Outlook .pst file format and interoperability

This week, the Outlook product team hosted a .pst file format interoperability event here on the Microsoft campus in Redmond. As we announced on the Interoperability @ Microsoft blog, our team plans to release a specification of the .pst file format to the public. This week’s interoperability event is part of a series of steps that we are taking to gather feedback from industry partners and experts on preliminary drafts of the specification. If you are not familiar with the underpinnings of Outlook, .pst files are one type of data file that Outlook uses to save user data such as e-mail messages, contacts, and appointments.

During the interoperability event, we presented a preliminary specification of the .pst file format to selected industry experts in areas such as antimalware, electronic records management, data archiving, data recovery, and data migration. We collected useful feedback about our documentation roadmap, and the attendees were supportive of the direction and approach we are taking.

We understand our plan to document the .pst file format might cause some of our customers and partners to wonder about our commitment to MAPI (Messaging API) and the Outlook Object Model as interoperability mechanisms of Outlook. To us, the .pst file format specification doesn’t change the role of MAPI and the Outlook Object Model. While we are pleased to provide another mechanism to access data stored in .pst files, we continue to support MAPI and the Outlook Object Model as key elements of Outlook interoperability and extensibility. We do expect that the release of the .pst file format specification will open up new usage scenarios that were previously difficult to accomplish, especially in multi-platform and server scenarios where MAPI and the Outlook Object Model are not available.

Since we announced our plan to release the .pst file specification, we have received requests from people who want to participate in the review of early drafts of the specification. If you are interested in actively participating in the review of preliminary drafts of the .pst file format specification, send an email message to pstinfo@microsoft.com and then we will contact you when a preliminary draft of the specification is ready for broader review. If you only are seeking the final version, we anticipate releasing the .pst file format specification in the first half of 2010 under our Open Specification Promise.

Daniel Ko
Outlook Development Manager