Top 5 Open Source Alternatives to Microsoft Exchange


By Carla Schroder | Published on: 04-May-11

Are you tired of overpaying for the Microsoft Exchange messaging server? The Linux and Free/Open Source world 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.

Five Open Source Microsoft Exchange Killers

1. Ubuntu ServerThe 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.

2. Citadel Groupware ServerCitadel 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.

3. Open-XchangeOpen-Xchange server 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 Debian Linux-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.

4.ZimbraThe Zimbra collaboration suite is another commercial many-bells-and-whistles, open source-based server with proprietary add-ons. It includes all the usual goodies: email, Webmail, shared folders, shared contacts, calendaring and scheduling, instant messaging and mobile devices, plus Outlook sync.

Zimbra’s Web interface is called Zimbra Desktop. Zimbra Desktop supports all of Zimbra’s features, and it supports syncing external accounts such as Gmail, Yahoo, or any POP3 or IMAP mail. In fact, a feature common to all of the groupware suites in this article is they have excellent Web-based client interfaces, so you don’t need standalone clients like Outlook or Evolution. If you can wean users away from their beloved Outlook you can make administration a lot easier, and not have to hassle with the cost of using special Outlook connectors.

Zimbra has Zimlets, which is their name for mashups, which is another name for usefully-collating multiple sources of information. This lets you do things like check your calendar, set appointments, and pick a restaurant to meet in without ever leaving the email you’re reading. Zimlets make a lot of information available on mouseovers such as phone numbers, flight schedules, status messages, maps, address books entries, and lots more. (A picture is worth a thousand words, so check out the demonstration video.) There is a whole gallery of Zimlets to choose from, and you can write and share your own.

SOGoThe historical stumbling block for replacing MS Exchange has been Microsoft’s closed, proprietary MAPI protocol. In 2007 the European Union ordered Microsoft to open several of its protocols such as CIFS (Common Internet File System), MS Active Directory protocols and MAPI. When Samba 4 is released it will have full support for the Microsoft protocols, providing an Active Directory alternative. MAPI is key to natively supporting MS Outlook, and to interoperability between Exchange and other groupware and mail servers.

The OpenChange project has been developing a portable open source implementation of MAPI, with the goal of native Exchange and Outlook support, and you can see this in action in the SOGo groupware suite. SOGo supports multiple languages, and multiple clients such as Outlook, Thunderbird, Blackberry, iPhone, and Android. SOGo is Free software and free of cost.

5. ZarafaZarafa, based in the Netherlands, also offers native Outlook support. Zarafa is designed to add on to your existing mail server and WebDAV server. An easy way to get acquainted is to set up a Fedora Linux test server, because Zarafa is included in Fedora.

What Sets Linux Groupware Servers Apart?

When you do a Web search for “linux groupware servers” you’ll find many more, such as Scalix, Horde, eGroupware and Kolab — all with similar feature sets. Underneath you’ll find much of the same software, such as Postfix, Dovecot, Apache, PHP, MySQL, Squirrelmail, OpenWebmail, Courier and Linux. The differences are in integration and polish, ease of installation and management, support for proprietary devices or protocols, support for extensions (like Zimlets), and licensing and support costs. It is a feast of good choices.

Carla Schroder is a system and network administrator and author of The Book of Audacity, Linux Cookbook, Linux Networking Cookbook and many how-to Linux articles.

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