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Blacklist & DNSA free tool by NullFortis
Header Analyzer
Decode raw email headers
What is it?
Every email carries hidden technical headers — the hop-by-hop Received chain, and the Authentication-Results header where the receiving server records its own SPF/DKIM/DMARC verdict.
Why it matters
When something goes wrong — mail lands in spam, a bounce, an unexpected DMARC failure — the headers are the actual evidence of what happened, not a guess.
Impact if ignored
Without reading headers, a deliverability problem is just guesswork; reading them turns "this seems to be going to spam" into one specific, fixable finding.
Common use cases
- Diagnose why one particular message failed authentication
- Confirm a forwarding service preserved SPF/DKIM correctly
- Investigate a suspicious or phishing report