When the control is in minimized state and the items do not have an icon, the headers are not visible.

This happens  whether there is available space in the active area are not. All items are rendered in the minimized area.

To work this around you can set the IsContentPreserved property after the control is loaded.


The fix for this issue will be available with the next LIB (version 2018.3.1224) expected on Monday, December 24.

As a workaround, you can add a custom Margin and Padding to the MinimizedOutlookBarItems:

<Style TargetType="outlookBarPrimitives:MinimizedOutlookBarItem">
    <Setter Property="Padding" Value="5" />
    <Setter Property="Margin" Value="2" />
</Style>

Where xmlns:outlookBarPrimitives="clr-namespace:Telerik.Windows.Controls.OutlookBar;assembly=Telerik.Windows.Controls.Navigation".

You can work this around by extracting the RadOutlookBar style and slightly modify it. You can find the Grid panel that holds the title and the minimize button and position the elements in different columns. 
 
<!-- Other XAML from the template -->
<Grid>
    <Grid.ColumnDefinitions>
        <ColumnDefinition />
        <ColumnDefinition />
    </Grid.ColumnDefinitions>
    <ContentControl x:Name="TitleElement" ContentTemplate="{TemplateBinding TitleTemplate}" Foreground="#FFDDDDDD"
                    FontWeight="Bold" HorizontalContentAlignment="Stretch" IsTabStop="False" Margin="5,3"
                    VerticalAlignment="Center" VerticalContentAlignment="Center"/>
    <telerik:RadToggleButton x:Name="MinimizeButton" Grid.Column="1"
                             IsChecked="{Binding IsMinimized, Mode=TwoWay, RelativeSource={RelativeSource TemplatedParent}}"
                             Style="{TemplateBinding MinimizeButtonStyle}">
        <telerik:RadToggleButton.Visibility>
            <Binding Path="IsMinimizable" RelativeSource="{RelativeSource TemplatedParent}">
                <Binding.Converter>
                    <telerik:BooleanToVisibilityConverter/>
                </Binding.Converter>
            </Binding>
        </telerik:RadToggleButton.Visibility>
    </telerik:RadToggleButton>
</Grid>
<!-- Other XAML from the template -->

Another approach is to use the ChildrenOfTypeExtensions.ChildrenOfType<T>() method to get the Grid and the minimize button, and add set the required properties. Here is an example:

private void outlookBar_Loaded(object sender, RoutedEventArgs e)
{
    var minimizeButton = this.outlookBar.ChildrenOfType<RadToggleButton>().FirstOrDefault(x => x.Name == "MinimizeButton");
    if (minimizeButton != null)
    {
        var parentGrid = minimizeButton.ParentOfType<Grid>();
        parentGrid.ColumnDefinitions.Add(new ColumnDefinition());
        parentGrid.ColumnDefinitions.Add(new ColumnDefinition());
        Grid.SetColumn(minimizeButton, 1);
    }
}

 Clicking on MinimizedOutlookBarItem when there is Visibility set to Collapsed on one of the items, the RadOutlookBar selects different item.

ItemTemplateSelector does not work. 

There is a workaround to extract the control template and edit the HeaderElement style with:
<ContentControl.ContentTemplateSelector>{TemplateBinding HeaderTemplateSelector}</ContentControl.ContentTemplateSelector>

The problem is fixed and will be available with Lib 2016.3.926.

The DisplayMemberPath property is not respected

Workaround:
Use an implicit style targeting RadOutlookBarItem instead of the DisplayMemberPath property. You can define the style in the xaml page (the view) where the RadOutlookBar control is defined.

<Window.Resources>
    <Style TargetType="telerik:RadOutlookBarItem">
        <Setter Property="Header" Value="{Binding ItemHeader}" />
    </Style>
</Window.Resources>

When the ItemsSource of the control is populated from a background thread, users are not allowed to manually set the position of the horizontal splitter.

Tab navigation is not working inside OutlookBar.

DECLINED: Duplicated with https://feedback.telerik.com/Project/143/Feedback/Details/113083-outlookbar-tab-navigation-is-not-working

If you set the SmallIcon property of a RadOutlookBarItem and you minimize the item the icon will not be visualized. Note that the icon is not visualized when a certain item goes in the popup.

The control is not translated in German

Reason for declination: 
The XAML team has recently reviewed this issue and it cannot be reproduced by following the described steps in our help:
http://docs.telerik.com/devtools/silverlight/common-localization.html#localization-using-built-in-resources
If you still encounter this issue and it is blocking for your work please contact us through the support ticketing system with details on your setup and a reference to this item. 

The ActiveItemsCount is not working

Provide visibility enumeration for the Overflow button "WhenNeeded", "Visible", "Hidden/Collapsed"

OutlookBar: Visual state of selected items in not correct

Add the posibilty for the RadOutlookBar control to have Width less than the specified MinWidth, when Minimized.

When the selected item is Collapsed, the RadOutlookBar still displays its content and Title

When the OutlookBar is minimized during run-time change of themes the text set to item's header overlaps the minimizing toggle button.

You can work this around by creating a custom control that derives from RadOutlookBar and override its OnApplyTemplate() method. Inside the method call the protected VisualStateChanged() method.

public class CustomOutlookBar : RadOutlookBar
{
	public override void OnApplyTemplate()
	{
		base.OnApplyTemplate();
		this.ChangeVisualState(false);
	}
}

Available in the R1 2017 SP1 Release.

Add a property which changes the minimize button orientation.

The Metro theme isn't properly applied on the RadOutlookBarItems if it is set in the RadOutlookBar definition:
<telerik:RadOutlookBar telerik:StyleManager.Theme="Metro" />