I added KDE backported packages recently to gain access to a more stable version of KDevelop. However, now, Kontact/Kmail's search doesn't work anymore.

Where do I start to find out what's wrong?

The problem manifests itself that when in the Inbox folder, I type something in the search bar, no Emails will be shown. (Yes, searching for something where the email is definitely there.)

Kubuntu 12.04 LTS. Kontact version 4.13.

What I tried. akonadiconsole as suggested here. But I couldn't find a feeder as mentioned. More generally, isn't there a checklist or a general approach to debugging akonadi, nepomuk and Kontact?