So, to export files from Outlook’s .pst format to Thunderbird on the Mac, you can
- Buy a copy of emailchemy
- Run emailchemy on the .pst file
- Extract the resulting file from the folder hierarchy created by emailchemy
- Quit Thunderbird if you haven’t already
- Copy the file generated by emailchemy (it’s just a text file containing multiple e-mail messages) into /Users/yourusername/Library/Thunderbird/Profiles/blah.default/Mail/Local folders/