John Levine wrote:
How does a receiver know the difference between a "mailer" and a
"random third party"?
It doesn't, and it doesn't care. It looks up the signing domain in
its handy local list of signers worth paying attention to. Maybe at
some future time there will also be external sources of worthy
signers, but that's way outside the scope of any discussion here.
Which handy local list of signers is that? Where do I find Cisco's?
Mike
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