Successfully converting an MBOX files into PST needs a advance software solution like Shoviv MBOX file Converter tool. this tool not only export MBOX files but also allow to export MBOX files into Office 365 and Live Exchange server as well as outlook profile directly. This tool contains advanced features like Splitting PST file, Filter option, and incremental expert option.
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Read more: https://www.shoviv.com/how-to/export-mbox-to-pst-manually.php