Please let us know if there is a way to import PST files from Outlook to Thunderbird without using Outlook. The eSoftTools PST to MBOX Converter Software helps to convert PST to Thunderbird without needing to worry about Outlook migration issues. There are just a few more steps to complete. The tool can be exported PST files as separate MBOX files. The free trial version can export 25 emails from each folder of the PST Outlook file.