Shoviv Imap Backup and Restore tool allow users to backup emails from IMAP servers into several email file formats such as PST, MBOX, EML, MSG, and many more. Alternately, you could consider using. Alternatively, you can try the Thunderbird PST Import plug-in. This plug-in is open source and claims to help your Thunderbird client recognize and import .pst files. It's unclear how it functions, and many of the comments on the download site say that the plug-in is not clear what to do and doesn't function as advertised.
Always make backups of your data before trying every Thunderbird export .pst method. When you import files, you are constantly faced with the risk that the files could become damaged or unreadable on the machine.
imap ranks #722 in the community leaderboard with total of 0 reputation points.