I've got a minimal VSTO Addin for Outlook 2010 with a ribbon. My only goal is to display a ribbon (created via designer) with no functionality. From what little I can tell from MSDN ribbons should just automatically be displayed by default, perhaps with tweaking ControlIdType/CustomId properties for tabs.
Alas, tweaking these properties does nothing -- Outlook loads and displays no tab. A simple message box displayed in the ribbon loader reveals it never is triggered. Additionally, I haven't seen any information resources (tutorials, walkthroughs, overviews, etc..) that say anything about needing to manually tell Outlook to display tabs.
To get your ribbon displayed, on the base ribbon in your code change the RibbonType
property to be Microsoft.Outlook.Explorer
.