20 Mar 2012

8 Free Open Source Alternatives To Microsoft Exchange

Many users are frustrated with the planned obsolescence and expense of Microsoft products. One of Microsoft's popular products has been Microsoft Exchange, while many users are impressed with the features of Microsoft Exchange; others are looking for open source alternatives.

Ubuntu Server

For system administrators with experience, Ubuntu Server includes a full range of features such as private and public clouds, security from AppArmor, virtualization, integration between MacOS X and Microsoft Network. The Mail Server includes SMTP, POP3, and IMAP 4 capabilities, as well as Webmail, contact sharing, file sharing, and discussion boards. Ubuntu Server is free and support options are available.


Open-Xchange comes in several versions, including a free Community version, Hosting and Server Edition, and Advanced Server Version. The Advanced Server edition allows you to work with Microsoft Outlook or MS Exchange. The Hosting version is designed for hosting services and ISPs to provide email and group services. Only the Community version is free.

Citadel Groupware Server

Citadel works by dividing elements into “rooms”, such as email, RSS, chat, and calendar. Citadel works with the Linux, BSD, Unix, and Solaris OS, and includes features such as instant messaging and support for mobile devices. Citadel is easy to install, and there is a high level of online community support.


While Horde is not specifically marketed as an alternative to Microsoft Exchange, it offers a wide range of features and modules to add-in. Horde is open source. Because of the many alternatives, it may be difficult for inexperienced users to set op, but most administration is performed via a web interface.


Kolab offers a full range of groupware features including email. Calendaring, contacts and multi-client support. Kolab works with IMAP email, and there is a plug-in available to integrate with Outlook.


Scalix is the current incarnation of HP OpenMail, and has all the bells and whistles Exchange users have come to expect, including group calendaring, PIM, email, and busy/free services. There is both a free community edition and a commercial (supported) version.


eGroupware has both a free community edition and a commercial edition. Features include task, project and event management, file server, information sharing, and website content management.


For small organizations who are primarily interested in an email server, SquirrelMail is another alternative. There are a number of plug-ins available such as shared calendars, shared to-do lists, to-do reminders, and notes, which add to the productivity of this product.

When it comes to features, Microsoft sometimes seems to have the attitude of the small town general store provider: “If we don't have it, you don't need it”. Open source solutions, on the other hand encourage tweaks and add-ons to improve both productivity and enjoyment.
Advantages of Microsoft Exchange include the user-friendly interface, security, and support (at least until the next version is released and you have to buy an upgrade.) Besides limited features and planned obsolescence, Microsoft products are more expensive than (free) open-source alternatives.

Collaboration Station
Image by Jeffrey Beall

Ilya Elbert writes for several IT Support Phoenix and Computer Repair Phoenix corporations.


  1. rondcube is what mostly get's installed nowadays instead of squirrel-mail IMHO.

  2. Wow...how can you not mention Zarafa (with Z-Push) and Zimbra. Both are replacing Exchange left and right in the Enterprise like there is no tomorrow. Scalix is too expensive compared to Zarafa and Zimbra so there seems little traction for Scalix in Europe. And Zarafa being in Europe does help their great success in Europe.

  3. Look for the new release of Kolab 3.0 due out in a few months, which has tons of great improvements: http://blogs.fsfe.org/greve/?p=470.

    Kolab is a truly open product and you get the full functionality in the community version; there are no closed bits. Most of the product development is done by a couple of commercial companies working together and providing enough resources to actually move the product forward.

    There is commercial support available too for those that need it.

  4. Check out OBM (http://obm.org).

  5. SOGo groupware is no only an excellent replacement for Exchange, but also has first class mobile device support and no costs for Microsoft Outlook connector

    1. SOGo's an *excellent* medium to large enterprise replacement for Exchange. It's a bit heavy for the SOHO and small enterprise crowd. You can certainly use it, but there's quite a few moving parts- so there's a bit of administration from time to time with it. Citadel's web interface is the only thing keeping it from fully being the low-to-mid end fire and forget solution.

      It should be noted that the SOGo connector for Thunderbird will allow you to hook into either server effortlessly and make it largely like Outlook in experience.

  6. To scale Lars' pic to 200x150 without those horrid aliasing swirls, use Gimp -
    apply Blur once (Filters.. Blur..), then Scale down (Cubic or Sinc) and Sharpen if necessary.

  7. Zarafa is the bomb, not sure how it is not on this list you can connect to it vi outlook or your web browser.

    It is not an alternative to Exchange, but a replacement.

    It's got email, calendar, tasks. etc.
    It can be configure securely wutj tls/ssl and get user data from a LDAP server.

    I tried SOGo but had some issues with it.

  8. I am not sure who burned more users and send them back to M$. Was it Kolab or Scalix ?

    Anyway - Scalix is not Open Source and dead.

    Kolab another time has great plans but asks all to wait ...

    Since we use Zarafa we are satisfied for the first time.

    1. I don't comment on my guest posts usually, but this time I can't keep silence.
      Scalix is open source. It's not GPL, but still... see p.2.1 under the link.

      Kolab's last stable release was in October 2011, which means the development continues. Pace may be not that promising, but you can better help this, instead of critisizing.


    Not talking abvout EMC/Zimbra.. You MUST be KIDDING!!!!

  10. Hi:
    Does sogo and zimbra can work with outlook (sync calendar and contacts) using exchange protocol?

    My outlook crashes with sogo, and zimbra (z-push) has no free ( or something that works) backend for outlook.

    If I need to conect outlook by using exchange from an open source project, what would be?

  11. Hi,

    What about GROUP-E Collaboration Software


  12. Scalix is NOT open source. Some few components of Scalix source are available. I am a scalix admin and have been for six years, and I have requested sources dozens of times - Florian has ALWAYS refused to supply sources. Show me the source for the Scalix PAM modules! You can put a label on something that says open source, but in the case of Scalix this is pure bullshit. Scalix could have been great, but Florian and Xandros killed it.

  13. Zarafa is the way to go. Much lighter and cheaper than Zimbra and includes all the features that for other products are considered optional.

    It scales very well from 5 to thousands of users and is available both on site or hosted.

  14. What about Group-Office groupware?

    There's an open source and a professional version at:


  15. I would suggest the Open Source project Zentyal (www.zentyal.org). Many days have past since this page was posted and times change. They managed now to be the first Native replacement for Exchange and you there is no need anymore for connectors or plugins in the outlook clients. This will save the sys admins a lot of headaches ;)