Sounds like your imap account in Thunderbird may look empty but it has a record of deleted emails which upon exit has Inbox expunged - compacted so all traces of deleted emails are removed - hence they then disappear from OWA. Removing and reinstalling Thunderbird will have no effect as nothing is wrong with the actual program. It's more likely something has gone wrong with the profile folders which contain the mail account. I would try this: Start Thunderbird in '''Offline mode''' using the following info: In Windows search type: '''Run''' select '''Run''' app Enter this: '''thunderbird.exe -offline''' Click on 'OK' Thunderbird should start up in 'Offline' mode meaning it has no access to internet. Make a note of the server settings and the stored password as you will need it. Remove the imap account via: * Account Settings * Select name of account in left pane * click on 'Account Actions' * select 'Remove account' Check all passwords relating to that account are gone. * Settings > Privacy & Security * Passwords section * click on 'Saved Passwords' * click on 'Show Passwords' * If you see any lines that have username = email address of removed account - select them and click on 'Remove', so there is no record of saved passwords. Exit Thunderbird. Check all emails are recovered into the Inbox in webmail account Start Thunderbird normally. create new imap account for the email address. check all the Account Settings etc are as required.