Try top professional software KDETools PST to MBOX Converter Software which export PST to MBOX file, This application allows saving data and export into various file formats such as PST, MSG, EML, PDF, HTML, MBOX, and etc. This software provides Message Filtering option helps the users to select PST items between Start date and End date.

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