{"success":true,"data":{"id":"missing-date-header","label":"Missing Date header — RFC 5322 §3.6 violation; direct-to-MTA injection or bulk mailer stripping headers","description":"The email arrived without a `Date:` header. RFC 5322 §3.6 requires this header in every message, and every legitimate MTA (Postfix, Exim, Sendmail, Microsoft SMTP, Gmail's own submission path, the major ESPs) adds one automatically even if the submitting client forgets. A message without a Date header means either (1) direct-to-MTA injection from a compromised host or custom spam script that skipped the header, or (2) a bulk mailer deliberately stripping headers to obscure the send time (making timing-based filter rules harder to write). The check reads the RAW `headers['date']` field rather than the synthesized `msg.date` field because Gmail's API populates `msg.date` from the internal delivery timestamp when the real Date header is missing — reading `msg.date` would miss the header absence entirely. Weighted at +2 — not solo-decisive since some test-send tools and niche MTAs produce this shape legitimately, but extremely rare in normal traffic.","tier":"warning","category":"structural","isThin":false}}