You can export Thunderbird to EML files by using the professional tool Softaken Thunderbird to EML Converter. It has various features that help to convert multiple mbox-supported email client mails to the EML file format with attachments. It GUI is too easy and simple, so any kind of user can operate, whether they are skilled or not. It provides free demo versions to all to convert a few Thunderbird mbox files to EML for free.