Outlook VSTO add-in won't run when you use Outlook view control from Web page?
Do you know that when you use the Microsoft Outlook View Control from a Web page, Microsoft Visual Studio Tools for the Microsoft Office System (VSTO) Outlook add-ins do not run.
This issue may occur even by this option: The Outlook View Control is not considered a part of the Outlook user interface. Therefore, the VSTO add-ins do not load correctly.
For more detailed information, please go through the following KB article.