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