Imap mail accounts synchronise with server to show what is on server. Emails are stored on server. Even if you download full copies, you cannot regard them as stored on your computer because the folders synchronise with server and only show what is on server. eg: If you accessed webmail and deleted an email, then when Thunderbird imap account accesses server, that email would get auto deleted from Thunderbird because it is not on server. If you want to be able to keep emails and read them should that email address no longer exist or if server becomes inaccessible then I suggest you download full copies and get them copied into suitably named folders in your 'Local Folders' mail account. Make sure the Imap account is set up to download full copies to all folders. * Right click on imap mail account name in Folder Pane and select 'Settings' * Select 'Synchronisation & Storage' * select 'keep messages for this account on this computer' * click on 'Advanced' button * make sure all checkboxes for all folders including subfolders are selected to get a download. * click on 'OK' * click on 'OK' * Menu icon > File > Offline > 'download/sync now' * Select download 'Mail Messages' * select any other checkboxes required. * Select: 'Work offline once download and/or synchronisation is complete' * click on 'OK' Once everything is synchronised and downloaded, Thunderbird should then go into 'Offline' mode. It is a good idea to work in offline mode if you are copying a load of emails from various folders as it prevents those folders from synchronsing whilst you are performing alot of moves/copies. * Create new folders in 'Local Folders' mail account. * Select/highlight emails * right click on emails and select 'Copy to' and choose the appropriate folder in 'Local folders' mail account. * Repeat until all emails are copied from server. If you can read emails in offline mode and in Local Folders mail account then you know you have got good copies stored on your computer in an account that cannot synchronise with server. Then you can go back to online mode by clicking on the 'two black screen icon' located bottom left of Status bar. The icon will then change to a 'two blue screen icon' to show you are in online mode.