The Open-Source Outlook Connector Project


If you believe you can fund a part time developer for this project please contact us. We are open to a commercial partnership to continue the development of the Outlook Connector.

The "Open Connector" Project aims to develop extensions for Microsoft Outlook® email and groupware client. These open-source extensions, or add-ins, allow Microsoft Outlook®'s full functionality with email and calendar servers; including groupware servers other than Microsoft Exchange®.

Please watch our Demo Video.


Fig 1. Microsoft Outlook with Open Connector message store loaded and highlighted in red

If you are familiar with MAPI service providers, or just MAPI in general and would like to help, please join the otlkcon-devel mailing list.

Alternatively, you can consider Donating to the Open Source Outlook Connector project to help offset the cost of developer time. If you believe that you would like to otherwise help with funding this project please contact us.


A set of Extended MAPI DLLs written in Visual C/C++. Our initial targets are a MAPI Message Store Provider and a MAPI Transport Provider.

Project Goals

Develop a MAPI default message store extension that also parses MAPI calendar properties. To develop corresponding MAPI service providers that function as MAPI data stores and sources.

Project Communication

Discussion on the development of this project is at .  Further information can be found at the sourceforge project page at . Additionally the list is archived at Mail-Archive at The Mail-Archive archive is much more reliable, but is quite recent.

How you can help

If you have a few hours per week to work on an interesting project, and you know C++ on the Windows Platform very well, or you are very good at debugging, then you can help us. Understanding of MAPI is not an absolute prerequisite; But you must be willing to spend a lot of time reading in that case. We are always ready to answer any questions.

If you can not program, consider Donating to the Open Source Outlook Connector project to help offset the cost of developer time.

Project Status

07JUL08 -

Work on Milestone 4 is ongoing, with support for Delegates a top priority. We have a new development blog at Visit the blog for information on testing the connector, source code issues, development status, etc. Also a new website is also in the works. We are hoping to have both Milestone 4 and the new website ready by Aug 31st.

12DEC07 -

New Snapshot is available. Milestone 2 of the coming 0.5 release is available for download from . Also a new Demo Video is available. Make sure you do not install this snapshot on a production system and please watch the demonstration video for install and configuration instructions. This snapshot introduces Outlook 2007 support and support for the latest Bedework and Apple Calendar servers, amongst numerous other improvements and bug fixes. There is still a lot to do though.

31JUN07 -

Bedework, the open-source, enterprise calendar system for higher education, will be working closely with the Open Connector Project, developers of open-source extensions for Microsoft Outlook®, to better support CalDAV in Outlook 2003 and Outlook 2007. Bedework will be providing funding to the Open Connector Project, and will participate in testing the open Connector CalDAV support using Outlook in an Exchange environment as well as a standalone calendar client. More...



11JUN07 -

We are working towards a stable release! If you have experience programming MAPI Service Providers or can help the project in anyway, please contact us.


22OCT06 -

New snapshot installer available at . Also new Demo Videos are available.


12JUN06 -

New snapshot installer available at . This snapshot should be stable enough to test individual calendars against most CalDAV servers. We need testers! Please let us know about your experience on the mailing list.


23MAR06 -

Very big thanks to Geir Isene of Freecode and the FRESCO organization for sponsoring Open Connector development. Freecode and FRESCO are providing the funds to get the our Outlook connector to a stable first release. More information on Freecode and FRESCO will be released soon.


01MAR06 -

Thanks to IconTree for donating free icons to the project.


13FEB06 -

Thanks to AutomatedQA for donating a license to their performance profiler and memory allocation debugger. As we are getting closer to public releases the importance of performance optimization is increasing. AQTime should help us meet our performance goals.


07FEB06 -

Work Continues on getting to the Beta milestone by May 1st. A new developer snapshot is available from the sourceforge project page. Note that this is a developer's preview, you will have to have Microsoft Visual Studio .NET installed for it to work.

We need a web designer! Do you have experience designing website built on the 'Mambo' or 'Joomla!' Content Management Systems? If yes, send me a message if you would like to help.


22NOV05 -

The message connector loads up in Outlook and appointments can be saved in our calendar folder. There is still a lot to be done but the features needed for a basic message store provider are almost all done. Table sorting and various finishing touches and optimizations are left for the message store, then the transport provider is next.

On a more technical note SQL Schema documentation for the underlying SQLite database has been started but still in the early stages. Also a some amount of documentation is generated for the O_ITable class. Again, just a start.


28JUL05 -

Uploaded a new snapshot of the message store and transport store source code. The latest code can allows be found in CVS source control but I've zipped up a snapshot for those not wanting to go through the trouble of configuring CVS. The code can be found at

I could really use help in debugging the message store. If you have any experience with developing MAPI message stores, then please send us a message. The more volunteers debugging the source code, the faster we'll get done. Microsoft Visual Studio 2003 and Microsoft Outlook 2003 is needed.


03FEB05 - Help is needed developing the BClient Communications Protocol Library. This component requires no MAPI knowledge at all, just regular WinSock Win32 programming. If you would like to help with the protocol library please contact the mailing-list.
The basic message store provider loads now. Help is needed to get this message to be recognized in Outlook as a 'default' message store and to start the development of the transport provider.
We received a donation for the purchase of a copy of "Inside MAPI" from the developers of the DeskNow collaboration and communication software suite. Thanks to DeskNow, we should have an extra loaner copy of "Inside MAPI" for anyone who needs it.
Work continues. Felix Deschamps got his message store backend to load in Outlook. I am working on using Sapimapi testing utility to display MAPI tables sent from Outlook via shared memory. Should have results for that in a bit. We are hoping to receive "Inside MAPI" book donations if anyone is interested. Also, MAPI developers in general are welcomed to join the mailing-list and help out.
Has been a while since an update. Work continues on the testing utility and the otlkcon DLLs, but due to lack of resources ( time, other programmers ), things are moving a little slower than I would like. If you are an experienced Win32 C/C++ developer with a few hours to spare now and then, then now is a good time lend a hand.
Work continues on the MAPI test program. I'll switch focus back to the message store DLL as soon as I can parse a few simple test scripts.
Message store just past 'skeletal' phase registered in MAPI profile and loads but fails soon after. It is fustrating to debug in outlook, so I started a looking into a 'MAPI test environment'.

Sapimapi is an effort to produce an open-source scriptable MAPI testing/debug environment. I hope to produce something like 'OutlookSpy', but allows MAPI internals investigation through a scripting language.

Work continuing on default message store.

Planning, configuring sourceforge tools, test environment.



  1. CalDAV - In progress Calendar sharing/scheduling protocol.
  2. Bedework - An open source CalDAV server.

for more information contact Kervin Pierre

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