Watch this online video tutorial and learn the best way to reduce Outlook mailbox size using Compact Now feature of Outlook. It removes the deletes item's space from Microsoft Outlook 2016, 2013, and 2010 and compresses the PST file size. This will help you to boost Outlook performance. But, sometimes Compact PST does not reduce the size or not work due to large PST or some other reasons. In that case, you have to use a third-party application (i,e: SysTools PST compress tool
) to compact Outlook PST file without any limitations.