MailAlign

Paste the raw headers of an email (Gmail: Show original; Outlook: View message source; Apple Mail: View > Message > Raw Source). MailAlign shows whether the From, Return-Path, Reply-To and DKIM d= domains line up (relaxed and strict), what SPF, DKIM, DMARC and ARC results the receiving servers recorded, every Received hop with its delay and public IP, and what each finding means. It makes no network lookups, and nothing you paste is stored or logged.

Raw email headers (max 64 KB; anything after the first blank line is ignored)

Received-SPF: pass (google.com: domain of bounces+1234@em.example-shop.com designates 167.89.12.34 as permitted sender) client-ip=167.89.12.34;
From: =?UTF-8?Q?Example_Shop_=E2=9C=A8?= <hello@example-shop.com>
Reply-To: Example Shop Support <support@example-shop.com>
Subject: =?UTF-8?B?WW91ciBvcmRlciBoYXMgc2hpcHBlZCDwn5qa?=
Date: Tue, 13 Oct 2026 15:14:07 +0000
Message-ID: <9xYzAbCdQ1S2T3U4V5W6Xw@geopod-ismtpd-14>
To: jane.doe@gmail.com
MIME-Version: 1.0
Content-Type: multipart/alternative; boundary="b1"

JSON API

curl -s -X POST 'https://mailalign.mike-tusa.workers.dev/api/analyze' \
  -H 'content-type: text/plain' --data-binary @headers.txt

Or send {"headers": "..."} as JSON. No key needed: about 30 checks per minute per IP from a shared daily pool. OpenAPI 3.1 spec

Free API key

No sign-up and no email. A key gives you about 100 analyses per month of your own, outside the shared pool. Send it as Authorization: Bearer <key> or X-Api-Key: <key> (MCP clients: add it as a header). The key is shown once; we keep only a hash of it, so it can't be recovered.

For AI agents

MailAlign is also a remote Model Context Protocol (MCP) server with one read-only tool, analyze_headers. Works with AI agents and assistants that can call an MCP server or a JSON API, for example Muse, Claude, ChatGPT or Cursor (descriptive only). Most MCP clients accept this config; some use a different format (for example, VS Code uses a servers key). Clients with a settings screen just need the URL https://mailalign.mike-tusa.workers.dev/mcp.

{ "mcpServers": { "mailalign": { "type": "http", "url": "https://mailalign.mike-tusa.workers.dev/mcp" } } }

With a free key, add "headers": { "Authorization": "Bearer <key>" } to the server entry (exact field name depends on the client). Machine-readable docs: llms.txt · OpenAPI 3.1 spec · MCP server card. MailAlign is not affiliated with, endorsed by or sponsored by Meta, Google, Microsoft or any email provider.

Privacy

Header text you submit is analyzed in memory and discarded when the response is sent. It is never written to storage, logs or analytics, and MailAlign makes no network or DNS lookups. Full privacy notice.