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Review: 6 free email servers for small business

hMail Server (Windows only) comes in first, Citadel (Linux only) is a close second

By Susan Perschke, Network World
September 17, 2012 07:05 AM ET

Page 6 of 7

SmarterMail can integrate with spam solutions such as SpamAssassin and Trend Micro, but it can also be configured to use other methods such as black/grey/white listing, custom headers, SMTP blocking, SPF and others.


Zarafa is maintained by a group in the Netherlands which specifically markets its collaboration server as an alternative to Microsoft Exchange. It features an AJAX based browser-based client with a PHP backend intended as replacement for Outlook. Zafara claims to be the only open-source collaboration platform with a MAPI-based architecture. Zarafa leverages existing open source technology such as Postfix as its MTA and stores all data in a MySQL database.

Zarafa runs on several Linux flavors such as Debian, SUSE, Red Hat and Ubuntu. We chose Debian Version 6.05. As the user manual states there are a 'bunch of requirements' that need to be met such as installing MySQL, Apache (or other PHP web server) and an SMTP server such as SendMail or Postfix. Installing a LAMP stack accomplishes a bulk of these prerequisites. Zarafa can be installed in four ways (distro, install scripts, manual and from source). We decided to use the install script, which, at least for our single server test, turned out to be the shortest route.

The Zarafa server is configured by a using a system-wide .cfg file. Users are typically set up using the DB plugin or if you wish to integrate with the Linux server you can use the Unix plugin. You can also manage users by using the LDAP protocol to link to solutions such as Active Directory or eDirectory.

Although Zarafa offers several commercial versions of their server, we found the open source version to be quite capable even if it lacks some of the features of its commercial counterpart (calendaring, unlimited Outlook clients and multi-server support).

Communication between the client and server is based on Simple Object Access Protocol technology. In order to communicate with mobile devices, Zarafa uses what it calls Z-push. Z-push is an open-source implementation of Microsoft's ActiveSync protocol and it works with devices running iOS, Android, Windows Mobile, Nokia and others.

The Z-Merge framework enables developers to integrate Zarafa WebApp easily with CRM, DMS and other solutions. For instance Zarafa can integrate with SugarCRM and recently a Dropbox plug-in was made available.


Citadel has its roots as a bulletin board system platform from the early 1980s, but has since developed into a groupware product with support for features such as calendaring, addressing and instant messaging in addition to email. Unlike most, if not all, other open source mail servers, Citadel is a custom purpose-built product.

For instance, it does not use Postfix, but it has its own custom code written in C for SMTP purposes. The company targets SMBs looking for a self-contained, low maintenance and fully integrated stack.

We installed Citadel on a server running Debian 6.05 and found it was easy to install compared to some of the other Linux products we'd been wrestling with. Management is browser-based and can be customized to display only the functions you wish to use. After creating a test domain, we set up users, which can be completed with a short two-step wizard, or manually.

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