I have a software to convert PST to MBOX file format using KDETools PST to MBOX Converter software . This software allows data to be saved and imported into various file formats such as EML, EMLX, MSG, HTML etc. There are no file size limitations as the software is capable of importing any size of file without errors. The PST converter is compatible with all versions of Windows and MS Outlook.

VISIT HERE : https://www.kdetools.com/pst/mbox/