Collapse bar to a slim version, reorganizing the icons to be vertical without description but with hover over descriptions.

Approach to implement:

RadOutlookBar is minimizable by default.
Descriptions of the minimized RadOutlookBarItems can be achieved in WPF via:

<Style TargetType="telerik:RadOutlookBarItem" BasedOn="{StaticResource RadOutlookBarItemStyle}">
    <Style.Triggers>
        <DataTrigger Binding="{Binding RelativeSource={RelativeSource AncestorType={x:Type telerik:RadOutlookBar}}, Path=IsMinimized}" Value="True">
            <Setter Property="ToolTipService.ToolTip" Value="{Binding RelativeSource={RelativeSource Self}, Path=Header}" />
        </DataTrigger>
    </Style.Triggers>
</Style>

or by adding this trigger to the RadOutlookBarItem's ControlTemplate.Triggers