You can use an excellent tool to convert Outlook PST to Thunderbird converter for free download. Using the eSofTools PST to MBOX Converter Software. It can easily convert all the outlook PST to MBOX Files. That work is very simple and quick. This software is a good option for converting PST to Thunderbird and the trial version is available for all buyers.
Read more:- https://www.esofttools.com/pst-to-mbox-converter.html