Overview of PST File An Outlook PST file is a Personal Folder File which is responsible for storing the email messages and items such as journals, notes, tasks, calendars, contacts and other attachments on your system. It is the preferred file format used by MS Outlook. Any email message that you send or receive using MS Outlook is stored on your PC in the form of an. • • Causes for PST Files corruption are: PST files are prone to errors and corruption just like Excel and Word files.