Why does my simple VSTO add-in for Outlook fail to find a Built-In tab?

Question

Hi,

I put together a simple VSTO add-in to add a group (iMIS) and a button (Committees) to the New Email Message tab. This is my VS design:

Image-1.png

I pulled the name of the tab from the 2016 Office fluent user interface control identifiers Zip (outlookmailitemcontrols.xlsx). VS recognizes it as a built-in tab.

When I tested my add-in, Outlook threw this error:

Image-2.png

Why can't this tab be found?

Thanks,

Terry Thiel

Answer 1

I found the answer. I needed to set the RibbonType property of the OfficeRibbon object to Microsoft.Outlook.Mail.Compose. Case closed.