And as John said, there have been numerous proposals over the years of ways to annotate a message with what "standard" mutations were done so that at verification time the receiver could decide which mutations it was willing to forgive, but the community showed no interest in such complexities.
It is my impression that the proponents of this idea tended not to be very familiar with mailing list software and imagined that most mutations were simple, like adding a subject tag or a text footer. Those happen, but they are the very tip of the iceberg. Modern list managers add, delete, and reorder MIME parts, flatten HTML into text, and a huge list of other things that no mutuation catalog could plausibly describe.
That's one of the reasons that ARC doesn't try to say what's changed, just what the authentication results were before and after.
Regards, John Levine, [email protected], Taughannock Networks, Trumansburg NY Please consider the environment before reading this e-mail. https://jl.ly _______________________________________________ dmarc mailing list [email protected] https://www.ietf.org/mailman/listinfo/dmarc
