Hello, I have had to re-install Thunderbird after a disastrous upgrade to a more recent macOS, and subsequent downgrade. I thought that all my information would be preserved in the various Time Machine backups that I have made. However, all of my local folders containing 18 years' of email correspondece have disappeared. I can only view emails which are stored on the remote IMAP server. Any assistance would be greatly appreciated. Kind regards, John.