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Email Header Analyzer

Headers contain the full delivery story of a message. You can see every server hop in the Received chain, the originating IP, timestamps for each handoff, the Return-Path used for bounces, and authentication results for SPF, DKIM and DMARC. Headers also show the Message-ID, the X

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Headers contain the full delivery story of a message. You can see every server hop in the Received chain, the originating IP, timestamps for each handoff, the Return-Path used for bounces, and authentication results for SPF, DKIM and DMARC. Headers also show the Message-ID, the X

This free Email Header Analyzer from KX Toolkit is part of our all-in-one online toolkit. It runs entirely in your browser, so your data never leaves your device for client-side operations. 100% free, forever - no paywall, no credit card, no trial.

How to use the Email Header Analyzer

  1. Paste your input - JSON, regex pattern, JWT, URL etc.
  2. Pick any flags or options the tool supports.
  3. Click the action button (Format, Test, Decode).
  4. Copy the result or download it as a file.

What you can do with the Email Header Analyzer

  • Format and validate API responses while debugging.
  • Test regex patterns against real input before deploying.
  • Decode JWTs to inspect claims and expiry.
  • Generate UUIDs for migrations, tests and seeders.

Why use KX Toolkit's Email Header Analyzer

  • Browser-based: Works on Windows, macOS, Linux, iOS and Android - no install, no extension.
  • Privacy-first: Client-side tools never upload your data; server-side tools delete files right after processing.
  • Mobile-friendly: Full feature parity on phones and tablets - not a stripped-down view.
  • Fast: Optimised for instant feedback. No artificial waiting screens, no email-gated downloads.
  • One hub for everything: 300+ tools across SEO, text, image, PDF, code, color, calculators and more - skip switching between sites.

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Related Developer Tools

If you find this tool useful, explore the full Developer Tools collection or browse our complete tool directory. KX Toolkit is built for marketers, developers, designers, students and anyone who needs a quick utility without signing up for yet another SaaS.

What information can I learn from an email header?
Headers contain the full delivery story of a message. You can see every server hop in the Received chain, the originating IP, timestamps for each handoff, the Return-Path used for bounces, and authentication results for SPF, DKIM and DMARC. Headers also show the Message-ID, the X-Mailer or User-Agent that sent it, and any spam filter scores added in transit. Together they tell you whether a message is genuine and where any delays occurred.
How do I read SPF, DKIM and DMARC results in the header?
Look for the Authentication-Results line. SPF=pass means the sending IP is authorized in the sender's DNS SPF record. DKIM=pass means the cryptographic signature matches the sender's public key, proving the body was not tampered with in transit. DMARC=pass means SPF or DKIM aligned with the From domain and the domain's DMARC policy was satisfied. A fail or none on any of these is a strong phishing indicator.
How do I trace where an email actually originated?
Read the Received headers from bottom to top. The bottom-most Received line is added by the originating server and shows the true sender IP. Each line above it represents the next hop until the message reached your mailbox. Geolocate that originating IP using a WHOIS lookup. If the IP location does not match the claimed sender, or if hops appear suspicious, the message is likely spoofed or relayed through a compromised host.
What headers help me debug delivery delays?
Each Received header is timestamped, so subtract the timestamps between adjacent hops to find the slow link. A long gap between two servers points to greylisting, queue backlog or a slow DNS lookup at that hop. Also check for X-Greylist headers from anti-spam systems and any Diagnostic-Code lines from delivery status notifications. The header analyzer visualizes these hops as a timeline so the bottleneck is easy to spot at a glance.
Can header analysis detect phishing or spoofed senders?
Yes, and it is one of the most reliable techniques. Compare the From address with the Return-Path and the originating IP. A real message from your bank will pass SPF and DKIM aligned with the bank's domain. A phishing attempt will usually show a mismatched Return-Path, a failing DMARC result, or an originating IP unrelated to the claimed brand. The analyzer surfaces these mismatches so non-technical users can spot fakes.
Is my email content visible when I paste a header into the tool?
No. You should paste only the header section, which contains routing and authentication metadata but not the message body. Most mail clients have a View Original or Show Original option that lets you copy the header without the content. The analyzer never asks for the body, attachments or recipient list, and processing happens client-side where possible. Always strip personal data before sharing headers in a support ticket.

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