>Option 1: Either what those providers has decided to do is >actually the right option or, because they are a family of 500 >pound gorillas, they are going to get their way and we need to >go along. If that is the correct or preferred way of looking at >this, then we should modify our servers to do what they like or >to work around the problems they create. We can have a WG try >to make minor improvements in (in this case) DMARC, but with the >understanding that anything that modifies the contents of >"From:" violates the definition and semantics of that field as >identifying the human message originator and noting that we've >got "Sender:" and "Resent-*" fields that are intended for >situations in which the last entity to inject the message into >Internet mail is not the same as the human message originator >and that we, like a few centuries of postal services before us, >made a distinction between envelope and message header >information for a reason. No idea how flexible mailman is, but how hard would it be to write some code that - detects if DMARC is in use - if so copies the original From header and other headers worth preserving to something like X-Original-From, etc. - and rewrites the From to a constant string: "This user mistakenly uses a DMARC protected system, see <some page that describes what is wrong>" <no-such-user@no-domain.invalid> Using a constant string maximizes the incentive to use a proper mail server.