'''Q: '''Are you talking about an imap or pop mail account? '''Q: '''Have you recently and also how frequently, do you compact your Inbox whether this is automatically done by Thunderbird or whether you have done it manually? If you have not compacted then''' do not compact '''until the matter is resolved as at this stage you may have a corrupted folder. Do this: Create new folders and move all the emails you can see from Inbox into those new folders. Ideally, create several folders with suitable names and move emails into those folders for organising and storage. Then right click on 'Inbox' folder and select 'Properties' click on 'Repair Folder' button select another folder and then reselect the Inbox. What happens ? Do you see emails reappear in Inbox or not?