Microsoft has decided to publish a copy of the Outlook Personal Folder File format (.PST file). You can view the specification at: http://msdn.microsoft.com/en-us/library/ff385210.aspx
The Outlook PST (Personal Folder) File Format Now Available From Microsoft by Forensic Computing, unless otherwise expressly stated, is licensed under a Creative Commons Attribution-Noncommercial 3.0 United States License.