Then try to run "kbuildsycoca5 --noincremental" (as user), maybe Akonadi finds the imap resource then. Otherwise I cannot help you currently, sorry. We are aware that the KDE Applications are outdated in 42.2 Beta1 and not ready yet, they will get updated in the (near) future. 16.08.0 only got accepted to Factory yesterday though. Please wait for newer packages in 42.2, though I'm not sure if we will submit 16.08.0 already or wait for 16.08.1.