You can easily convert Mac OST files using MacUncle OST to Thunderbird Converter. The tool supports Mac OS Machines.
Start MacUncle OST to Thunderbird Converter on your Mac Computer.
Select OST file using Add File(s) or Add Folder(s).
Choose saving option as Thunderbird.
You can also select the File Naming Option and Choose Destination path if required.
Mac OST to Thunderbird conversion process completed successfully, you can see the message of completion.