Version: (using KDE KDE 3.5.6)
Installed from: SuSE RPMs
Using a disconnected IMAP account, there is a feature to show only folders that I have subscribed to ("Nur abonnierte Ordner anzeigen" in the German version; I do not know the precise English translation; it is the 3rd out of 5 options on the "general" tab of the configuration window for the account) does not work.
When I enable it and unsubscribe from some folders, they are still shown.
Works for me, you need to enable subscription in the account settings though.