Akonadi after upgrade jessie->stretch

[Erwan David <erwan@rail.eu.org>]

Hi,

After upgrading from Jessie to Stretch, I would like to redo from start
my akonadi configuration. However I do not find how to do this. Worse,
launching kontact I get 2 dialogs, first one is "another mailer is
running do you want to import from it (but greyes out) and second one is
an error message "could not fetch resource" then nothing.

Another problem is I cannot edit the application menu (the right click
on the K button gives a menu but the "Edit Applications" entry does
nothing.

So if someone has an idea how to unblock this, I would be glad