Well, I thought I just got into grips with KMail after setting up several IMAP accounts, retrieving folders' contents, and successfully sending mails.

But not yet..
Lately I am experiencing KMail endlessly processing/updating mail folder's contents (= spinning gearwheel) – and in access configuration, the once saved and working locations for "trash", "sent items", "drafts", are gone for every ID.

Further, in the dialogs for "trash" the folder locations are empty, and I can't search or navigate in there anywhere. And though for every ID I can select the right default folders again – they will be lost on next startup.

Also (manually) updating mail folders during a session may fail.

So how to deal with that?