Ribbons in Outlook 2007
Creating Ribbon customizations in Outlook 2007 is a bit different as in Word or Excel because Ribbon in Outlook is displayed when you open different Outlook inspectors and it's not a part of Outlook UI as it is in Excel or Word.
These customizations are loaded when a specific inspector is opened for the first time (this means that once you open up the inspector the ribbon is loaded and it can't be changed e.g. next time when you open the inspector). To enable/disable certain control on the Ribbon dependent on the context you need to use GetEnabled callback.
When an inspector is opened, Office calls GetCustomUI which passes in the string RibbonID. Checking the value (RibbonID) you can determine which inspector is displayed (in Word the RibbonID is Microsoft.Word.Document).
Table of RibbonIDs and corresponding message classes and example on how to enable/disable a control on ribbon can be found in VSTO v3 tutorial.
