If you need to convert PST files to Thunderbird, I'll show you how to utilize eSoftTools PST to MBOX File Converter Software, one of the best programs available. There are a few factors to keep in mind when converting PST files to MBOX files. This program has a split option that allows you to split PST files into different sizes. The demo version is available to all users.
TrustVare PST to MBOX Converter Tool is the reliable software to migrate Outlook PST into Mozilla Thunderbird MBOX. It switch the complete information of the PST data into MHTML, HTML, EML, MSG, IMAP, MBOX, TGZ and EMLX, Gmail, Yahoo, G Suite account, etc. An advanced utility to give complete explanation convert PST file to MBOX. It even useful to move PST emails and attachments separately into MBOX file format. The app performs conversion without altering/missing PST data.