges from free with community support, to full commercially-supported products.

5 Open Source Microsoft Exchange Killers

Ubuntu Server

The popular Ubuntu Linux, famous for its polished, easy-to-use desktop version, also has a specialized Ubuntu server edition. This is more than a re-packaged Ubuntu Desktop; it comes with a kernel tuned for server duties, a full complement of server software and no graphical interface. This is a serious, lean mean server operating system.

Ubuntu Server does little handholding, so it’s not for novice system administrators. Rather, it is for the experienced sysadmin who wants maximum control. It includes a number of enterprise-ready features such as AppArmor for security, private cloud, public cloud, high availability, a Landscape client for systems management, Mac OS X and Microsoft network integration, and virtualization.

The installer serves up a number of useful package groups such as Virtual machine host, Samba file server, LAMP stack, Printer server, and Mail server. The Mail server group installs Postfix (SMTP), and the excellent Dovecot for POP3 and IMAP4, which is a stout foundation for an on-site email server. Then add whatever additional services you want, such as a Webmail server, calendaring, shared contacts, discussion boards, file shares, and so on. Or you can install a prefab groupware suite on it.

Ubuntu Server is free of cost, and various commercial support and systems management options are available.

Citadel Groupware Server

Citadel is free of cost and 100 percent Free software, comprised entirely of GPL-licensed code. [For the uninitiated, software that’s “Free” means it’s unrestricted — you can modify the code to suit your needs. This kind of software is sometimes also referred to as “Open Source” software. Software that’s “free” (note the lower case “f”) means it’s gratis and won’t cost any money.]

Citadel is an all-in-one messaging and collaboration server that runs on Linux, BSD, Solaris, and pretty much any Unix-like operating system. It includes email, group scheduling and calendaring, shared contacts, mail list server, instant messaging, public folders, and mobile device support. Citadel supports distributed installation across multiple servers for scaling and high availability, Web access and local clients.

The key to understanding how Citadel works is grasping the old Bulletin Board Services (BBS) concept of rooms. A room is any Citadel element: email folder, RSS feed, calendar, chat — anything at all. It’s an easy installation, since it is included in most Linux distributions, and it’s easy to administer — you can literally be up and running in an hour.

There is good community support for Citadel, and there is just one version — their best one.


Open-Xchangeserver serves up several versions: the free Community edition, the Advanced Server edition and the Hosting and Server version. The Community edition is not supported by Open-Xchange, and doesn’t include proprietary modules like OXtender for MS Outlook and OXtender for Mac OS. If you want those modules, then you have to buy one of the other editions. Otherwise it’s similar to the commercial versions.

The Advanced Server is a complete system that includes the DebianLinux-based Univention Corporate Server operating system, and a raft of nifty tools such as the Open-Xchange Microsoft Outlook Uploader (for migrating data from Outlook or an MS Exchange server), the OXtender for Mobile Web, and an MS Outlook updater. If you have a lot of Microsoft clients, or you need to interoperate in a Microsoft network, the Advanced Server makes it fairly painless.

The Hosting Edition is for ISPs and hosting services that want to offer hosted email and groupware services.

Open-Xchange is a member of Lisog, the open source stack initiative, with the goals of helping businesses craft open source strategies, and integrating propriety and open source software.

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