Trace a message through its email headers

How to use the workspace

1. Open the message source in your mail client and copy the header block, excluding the message body.
2. Paste into the analyzer and run it locally.
3. Review unfolded fields, Received hops, parsed times and reported authentication assertions.

A concrete starting point

Subject: Build notification
From: notifications@example.com
Authentication-Results: mx.example.net; spf=pass
Received: from relay.example.com by mx.example.net;

These deliberately incomplete sample headers demonstrate structure, not a verified route.

Read the result carefully

Header unfolding joins continuation lines into one field. Repeated fields remain visible. Routing delays depend on parseable timestamps and system clocks; missing or odd times deserve investigation rather than automatic blame.

Common mistakes to avoid

• Authentication-Results and Received-SPF values are reported, not independently verified.
• A sender can prepend untrusted headers. Decide where your trusted receiving infrastructure begins.
• Header contents can identify people, systems or internal addresses. Downloading or copying moves that information outside the workspace.

Limits & privacy

Up to 1 MiB of input, 2,000 header fields and 1,000 routing or authentication entries under the shared output budget. No network lookup or signature verification.