The from address is now accepting mail, if I wasn't clear in my first post. It looks like at least one other mailserver was rejecting email for the same reason.
I'm curious if you consider that anti-spam measure to be productive? It's on the aggressive fringe of anti-spam measures...
Imagine a pathologically idealistic, anti-religious, culturally-relativistic, iconoclastic, socially-irreverent, sociologically-progressive signature line here. Or don't.