Microsoft Exchange may be one of the most used groupware products on the market but there are also many open source alternatives available.
When most businesses start out they are able to make do with a couple of email addresses and a few shared directories to get their daily work done.
But as they grow in size they usually start to look for products that will give them more features and better tools to share emails, calendars, project notes, remote email and so on.
The most obvious solution for most companies that are already using Windows is to set up a Microsoft Exchange server which offers all this and more.
There are many good reasons to install Microsoft Exchange: It is easier for system administrators to manage email accounts, add and delete users, keep email in a central repository as well as enable calendars and calendar sharing.
But, Microsoft Exchange is also expensive to buy, has a finite set of features and is not open source.
Which is why many users consider open source groupware alternatives that offer the features of Exchange without the cost and limitations. Here we look as some of the most popular of these.
Owned by Yahoo, Zimbra is one of the most popular alternatives to Microsoft Exchange and is a good example of how an open source platform can offer all of the traditional Exchange features as well as a range of additional ones.
Although there is speculation that Yahoo is looking to sell Zimbra, development of the product continues and just a couple of weeks ago version 6.0 of Zimbra Collaboration Suite was released.
In addition to providing email services, Zimbra also caters for shared calendars, contacts and wikis. Although Zimbra can be used with almost all email clients from Outlook to Evolution, one of its strengths is its own web-based email client which gives access to all of Zimbra's features.
Although web-based Zimbra's email client is not unlike Google Mail and feels like a desktop application more than a web-based one.
Users don't have to use the web-based email client, however. There is also a desktop client available as well as support for most mobile clients as well as the usual third-party clients from Thunderbird to Outlook to Apple clients.
Zimbra also supports over the air syncing to Blackberry and iPhone clients.
There is a free version of Zimbra available which has almost all of the features of the paid-for version which adds a few additional capabilities.
Horde is not traditionally marketed as an Exchange alternative but thanks to its extensive base it is perhaps the most feature-rich platform around.
Horde is essentially a PHP framework which can do just about anything from email to contact lists, shared calendaring to task lists.
The Horde framework provides the basic platform and the various modules add in wanted features.
Horde is completely open source so it is free for all uses.
As with Zimbra the best of Horde is available through the web interface, although certain amounts of its functionality can be accessed through standard email clients.
Because Horde is so open-ended with any number of features possible, it is not as easy to set up as Zimbra which is built to task.
Most administration is done through a web interface like Zimbra.
Horde is not a drop-in replacement for Microsoft Exchange but it does offer a broad range of possibilities.
Originally created for German Federal Office for Information Security, Kolab has matured over the past five years to become a full-featured groupware suite which offers a range of collaboration features from email and calendaring to room bookings and multi-client support.
Kolab uses IMAP4 to manage emails, contacts and calendaring which means that almost all IMAP-capable clients can access Kolab data and calendars can be shared between users.
Being open source Kolab supports all popular open source mail clients from Thunderbird to KDE's Kontact suite.
Outlook users can also access Kolab data using a proprietary plugin, including one available from SA-based developers Toltec.
Not unlike Horde, Open-Xchange is a groupware framework that can be enhanced with a range of modules from email to project management.
Again, most of the features are accessed through the web interface although a limited selection of tasks can be done through standard email clients.
Open-Xchange does, however, support push email for Blackberry and iPhone clients as well as document sharing through the web interface which makes it a powerful alternative to Microsoft Exchange.
Originally based on HP OpenMail, Scalix is a full-featured Exchange alternative. Like most of the servers here, Scalix also includes a web-based email client which uses Ajax to replicate the feel of a desktop application.
For those that don't want to use the web-based application most popular clients are catered for with connectors for the likes of Evolution and Outlook available.
Scalix includes support for push email, PIM, group calendaring, free/busy services, public folders, delegation, and so on, just like Exchange.
There is a free community edition of Scalix available for download or organisations with a large number of high-end users can opt for the paid-for supported version.