I would like to suggest the best third party
KDETools PST to MBOX Converter software It can convert various file formats like PST, MSG, EML, EMLX, HTML, etc. It allows batch conversion of PST to MBOX format at one time for exporting email, contacts, calendar, tasks, etc. The PST to MBOX converter is compatible with all the latest versions of Microsoft Outlook like 2019, 2016, 2013, 2010, 2007, 2003 etc.
VISIT HERE: http://www.howtosol.com/products/pst-to-mbox-converter.html
