Hello there Gjveerman. The folders might be corrupted, or the index file itself is broken. Are they still visible?No? It might help to run the 'Repair Folder' function on the Inbox folder.This is the fastest way to recover them if the folders exist but are simply not being displayed. '''''Here’s how''''' Files might be collapsed. Click the '>' or '+' icons next to the Inbox in the left pane to expand the folders. The next step is to verify your IMAP folder subscriptions. Right-click your email account, select 'IMAP Folders' (or 'Subscribe'), and click 'Query'. Locate the missing folders in the list and ensure they are subscribed to restore visibility. '''''Here’s how 2''''' Right-click on Inbox > select Properties. Click the Repair Folder button and then click OK. Thunderbird will now rebuild the index.Did anything specific happen recently that might have caused this?