Where is the standard/RFC? (Score 1)

The reason email on the internet exists at all is that there are standards for handling it that have gone through the RFC process to be accepted. When someone can point to a relevant standard specifying how email MUST be authenticated in a certain way and everyone does it the same way, then sites will be justified in refusing communications with others that don't follow the accepted standard. Until then it is all handwaving and vigilante activity - and mostly ineffective as well.