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