If you are talking about an IMAP mail account: * Right click on 'Imap mail account name in Folder Pane and select 'Subscribe'. * Select the name of the server 'Sent' folder which may be called something similar like 'Sent Items' or 'Sent Mail'. * click on 'Subscribe' * click on 'OK' Now check to see if your imap mail account is set up to use that server sent folder. * Right click on 'Imap mail account name in Folder Pane and select 'Settings'. * Select 'Copies & Folders' for the account. * select 'Place a copy in' : * Select 'Other' and choose the server Sent/Sent Items folder for that account. * click on 'OK Restart Thunderbird.