How to Import an MBOX using Thunderbird
A MBOX file is one file containing many email messages in a row.
Mail-List.com can Import or Export your Searchable Web Archive from or to the MBOX format.
Thunderbird is a free open source email reader
For the Windows, Macintosh and Linux Operating Systems.
Many people consider Thunderbird the best email reader available. It has a lot of features and optional functions that can be added.
Thunderbird needs the ImportExportTools Add-on
ImportExportTools will add a new menu item allowing you to import (or export) an mbox.
So the trick is to get the Add-on installed and Thunderbird Restarted, then you can import the mbox file.
Copy the above URL to your web browser address bar
Unfortunately, ImportExportTools is not one of the built in Add-ons that you can install from within Thunderbird.
Save the Download to your computer - will end in XPI
Install the downloaded Add-on
Open the Tools menu, and choose Add-ons
A new tab will open.
Click on Extensions menu on left hand side, and open the Setting (Gear) drop down
Click on - Install Add-on From File ...
Navigate to your Download folder and find the file
and click on the Open button
Acknowledge the - Install add-ons only from authors you trust
Click on the Install Now button
Click on the Restart Now link
Thunderbird shuts down and opens back up with a new menu item
At the very bottom of the Tools menu, is ImportExportTools
Get into a Thunderbird email account, such as Local Folders
Click on Tools -> ImportExportTools -> Import mbox file
Radio Button = Import directly from one or more mbox files
Navigate to the location of your mbox file
Select the file and click Open