KMail hallucinates mails in "account" folder

Hello kdepim users,

since recently KMail shows me a count of 1'000 (exactly) messages in the
top folder of my IMAP account (see attached screenshot).

I am pretty sure there are no messages at this level, and kmail will not
show anything in the header or message panes if i click on the topmost
folder.

Alas, this is not cosmetic. The automatic archiving does not work
anymore. While I can archive any folder of the account seperately,
archiving the whole account fails with an error message (translated back
from German):

Folder "imap-1" could not be archived. Downloading of a message to
folder "imap-1" failed.

(Der Ordner „imap-1“ kann nicht archiviert werden. Das Herunterladen
einer Nachricht in den Ordner „imap-1“ ist fehlgeschlagen.)

How do I get rid of those phantom messages?

Regards
Mara

_______________________________________________
KDE PIM users mailing list
Subscription management: https://mail.kde.org/mailman/listinfo/kdepim-users