Are you talking about a pop or imap mail account ? Are you talking about more than one mail account?

I'm presuming you can see the Folder Pane. Do you have this setting:

• Menu icon > Folders > All

If IMAP: Right click on imap mail account name in Folder Pane and selct 'Subscribe' Do you see list of all folders ? click on 'Refresh' Are you able to select/highlight all required folders? If yes, select them and click on 'Subscribe' click on 'OK'

Thanks, that was really helpful and I think I have now recovered all my missing folders! Although I think I did try this before but it didn't work, but it has worked this time. Many thanks.