ok, so KDE 4.7 is out.
After updating to 4.7, kmail complains on startup (which takes ages, btw) that “the server does not support TLS”. It sure would help to know which server. It also would help to be able to get at my mails at all; all my folders are completely empty. Oh, and deleting a mail from one of the folders that are not empty doesn’t work either.