How can I upload Thunderbird files to Gmail on Mac OS? You can easily complete the process of uploading Thunderbird files to Gmail on Mac by using the latest Mac Thunderbird Converter in quick and easy manner. Software supports to help you to upload Thunderbird profile (Emails, Address Book and Calendar items) to Gmail on Mac OS with no data loss at all, it supports batch file uploading process also. Download the free Thunderbird Converter for Mac toolkit, it supports to upload 20+ files at a time.