If you want to convert PST to MBOX Thunderbird, you should use eSoftTools PST to MBOX Converter, which is the best solution available. To convert a pst file, there are only a few more steps to take. For conversion, both ANSI and UNICODE PST files are acceptable. Both new and old versions of Microsoft Outlook are supported by the application. All users have access to the trial version, which allows them to convert up to 25 email items per folder for no charge.
Read more:- https://www.esofttools.com/pst-to-mbox-converter.html