Tools
Email header analyzer
Paste the raw headers of any email (Gmail → Show original, Outlook → View Source). We parse the authentication verdicts the receiver assigned, the envelope fields, and the hop trace from sender to recipient. Runs entirely in your browser — no data leaves the page.
How to get raw headers
- Gmail — open the message, click the three-dot menu in the top-right, choose "Show original". The page that opens has a "Copy to clipboard" button at the top.
- Outlook (desktop) — open the message, File → Properties → "Internet headers".
- Outlook (web) — open the message, three-dot menu → View → View message source.
- Apple Mail — View → Message → All Headers (or ⌘⇧H).
- Thunderbird — View → Headers → All; then right-click the message → View Source.
What the Authentication-Results header tells you
The receiver writes its own Authentication-Results header naming itself and recording every authentication mechanism's verdict: spf=pass, dkim=pass, dmarc=pass or their failure variants. This is the most directly useful signal in the headers — it is the receiver telling you, on the record, whether your mail authenticated properly.
Sending email yourself?
SNDR's outbound MTAs handle SPF, DKIM, DMARC alignment, and add the headers receivers want to see — automatically per send. Start free.