Outlook has 2 types of windows it uses:

• Explorers – display folder views – to get it via Application.ActiveExplorer() method
• Inspectors – display open items.

• using WPF – http://blogs.msdn.com/b/chhopkin/archive/2009/02/24/using-wpf-windows-in-visio-add-ins.aspx
• enumerations – https://msdn.microsoft.com/en-us/library/office/jj229676.aspx?f=255&MSPPError=-2147217396
• Backstage callback signatures – https://msdn.microsoft.com/en-us/library/ee691833%28office.14%29.aspx?f=255&MSPPError=-2147217396#odc_Office2010Introduction2OutSpaceUI_DescriptionsAttributesChildInformation
• Custom ribbon help – http://www.codeproject.com/Articles/463282/Custom-Ribbon-Help-for-Office-VSTO-Add-ins
• Adding context menu to outlook – https://naimhamadi.wordpress.com/2014/07/15/adding-a-custom-context-menu-item-to-outlook-2013/
• Extending the User Interface in Outlook 2010 – https://msdn.microsoft.com/en-us/library/office/ee692172%28v=office.14%29.aspx (includes sample xml codes)