Open Source Alternatives to Microsoft Exchange and Lotus Domino

Microsoft Exchange is a messaging and collaboration platform that has quickly gained adoption among many corporate organizations, specially those who have standardized on Microsoft Windows Server for their infrastructure. It brings in one package many enterprise features including messaging (using its own proprietary MAPI/RPC protocol or open standard protocols such as POP3/IMAP and SMTP), shared calendaring, resource management, directory services (LDAP/AD) and many others. In later releases, it has added web access, mobile sync (supports Windows mobile, Blackberry, Android devices) clustering, and high availability features making it suitable for large organizations and mission-critical deployments. If deployed and integrated with other products from Microsoft‘s suite of server solutions such as Sharepoint (for collaboration, document management and workflow) and OCS (unified communications and collaboration), Exchange can be a formidable platform for any vendor to match.

Lotus Domino on the other hand has been around earlier, and is still used in many organizations who have decided to deploy corporate groupware solutions early on with Lotus Notes. Like Exchange, it is a messaging and collaboration platform but in addition is also an application development platform commonly used for forms-based or workflow applications. In recent releases, IBM has made Domino an extensible platform with document management services, portal services, unified communications and collaboration (with Lotus Sametime), and others.

Both platforms are mature and have enjoyed wide use in many corporate deployments. Lotus Domino has the advantage of being in the market earlier, while Exchange enjoys the advantage of having an excellent and ubiquitous client in Microsoft Outlook and great integration with Microsoft’s market-leading products.

However, customers looking for an alternative from the open source community or commercial open source vendors are in luck as there is now a host of choices. On top of standard messaging and collaboration features, many of them bundle a ton of other features and functionality, such as built-in antispam and antivirus, file or document management, cross-platform support (ie can often run on both Windows and Linux) and many others. In this post, I’ll try to list down the well known enterprise-ready alternatives and rate them based on their features, extensibility and adoption. Let’s get started:

  • Citadel. I got to know of Citadel from mailing lists and recommendations of some uses from message boards, forums and social networking sites. I haven’t tried Citadel but from what I was able to gather from their website, it seems Citadel has been around for a long time, making it a mature product in terms of features. It supports messaging (support for POP3/IMAP/SMTP), group calendars and address books, but in addition offers instant messaging, mailing list management, and bulletin board-style forums. It also bundles open source antispam and antivirus solutions SpamAssassin and ClamAV respectively. Notable is its support for the GroupDAV protocol (a subset of WebDAV), which makes it a great choice if you will be using open source clients as well such as Thunderbird, KDE Kontact, Evolution and others. A notable disadvantage is lack of support for syncing calendar and task information in Outlook. Lack of built-in clustering and high availability features may be a  problem for some organizations, although a knowledgeable Linux admin can compensate for this. With its support for GroupDAV and light hardware requirements, Citadel makes a great choice for organizations comfortable with open source or companies who want to extend the life of old server hardware. I would be hard pressed to recommend this for large enterprise deployments however where support, ease of use, and ease of maintenance and management are more important considerations than features.
  • Horde Groupware Webmail Edition. Horde is really a web application framework with Horde Groupware as a project showcase of what is possible with the framework. It is actually a mail client, with the mail and identity management pieces being handled by Postfix, Dovecot, Sendmail and OpenLDAP. Horde Groupware is widely used by many web hosting providers as a hosted groupware solution for customers and is bundled by some Linux distribution vendors (such as ClarkConnect) as their collaboration solution. Because of its roots as an application development framework, Horde can easily be extended and is really a collection of different integrated modules. Besides messaging, different modules handle calendaring, task management, mailing list management, antivirus and antispam (via SpamAssassin and ClamAV), along with file management, photo gallery, forums, memos, wikis and many others. Syncing data with Outlook is possible via 3rd party plugins, and it readily supports other open source clients as well such as Thunderbird, Evolution and others. My criticism against Horde is its dated User Interface versus the other choices here with their slick and snappy AJAX-powered front-ends. Another is the complicated and time consuming set up the various components (ie Postfix and others) Horde modules–admins might be better served getting a pre-packaged solution in place. Overall Horde, like Citadel, is a great choice for organizations with experienced Linux admins, who want to extend the life of old server hardware and want a feature-rich and mature solution. I would be hard pressed to recommend this for large enterprise deployments however where support, ease of use, and ease of maintenance and management are more important considerations than features.
  • OpenGroupware/InstantOGO. OpenGroupware also has a rich and long past. It was originally a commercial project which was later spun off to open source project was later spun off and called OpenGroupware. Like many here it supports messaging, group calendars and address books, scheduling and task management, support for GroupDAV, CalDAV, and LDAP out of the box, file and document management and many others. Its a pre-packaged solution and is relatively easy to set up and configure. The commercial version offers support for Outlook sync, as well as commercial support. Definitely a mature, feature-rich solution that is in many ways a good choice for midsized to large organizations.
  • Open-Xchange. Open-Xchange is a messaging and collaboration server that is OEMed by many service providers because of its rich features, slick webmail client and ease of setup and use. It supports many open standards protocols and supports Outlook sync via a commercial extension. Originally a commercial product that was bundled with Novell’s Linux Messaging product (SuSE Linux Open-Xchange or SLOX), it features messaging, group calendars/addressbook and scheduling, identity management (support for LDAP and AD), document management, portals,  and more. Recent releases highlight its social networking capabilities with the ability to share information with Social Networking sites like Facebook and LinkedIn. It will also soon feature support for mobile clients via Exchange’s Active Sync technology. The software is available as a community-supported product, a commercially-supported product, a turnkey appliance or as a hosted instance. Definitely a mature, feature-rich solution that is in many ways a good choice for midsized to large organizations.
  • Scalix. Scalix is also a relatively new player that from the get-go targetted the entreprise market early on. It was originally developed on top of HP OpenMail, and was licensed from HP. On top of standard messaging and groupware features it supports a lot of enterprise-grade functionality such as LDAP and AD support, high availability, multi-tenant management, support for Outlook sync and mobile devices, and many others. It features a nice, slick webmail client, but supports Outlook and mobile devices, on top of other open source clients such as Evolution, Thunderbird and many others. It was recently bought by Xandros and is now offered as a hosted instance, commercial turn-key product or a community-supported downloadable product. Because of its rich features, it should be considered as a contender in any enterprise deployment.
  • Zarafa. Zarafa is a relatively new player that is being marketed as a drop-in replacement for Microsoft Exchange. That means you can replace your existing Exchange installation with Zarafa and your existing Outlook clients and mobile devices wouldn’t know the difference. It supports Outlook’s MAPI protocol as well as the ActiveSync protocol for mobile devices. It has a slick webmail which mimics the look and feel of Outlook Web Access, and makes available a nice set of APIs so third party developers can integrate and sync data with the platform. Some popular open source applications that can sync data with Zarafa include SugarCRM (CRM) and Alfresco (document management). It is available in community as well as commercial versions, with some of the more advanced features only available in the commercial editions. The nice thing though is that the Outlook sync, unlike many here, is available as well in the community supported (ie FREE) version. Its rich feature set, compatibility with Outlook, ease of use and management ensures that this solution should be on the short list looking for a lower cost alternative to Microsoft Exchange.
  • Zimbra Collaboration Suite. Zimbra’s entry is the most interesting in that they really rethought the architecture and design of a groupware product. Zimbra is positioned as messaging and collaboration 2.0 with its mashup platform (via Zimlets which allow the product to share and sync data with third-party data sources and service providers) and its slick AJAX-powered webmail and offline client. On top of this, they still offer standard messaging and collaboration features, along with many high-end, enterprise-grade features (only available in their commercial product) such as LDAP and AD support, high availability, archiving, support for Outlook sync and mobile devices, and many others. Like Scalix, the company was recently bought by Yahoo and is now offered as a hosted instance, commercial turn-key product or a community-supported downloadable product. Like Zarafa, integration with other open source products exist like SugarCRM, Alfresco, Asterisk (IP-based PBX) and XMPP (instant messaging). Like Open-Xchange and Scalix, definitely should be on the short list for any midsized to large company looking at deploying a collaboration platform. Its extensibility and rich UI make it a good choice for companies looking for a platform to integrate with form-based and workflow applications making it my choice for companies wishing to look for an alternative to Lotus Domino.

Anything I missed? Let me know by posting a comment. Comments and suggestions are welcome!

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9 Responses to Open Source Alternatives to Microsoft Exchange and Lotus Domino

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  3. Nelson Huygen says:

    Our first experience with Citadel was during a time when our Exchange server had crashed, it wouldn’t come back up, and after nearly an entire day had passed, we just needed *something* online so our users could get email while we worked on fixing the Exchange server. We had Citadel up and running in about twenty minutes thanks to their “Easy Install” method, which really works!

    By the end of the week we had given up on ever getting Exchange working again. Citadel got the job done, and when the bosses found out that it was just as good *and* free, we just never switched back.

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  5. Gunnar Wrobel says:

    What about the Kolab groupware server? It packages Horde as webmail frontend and already comes with all the server side (postfix, imap, ldap) configuration. It is not only a webmail client. It is also supported by Kontact on Linux (and soon on Windows too), Thunderbird (in beta), and Outlook via plugins.

    I think the Kolab solution should remove some of the drawbacks you saw with Horde alone.

  6. Aaron R. says:

    Zimbra all the way! I’ve been working with Zimbra for a couple years now and having used Exchange for many years before that, I will say that Zimbra is BY FAR the best email product I have ever used.

    It has everything most users need, it’s cost effective, easy to manage, and offers fairly universal support for offline clients and mobile devices.

    If anyone is ever interested in a hosted version, check out http://www.specialai.com/zimbra.

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  8. zulme says:

    Hi.. I just wanna ask you about Horde email system. Is the Horde has the features as below (as i know Zimbra have all of these)?:

    – Ability to generate RSS or ATOM feeds based on the contents of the Inbox or other mail folders
    – Ability to subscribe to RSS/ATOM feeds
    – Aggregation of mail accounts using IMAP
    – Ability to subscribe to an external calendar in iCalendar (.ics) format
    – Ability to publish/export a calendar in iCalendar (.ics) format
    – Users can import calendar iCalendars (.ics)
    – Ability to embed an image as an ALE object inside a web Document
    – Ability to use different Global Address Lists for each domain
    – The eMail Solution natively includes Spam Assassin and the DSPAM filter for spam protection (can be turned on/off)
    – Native integration with Red Hat Cluster Suite, enabling N+M active/passive clustering across eMail Solution servers
    – eMail Solution Cluster management support for Veritas Cluster Server by Symantec version 5.0
    – Integration with Qmail

    Thank you.

  9. Microsoft is trying hard to compete with open source. They are feeling the heat from google apps. Amazing how they have come down with their price for a product that includes Office, Sharepoint, and even Exchange. Desperate? Maybe. But then again, it seems they have noticed the trend of the market towards cheap products in the cloud. $6 per month is pretty unbelievable. The only way to go cheaper really is free.

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