MS- Outlook, by default, stores all your maiL calendar items, contacts and other informa*tion in a native PST file. If this file were to go corrupt or get deleted, you would lose all of your correspondence. tasks, appointments and contact information.
Hence, backing up this file is a very important part of any system maintenance routine. Personal Folders Backup is an add-in that backs up PST files at reg*ular intervals automatically without manual intervention.