There are many individuals worldwide who save their contacts on the respective email client they are using for email communication. Some people use Mozilla Thunderbird and all the contacts are saved in an MBOX file if you are using this email client. But when you want to import those contacts on your local mac device then the problem arises. First, you will have to convert MBOX to CSV on Mac, and then only you can import the contacts to your respective mac device.

read more:- https://www.macsonik.com/blog/save-thunderbird-mbox-contacts-to-csv/