As usual, John has pretty well nailed the response, but there was one other part of your question (Mike) that I thought deserved explanation:
On Sat, Nov 21, 2020 at 7:14 PM John Levine <jo...@taugh.com> wrote: > In article <dcc265f9-a143-5093-eba0-94ee059c7...@mtcc.com> you write: > >If I'm a receiver who is going to be making some filtering decisions > >based on ARC, I see that it passed by some authenticator along the way > >which is fine, but my question is why I should trust that intermediary > >in general? > > The short answer is that you shouldn't, any more than you should trust > random DKIM signatures. > > This also means that ARC isn't useful if you don't have a reputation > system to tell you where the lists and other forwarders that might add > legit ARC signatures are. > On Sat, Nov 21, 2020 at 2:33 PM Michael Thomas <m...@mtcc.com> wrote: > > Or did I miss where ARC resigns the body? Or is there a tie in for ARC > with the mailing list's resigned DKIM signature for the new message? > The ARC-Message-Signature (referred to as the AMS) includes a signature over the newly modified message (headers & body) in a way very similar to a DKIM-Signature. But this does not solve the problem of a malicious forwarder that does a wholesale replacement of the (presumably) good content with spam. That's were your own reputation and content analysis has to come in. --Kurt
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