Help & Support Register Login

Open Source alternatives to Microsoft Exchange

Those looking for an email or groupware server have many alternatives to Microsoft Exchange including Zimbra, Horde and Open-Xchange. This article looks at some of the Free and Open Source alternatives and offers advice on how to choose the best groupware product for your needs and budget.

By Iain Roberts 


Most small organisations start off with simple email accounts - downloaded emails to PCs - or use common web-based email services such as Yahoo mail. As organisations mature, they often find a need for extra features. Some choose Microsoft Exchange, but that is far from being the only choice. This article looks at some of the Free and Open Source Software alternatives which, depending on your needs, may be more cost-effective and offer more functionality. The generic term for software that adds extra features on top of basic email is “groupware”.

What do you want from groupware?

As an organisation grows larger, it typically moves to more sophisticated systems. Benefits can include:

  • Keeping emails on the central server, allowing access to all emails at anytime, from anywhere.
  • Backing up emails. With so much critical information being held in emails these days, losing them can be a real problem. 
  • Control over accounts. Being able to create, delete and change accounts and mail groups can make everything work much more smoothly.
  • Shared access, for example by delegating your email or giving others read access.
  • Shared calendars, so people can book meetings, check everyone's availability and allow others to access their calendars.
  • Extra features such as document management, tasks, project management, shared bookmarks, wikis and forums (not all packages have all of these).

Factors to consider when buying

  • Implementation and support: Email/groupware servers can be complicated beasts. The good ones try hard to hide as much complexity as possible, but sometimes you can't sensibly make things simpler. Make sure that you get advice from people with experience of the groupware product you plan to run.
  • The product community: The Open Source products listed here all have strong communities around them: people who use them or write the software themselves and can answer questions. Should you wish, you can become a part of that community, helping others and influencing the future development of the software.
  • Features: It might sound obvious, but more features doesn't always mean better. If there are features you don't expect to need, don't consider them. Think about what you want a groupware server to do for you and see where the best match is. Some servers make it easy to add on new features, so it's worth considering that if you are not sure what you will need.
  • Price: Some products have no licence fee at all, some have a free basic version and a licensed advanced version with additional features. Remember, though, that the licence fee is probably a small part of the overall cost over the life of the system. There is also hardware, implementation, support, training and upgrades. Check the licensing costs as your organisation grows: how much more will you have to pay?
  • Training: All the systems we look at here have simple, intuitive web interfaces and work with most common email clients. Nearly anyone familiar with email will be able to manage the basics with virtually no training and, for normal users, half a day's training would be sufficient to cover the advanced features of any of the systems.
  • Licence terms: Most of the products mentioned in this article come with a Free or Open Source licence. That means you can install them on as many systems as you like, have as many users as you like, change the software yourself and give it away to others. Proprietary software such as Microsoft Exchange puts many more restrictions on what you can do and it makes sense to be aware of those.

Email clients and servers

The client is the piece of software users interact with every day. Microsoft Outlook and Thunderbird are examples of email clients. The server holds all the information and communicates with the client, not directly to the end user.

All groupware server products have a small number of preferred clients (often just one) through which everything will work correctly (for Exchange you need Outlook, for example). You can normally use different clients but you may lose some of the functionality. Of course, no-one uses every feature anyway so as long as your preferred email client supports the functions you want to use, there's no problem.

Do not be frightened to switch email clients. You might think that users will have trouble learning a new product, but that's rarely the case. We're used to using complex web applications like Amazon, eBay and MySpace; using an intuitive web-based email client is no harder.

Where to locate your server

The obvious solution might be to buy a server and put it in your office. For some, that will be the best option, but there are several others that might suit you better.

  • If most of the people who use the server are based in your office and you or your support people are happy to manage the system, keeping it in-house might be best. Do consider the implications of fire or theft though: having backups held at another location could save your organisation.
  • Where users often access your server from outside your office, it might make sense to have the system hosted at a professional data centre. Not only will access be much faster (as users won't be coming in through your broadband connection), the data centre is likely to be a good deal more secure than your office.
  • Consider whether you need a whole server yourself at all. There are plenty of hosted services where you rent accounts on a server someone else manages. You can rent a whole email domain, giving you nearly all the flexibility with fewer headaches and often a lower price tag.

Open Source Groupware servers

Groupware servers have features to enhance collaboration including calendars, address books, news readers, wikis, forums and shared bookmarks. Some have more than others, so be sure to consider what you want.

The two most widely-used proprietary groupware servers are Microsoft Exchange and Lotus Domino (for which the client is Lotus Notes). Let's have a look at some Open Source alternatives.


In addition to email, Zimbra Collaboration Suite includes shared calendars, contacts and a wiki functionality. It comes in an Open Source version which can be downloaded for free and a Network Edition which has a licence fee along with extra features such as an Outlook 2003 connector and online backup.

Zimbra can be used with almost any email client, but its own web client has been maturing fast and will be preferred by many. Logging onto Zimbra via your web browser gives you access all of Zimbra's features and the interface (similar to Google Mail) gives it the feel of a normal desktop application.

Administration is another Zimbra strong point: nearly all is done via another web interface. Upgrades are simpler than for any other similar product I have come across.

At least two UK companies offer a hosted Zimbra service including Simply Mail Solutions.


Of all the products looked at here, along with Microsoft Exchange, Horde has the greatest functionality. It covers email, contacts, calendaring and tasks lists and does a lot more besides, with modules covering shared bookmarks, project management, time recording/billing, WAP mail client and wiki. Horde is also fully open source, meaning no licence fees for any of the modules. Horde also has very advanced access controls, giving a great deal of control over which users have access to which information.

Some features of Horde are accessible through all standard email clients but, as with Zimbra, getting the most from Horde means web-browser access.

Like Zimbra, administration of Horde is nearly all through your web browser. Installing and upgrading Horde is somewhat more complex, though, and definitely something to be done by someone experienced.


Like Horde, Open-Xchange is a modular groupware system with a web interface (again, email clients can be used for some functions). It links in well with other software (e.g. via LDAP and WebDAV). Additional modules include document management (with version control and locking) and project management (include Gantt charts and tasks). The web interface is not quite as nice as Zimbra's, but is easy to use and does the job.

Open-Xchange has an unsupported version and a supported version which includes extra features. The differences between the two are significant and the unsupported version of Open-Xchange is complex to install.

Other options

There are several other alternatives which are well worth a look.

For more groupware choices, take a look at Kolab, Scalix, eGroupware, Citadel or OpenGroupware.

If you just want email, but want to keep your mail on a server and make sure it is properly backed up, take a look at SquirrelMail, renowned for its reliability and offering a web client along with support for mainstream email clients.

Small office servers, which bundle together groupware with other functions such as file storage, web server and telephony also exist in the Free and Open Source Software world.

About the author

Iain Roberts

Axiom Tech

Creative Commons LicenseThis work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 2.0 UK: England & Wales License.