On 12 Sep 2014, at 18:27, Dave Crocker <dhc@xxxxxxxxxxxx> wrote: > By definition, p=reject enforces a semantic that requires the owner of > the rfc5322.From domain to have a relatively tight relationship with the > operator sending the message. > > IMO, it's quite reasonable to characterize this as conflating From: and > Sender:. > > What tends to be missed, throughout all of the discussions about dealing > with the effect on intermediaries such as mailing lists, is that most or > all of the mechanisms being discussed for intermediaries will work > equally well for bad actors... Indeed. I wonder if it might not simply make more sense to warn users that the information in the header fields cannot be trusted once they have been remailed by an exploder of any kind. This way, transparent MUA unwrapping of encapsulated list mail is a much more plausible solution. Cheers, Sabahattin