Import or Transfer MBOX files to Yahoo! using MBOX to Yahoo Migrator. The tool supports Mac OS Machines.
Start MBOX to Yahoo Converter on your Mac Computer.
Select MBOX file using Add File(s) or Add Folder(s).
Choose the desired files from the software panel.
Click on the Yahoo in Select Saving Option and then enter Yahoo Email address and Password and IMAP Port and IMAP Host.
Then, press Export button to migrate MBOX to Yahoo account.