VSTO Outlook: Customize email inspector header without using form regions

Question

When you open an email by doing double click on it, I would like to know is the top panel of the email (header - indicate in the screenshot with a blue rectangle -) can be customized by adding text or other controls. Also in the context menu that appears when you click on the three dots button, I would like to know if I can add some options there. If that possible. Below I attach a screenshot and I indicate there the places where I would like to place these things (see blue arrows).

Also I would like to do the same in the preview area where the mail is shown when you select it from the messages list.

Answer 1

No you cannot. Use a form region.

Answer 2

The Outlook extensibility model doesn't provide anything for customizing these bits. There is no trivial way to get the job done. The best what you could do is to develop a form region (Replacement or Replace-All) which can substitute the whole inspector UI, so you could re-build it from scratch. Read more about Outlook form regions in the Walkthrough: Design an Outlook form region article.

Also you may consider putting a form region with your custom information at the top of the window, but right below this pane. See Advanced Outlook view and form regions from Add-in Express.