What is a PST File
A PST file (Personal Storage Table) is a filename extension associated with Personal Folders files used with certain Microsoft products. Personal Folders (.pst) files are used to store local copies of messages, calendar events, and other items within Microsoft Microsoft Exchange Client, Windows Messaging, Microsoft Outlook, and Microsoft Outlook Express.
Versions of a PST file
Outlook 97
Starting with Microsoft Outlook 97 the Personal Storage file is encoded in ANSI format. It has a maximum file size of 2 GB. If the file exceeds this size it will become corrupted. This format is supported by Microsoft Outlook 97, Outlook 98, Outlook 2000, Outlook 2002, and Outlook 2003 Internet Message Access Protocol Version 4rev1 (IMAP4) accounts and HTTP accounts.
Outlook 2003
Starting with Outlook 2003 the Personal Storage file is encoded in unicode format. It allows a user-definable maximum file size up to 33TB that exceeds the previous limit of 2GB. This format is supported by Microsoft Outlook 2003 and Outlook 2007.