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Why headers matter
SMTP adds Received lines, authentication results, and list-unsubscribe metadata. Analysts use them to spot spoofing, loops, and slow queues.
How to use this tool
Paste full headers (not just the body). Review parsed tables. Redact PII before sharing screenshots.
Use cases
Deliverability triage, phishing investigations, teaching mail flow, vendor SLA disputes.
Privacy and security
Editor and conversion workflows run in your browser without uploading your content to our servers for those steps. Clear sensitive data when you finish, especially on shared machines.