Archiving the data from you mailbox is a practice regulated by your company
policy. Normally you should do it at least once a year. This process reduces the
size of your mailbox on the Exchange server while you still have access to it in
your Outlook in your Archive folders. here is demonstrated how to perform the
Archiving and create the PST file - Step1 and the opposite process - importing
the archived data from your PST file, Step2.