There are 12,434 employees worldwide at my company that are either
sales people or handle some sort of customer service where email is
'directed' to them.
I hope that you are not suggesting that DKIM is pointless unless you
already know the person that is sending to you.
Although... now that I think about it- I agree with you!
In my opinion, I am agreeing with you due to the lack of specific
rules covering who can and cannot sign for me and when/how do I expect
my policy to be enforced.
Actually, the problem is that spammers can sign mail. The mere
presence of a valid DKIM signature, on mail from a total stranger,
doesn't prove that mail isn't spam.
Of course I'm assuming that spammers don't subvert DKIM with zombies
that can send mail with the credentials of people you know. That
would be against the rules.
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