Free tool · header analyzer
Paste a header. See who actually sent it.
We pull Authentication-Results, Received chain, DKIM-Signature, the source IP, and surface the SPF/DKIM/DMARC verdicts that actually decided whether the message landed in the inbox or the spam folder. All client-side — nothing leaves your browser.
Paste raw headers
In Gmail: message → “⋮” → Show original → copy everything above the blank line.
In Outlook: File → Properties → Internet headers.
We parse it all client-side. Nothing is sent to a server.
Waiting on input
Paste a header on the left.
We'll read it on the right.
We'll read it on the right.
Got a finding you don't want to chase?
Hand this off to Mailstinger.
We'll host the policies, rotate the keys, and watch the reports for you. One CNAME and you're done — no spreadsheets, no XML reading, no “what was this DKIM selector again?” moments at 4pm on a Friday.