Email Header Analyzer

Paste the raw headers from an email (Gmail: "Show original"; Outlook: "View source") to see how it authenticated. SPF checks the sending IP is allowed for the envelope domain, DKIM verifies a cryptographic signature, and DMARC ties them to the visible From: domain and says what to do on failure.

Everything is parsed locally in your browser. The headers you paste are never uploaded. The Received path is reversed so the originating server is at the top.