How do I import PST to MBOX Thunderbird?
Outlook users can convert their PST files to Thunderbird, a fantastic email client, using the eSoftTools PST to MBOX Converter. All Outlook PST files, including versions 2019, 2016, 2013, 2010, 2007, 2003, and older, can be converted to Thunderbird mbox files, and it supports all Outlook PST files, including versions 2019, 2016, 2013, 2010, 2007, 2003, and earlier. The software is simple to use, and it may be used by both technical and non-technical persons. All users have access to technical support 24 hours a day, seven days a week, and the demo version is free.
For more info:- https://www.esofttools.com/pst-to-mbox-converter.html
william joe commented
Import PST to Thunderbird in 5 Easy Steps
Install Outlook PST Converter Tool and run.
Select PST File for Importing.
Extract PST File Email Items.
Choose Thunderbird email clients from Save As options.
Click on the Convert button to Import PST files to Thunderbird.