You can convert Thunderbird files to MSG files. The Softaken Thunderbird to MSG Converter is all that's needed. The tool can be used on its own to change a lot of Thunderbird files and attachments to MSG. It can also save each MSG file on its own or put them all into one MSG file. The app has a free trial that people can use to get a sense of how it works and what it can do. People who only have to change a small number of emails will really like this choice. It can be used with any version of Windows and Outlook, including Outlook 2003 to 2021.