what happens if you right click the folder, select properties and then the repair button.

Hi and thanks for your reply. I had already tried that with the result that all of the emails already there (irrespective of date) just disappeared. Luckily of course they are still available via Yahoo mail. Over to you if you will

I have just noticed that since doing the repair I have been deleting emails from the inbox and they do not appear in "deleted" as usual. I notice however that if I click on Properties it give the number of emails there (and the disc space used) Maybe this might give you a clue.

I am starting to think we should rename this support forum as the yahoo support site the level of trouble folks have with it basically overwhelms every other provider.

I have a yahoo account, the folder deleted mail goes to is called trash. But you apparently are looking for things in a folder called deleted. Perhaps that is the issue.

Yahoo folder names used on their web site do not reflect the folder names they use in IMAP, I have no idea why they do something stupid like that. It is just the sort of thing I have come to expect from Yahoo.

Not a Yahoo problem at all. I have now deleted and reinstalled Thunderbird and still have the same problem.