How to use it
- Open the message and export its source: Show original in Gmail, Internet headers in Outlook, All Headers in Apple Mail.
- Copy everything from the first Received: line to the blank line before the body.
- Paste it in. Read the alignment findings first — they explain DMARC failures that the raw verdicts do not.
- Check the delivery path for hops holding the message; sustained delays mean receiver-side throttling.
Frequently asked questions
Are my headers uploaded anywhere?
No. Parsing happens in your browser and this page has no backend. Headers routinely contain recipient addresses and internal hostnames, which is exactly why.
DKIM passed but DMARC failed. Why?
Alignment. DMARC requires the DKIM d= domain to match your From domain. If your platform signs with its own domain, DKIM passes and DMARC still fails. Set up a custom signing domain.
What is a normal delivery time?
Seconds. Minutes of delay at a single hop usually means the receiver is rate-limiting a sender it does not trust yet.