The move may mean Outlook works on many different devices.
Microsoft has announced plans to open up the format of the data files used by its e-mail program Outlook.
The software giant said it would provide full documentation on the format so non-Microsoft developers can interrogate and use it.
Microsoft said it was making the move because data portability was becoming increasingly important to customers and clients.
No deadline was given for when the documentation effort will be complete.
Microsoft already provides two ways to get at the data Outlook and Exchange servers store about e-mail messages, contacts and calendar entries in a format known as .pst. However, that information can only be accessed if Outlook is installed on a user's desktop or laptop computer.
The documentation effort will provide full information about the .pst file format and remove the need to have Outlook installed to get at it.
"This documentation is still in its early stages and work is ongoing," wrote Paul Lorimer, group manager, Microsoft Office Interoperability, in a blog post announcing the move.
When the documents are complete, Microsoft said they would be released to make it possible for anyone to use the .pst format "on any platform and in any tool, without concerns about patents, and without the need to contact Microsoft in any way".
Microsoft said it was already talking to key customers and industry experts to ensure the information it provides is useful.
The move could see novel e-mail, contact and calendar clients that work on many different devices.
Mr Lorimer said the move was taken as part of Microsoft's commitment to Interoperability Principles that it announced in 2008.
Microsoft is not alone in pursuing a more open agenda for its products. Many firms now provide detailed interfaces to their data or software so others can find out how they work and put that information to their own ends.
For instance, in September Google set up a Data Liberation Front - a team of engineers whose job it is to ensure that its users can get at their data and do what they want with it.