We are working on a new approach to display custom controls on E-mail, Task and Calendar dialogs in Outlook. We are using subclassing of the Outlook windows, which allows us to display our .NET controls in Outlook. This approach was working quite well until Microsoft created Social Connector plugin in Outlook 2010. There are some conflicts between the panels and sometimes the Outlook windows does not get redrawn.
We are trying to improve this mechanisms to avoid those problems. The improvement will based on the FormRegions which were introduced in Outlook 2007. This technology allows us to create your custom areas in Outlook dialogs. Also those areas might be displayed in the preview pane. As soon as those FormRegions are implemented right in the Outlook code there should not been any draw problems or conflicts with other addins.