Thanks, I will have a look into it but I don't think I have been hacked as I am sure the Trash Folder only started being different when Yahoo changed the email a few months ago.
When you say your Trash is working all right, can you delete something into the Trash folder and it will stay there until you decide you want to delete it out of the Trash folder, or do you go back and have a look and there isn't actually anything left in the Trash folder as it has automatically been deleted?