Glossary
Email Header — Metadata Behind Every Message
Email headers are metadata attached to every message: delivery path, authentication results (SPF, DKIM, DMARC), timestamps, and Received hops. Recipients rarely see them — “Show original” in Gmail exposes the full chain.
What to look for
Authentication-Results, DKIM-Signature, Return-Path, and Received-SPF tell you why mail passed or failed filters.
FAQ
What header shows DMARC results?
Often Authentication-Results at major providers — plus per-hop SPF/DKIM in chain.
Can headers be forged?
Some fields can be spoofed — SPF/DKIM/DMARC exist to make spoofing detectable.
Where do I paste headers for analysis?
DomainPreflight Email tool — or read raw in your client’s “Show original”.