Registrar support for secondary entities is all but complete. Here's a first look:
Minor work remains to hook up the edit and delete callbacks (they work but for some reason they invoke on the parent entity).
I've also significantly extended support for authentication in the EmailMessage class and implemented a lot of robustness and diagnostic code. See Code Project.
In response to reader interest I've added support for authentication to the EmailMessage class. See Code Project.
Registrar support for secondary entities is coming along nicely. The header data and transforms are all sorted out and the foldout section headers work and look great. Now I need to put together a bunch of filter classes to provide the secondary entity data.
I've coded up reflection so that filter classes don't need explicit registration in the Registrar executable. This has been tested and works a treat. So there you go, Richo - no more remembering to update the viewer constructor.