Version: (using KDE 4.3.2) Installed from: Ubuntu Packages KMail could show an overview of the IMAP account (used disk space, quota, read/unread messages for the subscribed mailboxes) when you select the associated IMAP account folder. Right now (KMail 1.12.2) it shows an empty list of messages and an empty message pane. KMail has all the needed infomation: KMail uses it in the properties dialog of individual mailboxes.
Thank you for your feature request. Kmail1 is currently unmaintained so we are closing all wishes. Please feel free to reopen a feature request for Kmail2 if it has not already been implemented. Thank you for your understanding.
Instead of creating a new feature request, please confirm here if the wishlist is still valid for kmail2.