If you have imap mail accounts: Unsubscribe from seeing folders. So they are removed from view. Then Exit Thunderbird. Before making a backup of 'profile name' folder, exit Thunderbird. All messages are in the mail accounts. In your 'profile name' folder: The 'Mail' folder contains pop mail accounts and 'Local Folders' mail account' folders. Within each mail account folder: * All downloaded/saved messages will be in mbox files. * mbox files have no extension and contain emails. * mbox files have the same name as the folder you see in the Folder Pane. * All *.msf files of same name are indexing files. * If you see *.sbd folders, they indicate you have subfolders and they contain more mbox and .msf files. see image below with examples. * To keep folders but not emails, you would need to create a copy of your 'profile name' folder to alter. Just in case you make a mistake :) * open a mbox file using a text editor like Notepad++ * delete all contents and save file. * Then delete the .msf file of same name. * repeat for each mbox file. If you see *.mozmsg folders, then they contain emails. These folders are created so the you can search using the Windows search. You can delete those folders as they are not the folders you see in Folder pane. note: each pop mail account will also have a 'popstate.dat' file. This file keeps a record of what has been downloaded. If you delete this file, Thunderbird has no record of what has been downloaded and therefore will auto download whatever is in the server Inbox. Do not delete if you do not want to redownload everything from server Inbox. The 'ImapMail' folder contains all your imap mail accounts. As all folders and emails are stored on server, it is just as easy to unsubscribe from seeing imap folders. If there are any mbox or .msf files, you can remove them as all folders and emails are stored on server and it is just as easy to subscribe to see them again. In the 'profile name' folder: * global-messages-db.sqlite This is the global search database file, I suggest you delete the 'global-messages-db.sqlite' file as it will contain all indexing to all those deleted emails.