Notwithstanding Scotts comment, I was thinking of the case of SIDF
where there is an arbitrary Sender field.
Wouldn't the propspec cover that?
In this case, the policy checked is that of the domain from the
RFC2822 Sender field and not the domain of the RFC 2821 Mail From
So one would be header(_dot_)sender=foo(_at_)bar, the other would be
smtp(_dot_)from=foo(_at_)bar (and moreover it would be spf=pass vs.
sender-id=pass), so a parser could definitely tell what got evaluated.
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