> DMARC = telling receivers how to handle mail that fails authentication.
No. DMARC is about if the from address has to match the address used in dkim/spf
No. DMARC is about if the from address has to match the address used in dkim/spf
DMARC is primarily about "alignment" (switching SPF from caring about the envelope sender to instead using the from header). Yes, it does also tangentially address those other points, but the primary reason it was adopted was to prevent spoofing of from headers (where in original spf that was a non-goal)