Microsoft is to provide patent- and licence-free use rights to the format behind its Outlook Personal Folders, opening email, calendar, contacts and other information to a host of applications such as antimalware or cloud-based services.

Documenting and publishing the .pst format could open up entirely new feature sets for programs such as search tools for mining mailboxes for relevant corporate data or new security tools that scan .pst data for malicious software, according to Microsoft officials.

The written documentation would explain how to parse the contents of the .pst file, which houses the email, calendar and contact contents of Outlook Personal Folders. The documentation will detail how the data is stored, along with guidance for accessing that data from other software applications. The effort is designed to give programs the knowledge to read Outlook data stored on desktops.

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"You could also imagine this being used for data portability possibly into the cloud," said Paul Lorimer, group manager for Microsoft Office interoperability. "A user might have data on a hard drive that they would like to migrate to a cloud service. This would allow the cloud service developers to write code on the server so someone could upload their .pst and have it read on the server rather than needing Outlook to be running on the client and somehow get the data that way."

Microsoft plans to publish in the first half of next year documentation outlining the .pst format. The information will be released under Microsoft's Open Specification Promise (OSP), which began in 2006. That year, Microsoft dropped intellectual-property and patent claims to 35 web services protocols it developed mostly for use in its identity infrastructure.

Once the documentation of the .pst format is public, programmers can get into .pst files and read the contents without the need for Outlook. In fact, there will be no requirement for any Microsoft software. Users are free to choose any platform, including Linux and any development language, such as Java or Ruby on Rails.

Data in the .pst file is available to developers today via Microsoft's Messaging API (MAPI) and the Outlook Object Model, but Outlook needs to be installed on the desktop.