Best Way to change PST File to MBOX!!!
To change a PST file to MBOX, a manual method involves using Outlook to export PST data to EML format and then dragging the EML files into an MBOX-supported email client like Thunderbird. While feasible, this process is time-consuming and prone to errors, especially with large files. A more efficient solution is using the BLR PST Converter Software, which seamlessly converts PST files to MBOX format, preserving data integrity and folder hierarchy. This tool ensures a quick and hassle-free experience.

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Carlie levins commented
The selective conversion option is a great feature of the Enstella MBOX Converter software. My own experience with it was great, and I converted only the folders I needed.
Read More - https://www.enstella.com/mbox-converter.html