{"success":true,"data":{"id":"missing-arc-seal-validation","label":"ARC seal absent on forwarded email (spoofed relay)","description":"ARC (Authenticated Received Chain) headers are added by mail forwarders and mailing-list managers to preserve DMARC authentication results across relay hops. A genuinely forwarded email always carries an arc-seal header stamped by the forwarding infrastructure. This signal fires when a message shows explicit forwarding evidence — a \"Fwd:\" / \"fw:\" subject prefix or a canonical body marker (\"-------- Forwarded message --------\" / \"Begin forwarded message\") — and has passed through 2+ Received hops, yet the arc-seal header is entirely absent. The combination strongly suggests the forwarding cues were forged: the email was never relayed through real forwarding infrastructure, it was simply crafted to appear forwarded in order to inherit the trust heuristics granted to forwarded mail. Guard: does not fire for senders matching the strict_invoice, strict_work, or strict_shopping allowlists, as known-good corporate forwarders sometimes omit ARC. Score: +3 trash.","tier":"danger","category":"header","isThin":false}}