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Microsoft to open up Outlook's .pst format

By Barry Collins

Posted on 27 Oct 2009 at 07:35

Microsoft is planning to open up the .pst format, allowing third-party developers to create applications and services based on Outlook data.

The development will give other software access to data such as email, calendar and contacts entries, potentially making it more accessible to mobile or cloud-computing services.

Developers can currently access data stored in the .pst file, but only if Outlook is installed on the desktop client. Microsoft's proposals will allow that data to be accessed "on any platform and in any tool, without concerns about patents, and without the need to contact Microsoft in any way".

The company plans to release the technical documentation for the .pst file as part of the Open Specification Promise it announced back in 2008, although Microsoft hasn't said when the information will be released.

"This documentation is still in its early stages and work is ongoing," Paul Lorimer, group manager for Microsoft Office interoperability writes on the company's Interoperability blog.

"We are engaging directly with industry experts and interested customers to gather feedback on the quality of the technical documentation to ensure that it is clear and useful."

The move could be good news for Microsoft's rivals, making it easier to port data from Outlook to cloud-computing services such as Google Apps. Last month Google announced its own 'Data Liberation Front', a group of the company's engineers who are dedicated to freeing data from Google services such as Gmail, Docs and and Blogger.

From Microsoft's point of view, the initiative could cement .pst's position as the data format of choice for email/calendaring applications.

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User comments

I suppose you can't really complain about this, it'll mean a lot of email programs will need to be re-written.

By Kid_Spock on 27 Oct 2009

This does sound hopeful but then I remember it's only happening because the EU courts forced Microsoft to play fair; if there'd have been no legal pressure they would have continued being a bully boy. So, although the outward image of the company is improving, it isn't doing so because they wanted it to...

By SwissMac on 27 Oct 2009

"So, although the outward image of the company is improving, it isn't doing so because they wanted it to"
So - damned if they don't, and damned if they do.

By AdrianB on 27 Oct 2009

The pst file should be dead and buried by now. You can't successfully back it up while Outlook is running.

By j9chapman on 28 Oct 2009

What's the big deal

.pst files are the way outlook stores data. If you don't use outlook you don't need them. There are a number of products which can backup, resore and use the data in the files (Dmailer is the one I use).
Surely it would be more useful if outlook supported maildir or mbox storage formats.

By milliganp on 29 Oct 2009

big is the word

what frustrates me and has made me look for a different solution is that to back up a pst file, i have to back up the whole thing. Using a WD worldbook NAS drive, each differential backup was the size of my current pst file.

By fellwalker2000 on 9 Nov 2009

@fellwalker2000 - too true.

Microsoft's post-1994 mantra of "we want to lock people into huge binary formats instead of openable text ones" makes O&M much harder, as for example with your backups. Were they to use a standard text-based format like mbox or similar, your Worldbook backups would positively fly; they'd be truly incremental backups.

By jdickey1 on 30 Dec 2009

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