PST to MBOX is the perfect software to export PST files to MBOX format. PST to MBOX Converter supports all popular versions of MS Outlook 2019, 2016, 2013, 2010, 2007, 2003 etc. This software supports more than 20 MBOX based email clients such as Apple Mail and Pocomail. Eudora, Spicebird, Entourage, Google Takeout, Netscape, SeaMonkey etc. There is no limit to the size of the files as the software can import files of any size without errors. Software support in ANSI and UNICODE formats.
I have used many manual methods but did not satisfied with any of the methods. Being a non-technical user, I first go through manual methods but due to some issues, I found it not effective so I used PST to MBOX Converter and got best results. You may go for the tool. Refer:- https://www.osttopstapp.com/pst-converter.html