Is the account in Thunderbird IMAP or POP? Is the account in Outlook IMAP or POP? Is the account in Andriod IMAP or POP? If you log on to the webmail account via a browser - do you see the email - is it still on server? Please post image of webmail view. Do you have these settings: View > Folders > All View > Threads > All Have you tried selecting : View > Threads > Ignored threads to see if by any chance you accidentally set as ignored ? Do you have any filters working in Thunderbird on the account? If yes, have you checked the filter log to see if that email was moved? Do you have any 'Quick Filter Bar' icons selected/highlighted which may be causing a filter on the folder ? If you search for email, does it pop up in the search results?