Enter your email address: Delivered by A Personal Folders file (.pst) is an Outlook data file that in general stores the messages and other items on your computer. In fact, this is the most common file in which information in MS Outlook is saved by home users or in small organizations. The key point to note is that as a.pst file is kept on your computer, it is not subject to mailbox size limits on the mail server. Therefore, by performing a simple act of removing items to a.pst file, it gets easier for you to free up the storage space in the mailbox. But just like any other file format, these.pst files also get corrupt in various circumstances. There are all sorts of reasons why an Outlook PST file can become corrupt, and whenever such unwanted incidents happen; it stops working. If you work within any size business that depends upon MS Outlook, chances are you will need the services of a PST repair tool.