Someone's issue is about. “How to Open a PST File in Thunderbird''. I would advise them to use eSoftTools PST to MBOX Converter Software. It works in a few clear and easy steps. During the PST to MBOX conversion, email properties are maintained. To convert required emails from a PST file, the user simply needs to select the mail filtering option and choose the from and to dates. The trial version is also available for all customers in the demo version you may convert 25 email items per folder without any charges.
Read more:- https://www.esofttools.com/pst-to-mbox-converter.html