If you want to combine multiple PST files without losing their original folder structure, I recommend using the DataVare Outlook PST Merge Expert Tool. It is specifically developed to securely merge or join multiple Outlook PST files while retaining all email attributes, attachments and folder hierarchy.

Here how to do it step by step

• Download and install the DataVare Outlook PST Merge Expert Tool into your computer.
• Launch the software and select Merge PST to combine data into a single PST or Join PST to add PST as subfolders.
• Add your PST files you can add multiple files at once by clicking the Add File or Add Folder button
• Choose a merge mode such as contacts, calendars, emails etc.
• Choose a location to save the combined PST file
• Click Merge Now and start the procedure

Key Advantages

• Maintains the original folder hierarchy perfectly
• Supports both ANSI and Unicode PST files
• Compatible with all versions of Microsoft Outlook (Outlook 2021, 2019, 2016, 2013, etc.)
• No Outlook installation is required for merging
• Maintains data integrity no duplicates loss or corruption

It is more dependable than manual techniques or importing/exporting using Outlook. This saves time while managing multiple versions or mailbox PST.