1. Boot into Windows.
2. Download Thunderbird for Windows and install it in Windows. During installation, Thunderbird will offer to import all emails, contacts and settings from Outlook/Outlook Express. Agree to that. Wait until the data import has finished. (Could be a long wait!)
3. Now you need to copy the Thunderbird profile folder (containing the e-mails, contacts and settings that you've imported) onto a USB memory stick.
You can find that profile folder from within Thunderbird by single left-clicking the Menu button (the button with three horizontal lines on in the top right hand corner), then hovering over Help then single left-clicking Troubleshooting Information.
In the Application Data section you will see a button marked "Open Folder" - single left-click that button to open the user profile folder.
Then move one level back in the location bar so that you can select the whole of the user profile folder (its name is an arbitrary combination of letters and digits, but always ends with .default. For example: brfnan5s.default)
Let's call it: fullprofilefolder.default
4. Keep the profile folder window open but close Thunderbird. Copy the profile folder onto the USB memory stick, shut down Windows and boot the Linux computer (or partition).
5. Ensure that Linux is completely up to date with all updates. This will minimize the differences between the Thunderbird version in Windows and the Thunderbird version in Linux.
6. Launch Thunderbird in Linux. Click the option to configure your account later.
Then close Thunderbird.
7. Open the home folder with the file manager.
Use the shortcut (key combination) Ctrl h to make the hidden files visible (unhide them).
8. Open the hidden settings folder called .thunderbird (with a dot before the name, that makes it hidden). In that folder you find the current (nearly empty) profile folder of Thunderbird in Linux.
The name of that profile folder is again an arbitrary combination of letters and digits, but always ends with .default. For example: brfnan5s.default
For the purpose of this how-to I'll call it emptyprofilefolder.default
Now delete the current profile folder emptyprofilefolder.default. And put the new profile folder fullprofilefolder.default that's on the USB memory stick, in that location instead.
9. Almost done, but not quite: now double-click on the file called profiles.ini in the folder .thunderbird. That causes that text file to be opened in a text editor.
In the last line of that text file, you see a reference to the name of the former profile folder. In this example: Path=emptyprofilefolder.default
Change the old name into the new name:
Take care not to make mistakes when typing the name, even though it's a complex combination of letters and digits. Because it has to be exactly right!
Save the modified text file and close it.
11. Launch Thunderbird in Linux Mint: it should now contain all of your e-mails, contacts and settings.