If you use POP mail accounts and in 'Account Settings' > 'Server Settings' selected the option to 'Leave messages on server', then a copy of all emails should be on the server. POP mail accounts can only access the server Inbox and download emails. So the emails in Thunderbird are independent of the server. check that emails are on server first by logging into the webmail account using a browser. If you remove the mail accounts via Account Settings, then the mail accounts will disappear from the Thunderbird Folder Pane, but will still have those emails in your Profile folder - designed to be able to recover a mail account deleted in error. You would still need to access and manually remove the mail account folder located in the 'Mail' folder. Thunderbird must be closed before doing anything in the Profile folder. This link will tell you the location of your Profile folder. * http://kb.mozillazine.org/Profile_folder_-_Thunderbird you would need to make hidden files and folders visible to see them. * http://kb.mozillazine.org/Show_hidden_files_and_folders then you can delete and sort emails on the server via webmail. when all is ok, create a new pop mail account to download everything on server. Please note that gmail pop mail accounts record what has been downloaded and you can select to get a fresh download, but it might only let you get the last 30 days worth. However, as you use two different computers to access one mail account/email address, then you might like to consider IMAP. IMAP mail accounts see a remote view of the folders on the server. If you already use IMAP, then any emails you delete in Thunderbird will get deleted off the server as the folders are in effect one and the same.