Email header analyzer

Where to get the headers

• Gmail: open the message → three dots on the right → “Show original” → “Copy to clipboard”.
• Outlook: File → Properties → the “Internet headers” box.
• Apple Mail: View → Message → All Headers.

Paste the headers only — the body adds nothing to the analysis.

What happens to the text

Nothing. The headers are parsed on the fly and stored nowhere: not in a database, not in logs. The page contacts no external service — everything comes from what the message itself carried.

How to read the result

The route. Received headers are prepended, so they read bottom-up: the first row of the table is the very first server. The delay column shows how long the message sat at each hop. A long delay at the receiving end is almost always a reputation queue, not a slow network.

The checks. spf=pass means the server was allowed to send this message. dkim=pass means it was not altered in transit. dmarc=fail with both passing is the classic case: the From domain did not match the domain that passed (see alignment on the DMARC page).

List-Unsubscribe. Gmail and Yahoo have required it for bulk mail since 2024. Its absence is not a detail: without a proper unsubscribe button people press “spam”, and that hurts the domain far more.

Other checks

All three work without signing up and store nothing. For the bigger picture on deliverability see staying out of spam and Gmail limits.