After the upgrade to KDE Application 16.12 kmail no longer displays mails for certain local folders for me. When waiting long enough I get the following error dislpayed: Unable to fetch item from backend (collection -1) : Unable to retrieve item from resource: Did not receive a reply. Possible causes include: the remote application did not send a reply, the message bus security policy blocked the reply, the reply timeout expired, or the network connection was broken. Any hint on how to debug this further is appreciated. I even completely rebuild the akonadi-database. However I am back at the same behaviour after a few days of usage. Marking the bug as major, as mails are no longer displayed, making kmail unusable.
As additional info this seems to be caused by duplicated messages in one folder (which get created via bug 322126). As soon as on tries to display such a duplicated message the content of this message will never be displayed. After such an attempt also no other message will get displayed until kmail is restarted.
I did not have that probelm for quite some time now. Therefore closing the bug.