What’s the Difference Between Outlook’s PST and OST Files? Share October 6, 2020 Dm4r Technology Microsoft Outlook stores your emails, tasks, and appointments as either PST or OST files. These both do the same basic job. However, there are some differences that are important, depending on whether you want to backup, restore, or move your data. Read This Article on How-To Geek › Source : What’s the Difference Between Outlook’s PST and OST Files?