Using Sender: as the authentication key was suggested and ultimately abandoned during both DomainKeys (RFC 4870, the predecessor to DKIM) and Sender-ID (RFC 4406, pretty much never implemented) for this sort of reason.
Yup. The patent license didn't help, but the fundamental problem is that it didn't do what users needed it to do.
Regards, John Levine, johnl@xxxxxxxxx, Taughannock Networks, Trumansburg NY Please consider the environment before reading this e-mail.
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