JPKCom DB

Mail Header Analyzer

Analyze email headers in your browser: delivery route and sending IP, SPF/DKIM/DMARC per server, spam filters and phishing hints — your way into the docs.

Make email headers readable — without anything leaving your browser

Every email drags along a block of technical headers that most clients keep hidden: where the message came from, which servers it passed through, whether it could prove it wasn't forged, and whether a spam filter flagged it. The Mail Header Analyzer makes exactly that block visible. Paste the raw headers (or the whole message), click Analyze, and the tool breaks them down into four views: findings and the key facts at a glance, the delivery route as a timeline, the authentication and spam results, and a searchable table of every header. Encoded subject lines and sender names show up as plain text along the way.

The key point: the whole analysis runs client-side, in your browser. No server ever sees your headers — and email headers in particular tend to carry sensitive details: internal server names, IP addresses, recipient addresses, subject lines. That none of it is uploaded is not a side effect here, it's the whole idea.

The tool is built for anyone who needs to get to the bottom of an email: admins and mail operators tracing why a delivery is stalling; developers checking their SPF, DKIM, and DMARC setup against real headers; support and security teams taking a suspicious phishing message apart; and anyone who simply wants to know why a message landed in spam or arrived hours late.

What the Mail Header Analyzer does — at a glance

  • Parse — paste raw headers or a whole message, upload a .eml or .txt file, or drop one in; Analyze gets you going. Example walks you through everything with a realistic message.
  • Overview — findings such as missing required fields, a display name hiding a different address, a Reply-To on a foreign domain, or failed authentication; plus the sender, the detected sending IP, the authentication and spam verdicts, and the central fields, decoded.
  • Route — the delivery path from the Received fields as a timeline from the moment the message was written to the mailbox, with IP classification, waiting times, TLS status, and total transit time.
  • Security — every Authentication-Results field on its own, clearly marked as either coming from your provider or potentially forged; plus Received-SPF, DKIM signatures, the ARC chain, and spam filter results from SpamAssassin, Rspamd, and Microsoft.
  • All Headers — every single header in a searchable table, decoded or raw, with copy and download functions.

Architecture: 100% in the browser, no backend

The Mail Header Analyzer has no server component. Parsing, route computation, authentication evaluation, and rendering all happen entirely in JavaScript in your browser. There is no API, no upload endpoint, no server-side caching. Even the file upload and drag-and-drop read the file locally through the browser's FileReader API — the file is never sent anywhere.

Because email headers can contain personal and confidential data, that's a real privacy advantage over the many online header analyzers that ship your headers to a third-party server. By default, nothing is stored: the tool keeps a local history in your browser only if you explicitly switch it on — and even then only the header section, deleted with a single click. And because headers come from foreign, often malicious messages, the tool outputs every value as text only, never as HTML. Details are in the manual.

Try it now

→ Open the Mail Header Analyzer — paste headers, click Analyze, done. No account, free, right in the browser. If you don't have a real email handy, the Example button loads a realistic sample header and analyzes it straight away.

  • DNS, SSL, Redirect & URL — check the DNS records behind SPF, DKIM, and DMARC once the analyzer points to a problem.
  • IP tools — dig deeper into a sender or relay IP from the Received lines: calculate its subnet, identify special-purpose ranges, convert the address format.
  • Hash generator — compute checksums, for instance to compare a downloaded header file against the original.

There's more on the sub-pages: the manual with every tab and parsing rule, real-world examples, and collected tips & tricks.