Pst file format: Microsoft offers developers new Outlook tools under Apache open-source license

A .PST Data Structure View Tool and a .PST File Format SDK are available under the Apache open-source license.
“The .pst Data Structure View Tool is a graphical browser of internal data structures for .pst files that enables a developer to better understand .pst file content. The .pst File Format SDK is a cross-platform library that allows developers to read data stored in .pst files and develop applications accessing the data. In the near future, the capability to write data to .pst files will be added to the SDK.”

http://msdn.microsoft.com/en-us/library/ff385210.aspx