I would suggest using the smart KDETools PST to MBOX Converter tool available on the market, which allows users to export and save data in various file formats like PST, MSG, EML, PDF, HTML. All users, technical and non-technical, can easily use this robust software. The user can get a free preview of the content before the conversion process begins.
READ MORE: https://www.kdetools.com/pst/mbox/
If you want to convert your Outlook PST file to MBOX file format with ease. You can go with this PST repair tool which can save PST files in multiple formats like MBOX, DBX, EML, PDF, MSG, RTF and HTML. The user can also migrate repaired PST file data directly to Office 365 mailboxes. The tool supports Windows 10, 8.1, 8, 7, Vista, XP, 2000 and 98 operating systems. To learn more about the tool, visit: https://www.datarepairtools.com/outlook-pst-repair.html