I often wonder if spam protection would be better if more clearly displayed.
I know DKIM, SPF, DMARC aren’t “friendly names” but we could call them “Sender Valid”, “Email Valid”, “Handshake Accepted” or something and then maybe a “no outside links” and “no suspicious content” — 5 pip marks or green ticks to feel better about it?
Then you could also force-display the domain and page title following links, and warn against mismatching reply-to: addresses. Maybe even show some known technographics from the headers (“Sent via Marketo?”)
All that to say, systems like that would help against spam callers and scammers.