Outlook data files can get very large over time, especially if you get a lot of attachments. Even if you delete old messages, the size of your Outlook data file is not reduced accordingly. Your Outlook data files ( .pst and .ost files ) include all your emails (in all your folders, including sent emails), contacts, calendar appointments, tasks, and notes, as well as their associated file attachments. As you send and receive more emails and attachments, add more appointments to your calendar, and create more tasks and notes, your Outlook data files can easily grow to several gigabytes in size. Mine is one gigabyte, but that’s still pretty large. RELATED: How to Automatically Empty the Deleted Items Folder When Exiting Outlook Even if you empty the Deleted Items folder, or have it automatically emptied when you exit Outlook , the space occupied in the data file is not released. You can, however, reclaim that space by compacting your Outlook data file. Here’s … [Read more...] about How to Reduce the Size of Your Outlook Data File