This behaviour is not typical for the RadOutlookBar. You can try to set the SelectedContent in the SelectionChanged event handler instead of using 4 RadTreeViews in XAML. In these event handler you can set the details to be shown on the right of the OutlookBar too.
We recently created a feature request in our PITS related to this scenario. You can vote for it in order to increase its development priority.
the Telerik team
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