If you have POP mail accounts then emails will already be stored in Thunderbird Profile folder. If IMAP, then make sure you have synchronised the subscribed folders and then go into 'offline' mode to stop further activity until all backup is completed. Bacling up Profile: either do this manually by locating the Profile folder name. right click on 'profile folder name, usually called xxxxxxxx.default (where the x's are letters and numbers) select 'copy' and then paste into another folder which you could call 'TBbackup' and also to an external storage device. Some info: * http://kb.mozillazine.org/Profile_backup * http://kb.mozillazine.org/Profile_folder_-_Thunderbird Or use an addon called Importexporttool. This is a really useful addon. * https://addons.mozilla.org/en-US/thunderbird/addon/importexporttools/ this addon can export the profile or just folders or as individual .eml files and other options. You could just move all those emails into 'Local Folders' account so that they are no longer in a specific mail account. You will still be able to see them in Thunderbird. Once you are certain they are all stored safely in 'Local Folders', you can then remove the unwanted mail account. However, it is always a good idea to have a backup.