Folder structure changed - 'more' folder has appeared

While deleting multiple e-mails from my inbox, I must have clicked something wrong, because the folder structure has changed. Below my account folder is one called ‘more’, and now my inbox and inbox subfolders are within ‘more’.

The folder ‘more’ cannot be moved, deleted or changed. Also, if I click on ‘more’, in the main area to the right of the folders it says there are no items in this folder, when plainly there are.

If I receive an e-mail, the ‘more’ folder disappears and the Inbox jumps back to where it should be, but after clicking on the subfolders, the ‘more’ folder reappears.

I also cannot move the inbox folder out of ‘more’. It shows a no-entry symbol if I try and drag it anywhere. What on earth has happened?

thanks,

Jon