There are many ways to convert PST to MBOX file format, so you can try KDETools PST to MBOX Converter. PST to MBOX Converter is reliable, safe and professional software for importing PST to MBOX files. Users can save data and import various file formats such as PST in EML, EMLX, MSG, HTML, etc. You updated the feature-selective conversion that converts items and folders from PST to MBOX files.
Download here: http://www.howtosol.com/products/pst-to-mbox-converter.html
PST to MBOX converter software you need for data conversion and data recovery. You can also use this KDETools PST to MBOX Converter software. Converts PST to EML, EMLX, MSG, HTML etc. The software-compatible password-protected PST file can also be converted to MBOX format with just one click. PST to MBOX has another advanced function that maintains the original form of the folder structure even after the conversion process.
Visit here: https://www.kdetools.com/pst/mbox/
You can move PST file into MBOX format with the help of the manual method, but the manual method is not sufficient for a large amount of MBOX files. If you have a large amount of PST and you want to transfer PST files into MBOX format fast and accurate, then you should go with any proficient third-party tool such as:- https://www.tooltoconvert.com/psttombox.html
Download, install & run PST to MBOX converter on Windows. Browse to select the PST file to convert Outlook PST into MBOX format. Then, you can preview the entire PST file data. Click on the 'Export' button and export PST to MBOX file format.