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Email Header Analyzer & Parser

開発者

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入力

自動処理

出力

クライアント側

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ガイド

Email Header Analyzer & Parser

Parse and analyze raw email headers into a structured, readable format. Paste email headers to see the complete delivery path, authentication results (SPF, DKIM, DMARC), decoded MIME headers, spam analysis, and hop-by-hop timing. All processing happens in your browser — no data is sent to any server.

使い方

Paste raw email headers into the input area. The analyzer processes them instantly, showing a summary overview (sender, recipient, subject, date, originating IP), authentication results with color-coded pass/fail indicators, the complete delivery hop chain with timing between each server, and a structured table of all headers with decoded MIME values. Use the “Load Sample” button to see an example analysis.

特徴

Summary Overview — Parsed From, To, Subject (MIME decoded), Date, Message-ID, and originating IP address at a glance.
Authentication Results — SPF, DKIM, and DMARC status with color-coded indicators: green for pass, red for fail, yellow for softfail/none. Includes signing domain and policy details.
Delivery Hop Chain — Every Received header parsed into a visual chain showing from/by servers, timestamps, and calculated delay between hops. Highlights unusually long delays that may indicate issues.
MIME Decoding — Automatically decodes MIME encoded words (=?UTF-8?B?…?= base64 and =?UTF-8?Q?…?= quoted-printable) into readable text.
Spam Analysis — Parses X-Spam-Status, X-Spam-Score, and SpamAssassin rule hits. Provides an overall spam risk assessment.
Structured Header Table — All headers organized into groups (routing, authentication, content, custom/X-headers) with expandable long values.
Sample Headers — Load example headers to see the analyzer in action before pasting your own.
Reference Guide — Collapsible explanation of key email headers, SPF/DKIM/DMARC, Received header reading, and common spam indicators.

Email Authentication

SPF (Sender Policy Framework): Verifies the sending server is authorized to send mail for the domain. Checks the envelope sender against the domain’s DNS SPF record.
DKIM (DomainKeys Identified Mail): Verifies the email hasn’t been tampered with in transit using a cryptographic signature. The signing domain is checked against DNS.
DMARC (Domain-based Message Authentication): Builds on SPF and DKIM to specify what should happen when authentication fails (none/quarantine/reject). Provides reporting for domain owners.

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How do I find email headers?

In Gmail: open the email → click the three dots menu (⋮) → ‘Show original.’ In Outlook: open the email → File → Properties → ‘Internet headers.’ In Apple Mail: View → Message → All Headers. In Thunderbird: View → Message Source. The headers are the text block at the top of the raw message, before the email body. Copy the entire header section and paste it into the analyzer.

What do the Received headers tell me?

Received headers trace the email’s journey from sender to recipient. Each mail server that handles the message adds a Received header at the top, creating a chain you read bottom-to-top (earliest hop at bottom). Each hop shows which server received the message, from which server, and when. By comparing timestamps between hops, you can identify delays — a gap of several hours between two hops might indicate greylisting, queue delays, or suspicious routing.

What does SPF/DKIM/DMARC pass or fail mean?

SPF pass means the sending server’s IP is authorized in the sender domain’s DNS records. SPF fail means it’s not — the email may be spoofed. DKIM pass means the email’s cryptographic signature is valid and the message wasn’t altered in transit. DKIM fail suggests tampering or misconfiguration. DMARC pass means both SPF and DKIM align with the From domain. DMARC fail triggers the domain’s policy: ‘none’ (monitor only), ‘quarantine’ (spam folder), or ‘reject’ (bounce). All three passing is the gold standard for email authentication.

Is my email data sent to a server?

No — this tool processes everything in your browser using JavaScript. Your email headers never leave your device. There are no API calls, no server-side processing, and no data storage. This is important because email headers can contain sensitive information like internal server names, IP addresses, and routing details. All parsing, MIME decoding, and analysis happens entirely client-side.

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