How do I create HTML emails on Mac? I'd like to know the best way to create gorgeous mail templates such as Jumsfot's Stationary Mail ones and send them without having to use Safari.
Is there a way to do this easily?
I've tried this once, when Apple discontinued the iCards, but I wasn't able to do anything that looked nearly as good.

There is a tutorial here: The Graphic Mac

The full documentation is available at Apple's developer site.