This is *NOT* about protection or authentication, this is purely about
rfc822/2822/5322 message semantics. Something that has been well-defined
and constant for decades.
I have considerable sympathy in theory for your viewpoint, but in
practice, the Sender header was deprecated a long time ago. Most MUAs
ignore it, the few that don't display it in a way that just confuses people.
--
Regards,
John Levine, johnl(_at_)iecc(_dot_)com, http://jl.ly
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