'Local Folders' mail account is stored in your Thunderbird profile folders. If using Windows OS and you have not moved them from the default then they are usually located here: * C:\Users\<Windows user name>\AppData\Roaming\Thunderbird\Profiles\<Profile name>\ Mail\Local Folders You can also check out the directory by looking in the Account Settings. * Right click on 'Local Folders' mail account in the Folder Pane and select 'Settings'. * A new 'Account Settings' window will open. * On the right side look for 'Local directory'. It will tell you exactly where they are located. You can easily access your profile name folder: In Thunderbird * Help > Troubleshooting Information * clickon 'Open Folder' button A new window opens showing the contents of your 'profile name' folder. * click on 'Mail' folder * click on 'Local Folders' folder * Exit Thunderbird now - this is important. You could copy everything by coping the 'Local Folders' folder. Then paste it on any external drive you choose. In the 'Local Folders' folder you will see mbox files; they do not have any extension and will have the same name as the folders you see in the Folder Pane. mbox files contain emails. Any file with a .msf extension is just an indexing file used by thunderbird. It does not contain emails. If you see folders with a .sbd extension then this means that folder has subfolders. A .sbd folder may contain mbox files. You can copy any mbox file and store in another suitable location. '''Alternative options:''' You can save individual emails by right click on highlighted emails and use 'Save as' Choose location and save emails as .eml files. Each email is stored as a separate file. You can use an addon called 'ImportExportTools' This addon would allow you to export the mbox file to wherever you choose. * https://addons.thunderbird.net/en-US/thunderbird/addon/importexporttools/