Hey there! It sounds like you're facing an issue with the recent Thunderbird update that deleted some folders and data within them. I get how frustrating that can be. To restore Thunderbird to its previous state, you can try a couple of things. First, you might want to check your Thunderbird profile folder for any backup copies of your data. If you have backups, you can replace the affected folders with those backups. Alternatively, if you use an email provider that supports IMAP, your emails might still be on the server. You can try re-syncing Thunderbird with the server to retrieve your missing emails. If those options don't work, you might need to manually re-import your emails if you have local backups. Remember, always backup your important data before making any changes. Hope this helps, and good luck getting your Thunderbird back to normal!