By default, choose ‘Archive items in this folder using the default settings’.Under ‘Mailbox-Your Name’, click ‘Properties’ followed by Auto-Archive tab.Click ‘Enable’ to apply settings to all folders.Under ‘Default’ folder settings for archiving select either 3 or 6 months.The recommended number of days is 7 and 14. Select the box to run Auto-Archive on the requested schedule.Within Outlook, go to Tools->Options->Other Tab->Click Auto-Archive tab.To reduce the Outlook Mailbox size, the user is expected to follow these points: Setting-up Auto Archive in Outlook Mailbox ost file as it can be recreated anytime with a fresh configuration of Exchange Server account in the Outlook application. There is no need to take the backup of the Exchange. Recommended: Free Methods to Repair PST File Different Ways to Reduce Outlook Mailbox Size Manuallyīefore pursuing any of the processes to reduce the mailbox size, it is advised to take a full backup of the Outlook PST file as any loss to data can be recovered which may get hamper while performing any process.