From Microsoft:

This spring, Microsoft released technical documentation for the .pst file format used to store data in Microsoft Outlook Personal Folders, such as email, contacts, calendar events and attachments.  Today, Microsoft announced two new open-source projects that give developers access to .pst files even when Microsoft Outlook is not installed on the desktop.  These include a.pst Data Structure View Tool and a .pst File Format Software Development Kit (SDK) that makes it easier to read and extract data for use in new applications across a range of platforms. 

These new tools open opportunities for competitors, customers and partners to build new solutions that interoperate with the data in .pst files and use it for solutions that include uploading to the cloud or complying with corporate governance policies.

And the press release:

Microsoft Delivers on Interoperability Principles With Office Outlook

New open source technologies facilitate interoperability with popular Outlook data files.

REDMOND, Wash. — May 24, 2010 — Microsoft Corp. today announced the availability of two new open source projects that complement technical documentation recently released for Microsoft Outlook Personal Folders (.pst). Combined, the documentation and tools advance interoperability with data stored in .pst files, reflecting customer requests for greater access to data stored and shared in digital formats generated by Microsoft Outlook and for enhanced data portability.

Developers can use these resources to more easily build solutions, including competitive products, that run on top of the .pst file format, unlocking data stored in .pst files in simple scenarios, such as extracting photos stored in .pst files to create an album, as well as more complex scenarios, including archive search, e-discovery and corporate compliance, and uploading data to the cloud.

The technical documentation, released in line with the company’s Interoperability Principles, makes it easier for developers to read and write data out of .pst files on any platform, regardless of whether Microsoft Outlook is installed. Developers previously could access the data stored in .pst file format using Messaging Application Programming Interface and the Outlook Object Model — a rich set of connections to data stored by Outlook and Exchange Server, available when Outlook is installed on the desktop.

Now, two new open source projects, a .pst Data Structure View Tool and a .pst File Format Software Development Kit (SDK), further reduce the complexity of reading and extracting data stored in .pst files for use in new applications across a range of platforms. 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.

“Our customers have expressed a strong interest in search solutions that offer access to .pst archives. The formal .pst specification documentation that Microsoft released is of the highest quality and makes building solutions that leverage the .pst format practical,” said Dave Vest, director, MythicSoft Ltd. “This documentation allowed us to rapidly integrate .pst archive searching into our flagship product within two weeks.”

Data portability is increasingly important for customers operating complex, heterogeneous technology environments. Research commissioned with IDC reflects that in 2009, the amount of digital information created and replicated grew by 62 percent.1

“The industry as a whole benefits from tools and information that enhance interoperability with our most popular products. The .pst documentation makes it easier for products from other vendors to interoperate with Outlook data,” said William Kennedy, corporate vice president, Office Communications and Forms at Microsoft. “Customers are telling us they need greater interoperability, and we believe that welcoming competition and choice will create more opportunities for customers, partners and developers.”

The .pst file format documentation reflects feedback from a community of reviewers and is now available at http://msdn.microsoft.com/en-us/library/ff385210.aspx. It follows the publication of thousands of pages of protocols provided since the release of the 2007 Microsoft Office Suite Service Pack 2 and the publication of the Outlook Personal Folders File Format (.pst) Structure Specification under the Microsoft Open Specification Promise. Increasing access to information and transparency is central to the Microsoft Interoperability Principles announced in 2008. More information about the .pst File Format SDK and .pst Data Structure View is available on the Interoperability @ Microsoft blog.