KMail crash at startup

Kmail crashes immediately after startup and freezes. I cannot open my Emails.
Error message is “Sie haben keine Lese-/Schreibrechte für ihren Posteingangsordner”, in english “You don’t have read/write permission to your inbox folder”
I cannot read out the Kmail version since it freezes immediately.
Opensuse Leap 15.4, KDE 5.24.4, Qt 5.15.2, Kernel 5.14.21.
Is there any way to retrieve and rescue my Mails?