re : ''Can I go to Appdata/roaming/thunderbird//profiles/bqqu90tc.default and copy the contents of the POP account file and paste it into the IMAP file? '' Do it this way. Exit Thunderbird. It must be closed. Access the profile 'pop mail account' folder. You will see mbox files. eg: Inbox, Sent. * mbox files do not have any extension and contain emails. *.msf files are just indexing files. eg: 'Inbox.msf'. They do not contain emails. *.sbd folders can contain mbox files. Copy the mbox files and paste them into the 'Local Folders' mail account. Start Thunderbird. You should see those folders under 'Local Folders' mail account. This should get you access to see emails. If you really need to put them back onto the server. Note it will reduce your quota. Right click on highlighted email and select 'Copy to' and choose the imap mail account and folder of choice. Imap account should synchronise with server and put email on server. You can confirm this has occurred correctly by logging on to your webmail account.