For merging multiple Outlook PST files into one, consider using the Advik PST Merge Tool. It's safe and secure, ensuring no duplicates in the merged PST file. Unlike the manual method, where you have to select PST files one by one, this tool lets you merge several PST files at once. It's lightweight and has some unique features. This freeware efficiently combines multiple Outlook PST files into a single file. It's compatible with Microsoft Outlook versions 2021, 2019, 2016, 2013, 2010, 2003, and 2000.