The Citadel Groupware Server

Microsoft Exchange, Meet Your Replacement

The time has come to consider moving that expensive, high-maintenance Windows system to a sleeker, more robust Linux system. The gap analyses have been done, the meetings held, the presentations complete, and now it's go time. Although installing and configuring a Linux server back end can be challenging, we all know that users aren't going to care about that. What they want is uninterrupted functionality so they can continue doing their jobs. Although migrating users from applications such as Microsoft Office to is generally an intuitive task, the 800-pound gorilla that's keeping you up at night is e-mail and groupware. How are you going to provide and manage Microsoft Outlook-like functionality to the masses? In a word, Citadel.

One of the understated wonders of the Free and Open Source Software world is the Citadel Groupware Server ( Controlled by a single developer, Citadel started life in 1987 as a UNIX version of the already-existing Citadel-CP/M application. Almost 20 years later, the modern-day Citadel boasts all of the functionality of a mature groupware server. One of the miracles that Citadel can perform is providing all of the most-used functionality of Microsoft Exchange with little fuss and and even less cost.

Many modern organizations are coming to the realization that their IT budget is largely controlled by Microsoft's licensing fees and hardware requirements. Although organizations can prepare for some of these costs, many are looking at Vista with trepidation. Although the hardware requirements for Vista aren't obscenely over the top, many organizations still will need to upgrade their hardware in order to run it. And, sooner or later, run it they will. The hardware upgrade cycle is a never-ending source of pain for some organizations, because not only do servers and server software need to be upgraded on a somewhat regular basis, but untold numbers of workstations also need attention.

Depending on the size of your organization, your Microsoft Exchange server might be the most robust server in the closet, and finding a suitable replacement for Exchange is quite often a show-stopper. Citadel is a groupware solution that allows organizations not only to avoid upgrading software, but it also runs on a significantly lower-powered machine, thus breaking the hardware upgrade cycle for years to come.

How to Get It

It's always good practice to install and test everything on a test server before moving it into a production environment. Swapping out your mail server is certainly no different, and you should keep your Citadel testing as far away from your production system as possible. Obtaining and configuring Citadel is several orders of magnitude easier with an Internet-connected server, however, because you can avail yourself of the Easy Installation process.

As of this writing, the most current version of Citadel is 6.84. I highly recommend a trip by the Citadel site in order to obtain the most current version of the server and the most current version of the installation instructions. Our testing environment consisted of Debian Sarge with a 2.6 kernel running in VMware Player 1.0.2. For no particular reason, we selected the Web server installation option, but virtually any installation category should work, as Citadel installs everything it needs. In the past, we have installed and run Citadel on a Debian Sarge server proper, and in both cases the installation was flawless.


I cover the Easy Installation method here not only because it's easy, but it's also fairly undemanding on resources and therefore quite likely that anyone can make use of it. Just about the only requirement for the Easy Installation method is a working—and preferably fast—Internet connection.

The Easy Installation method requires the toolchain, or build environment, to be present on the target platform. In addition, curl (or wget) is required. If you'd like to support SSL connections to the server, you also need libssl-dev. On a Debian system, use the following command to install or verify your build environment:

apt-get install build-essential curl libssl-dev

Before installing, it is worth noting that Citadel is designed as a black box system running on your server. Part of that black box means that Citadel authenticates logins against its own user database and not against your system user database (typically /etc/passwd). If you'd like Citadel to authenticate against your system user database, you must export the IS_AUTOLOGIN variable to the environment prior to running the Citadel install, like so:

export IS_AUTOLOGIN=yes

Now that the environment is set, it's time to kick off the Easy Install with the command:

curl | sh


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Anonymous's picture

Just tried out Citadel and I am AMAZED! When they say "Easy Install" they MEAN it! Up and running in about ten minutes. These guys have got it together.

I remember Citadel from its BBS days

Sum Yung Gai's picture

Man, we're going way back now, aren't we? I remember using Citadel and Stonehenge BBS's back in the 1980's. I just got through visiting the current Citadel Web site, and for those like me who remember the original Citadel BBS, prepare to be amazed.

But for this article, I wouldn't have known that Citadel was still alive in *any* form, and I certainly had no idea in the world that it had evolved into a full-blown MS Exchange groupware replacement!

This is something worth downloading and trying out. I used to be a MS Exchange admin before I joined the Free Software movement, and I'm definitely looking forward to trying out this new Citadel. It had a well-deserved good reputation back in the BBS days. I can hardly wait to try out its groupware features of today!

More than just a BBS

c.s.'s picture

Citadel's history as a BBS platform, combined with the fact that the Citadel developers have made an effort to try to change the way you think about groupware, leads some people to believe that the modern Citadel system is really nothing more than an overgrown BBS. But to think that way really does not give due credit to the extremely powerful capabilities of this platform.

Citadel is truly innovative -- it doesn't just try to be a feature-for-feature clone of Microsoft Exchange. The whole concept behind its design is that many of the concepts and style of user interaction that we became familiar with in the BBS world are actually quite useful in a conventional groupware scenario as well.

Using it now

riley's picture

Very true. We moved our mail server (approximately 100 users, previously running Microsoft Exchange) to Citadel, and not only does it perform flawlessly, but it really does change the way you think about groupware. Everyone else is trying to clone "Microsoft's way" but you know what, Microsoft's way is stupid. Citadel's approach is some fresh new thinking.

not only that, the community

Anonymous's picture

not only that, the community is EXTREMELY active.

just joing the mailing list to see.