make hidden files and folders visible: * http://kb.mozillazine.org/Show_hidden_files_and_folders In Thunderbird * 'Help' > 'Troubleshooting Information' * click on 'Open Folder' button a new window opens showing the contents of your profile name folder. * Close Thunderbird now - this is important. * click on 'Mail' folder * click on pop mail account name * delete this file: '''popstate.dat''' popstate.dat keeps a record of what message has been downloaded. If you delete this file, a new empty one will be auto generated when you next run thunderbird. Thunderbird should connect with server Inbox and download everything. So, it does depend what is in the server Inbox, which you can view via the webmail account using a browser. Start thunderbird.