Read a message’s headers
Every email carries hidden headers: a record of each server it passed through, written newest first. This turns them into a route with times, so “why did this message take four hours?” has an answer you can point at.
- Runs entirely in your browser
- Works offline
- No upload
- No sign-up
- No watermark
Loading the tool…
How it works
- Copy the headers: “Show original” in Gmail, File → Properties → Internet headers in Outlook, Ctrl+U in Thunderbird.
- Paste them above and press Analyse.
- Read the route top to bottom — row 1 is the first server that handled the message — and look for the hop (one step from server to server) where the delay jumps.
Why nothing is uploaded
Every operation on this page is done by code running inside your browser tab, using the same engine that renders web pages. The file is read from disk into your tab’s memory, transformed there, and written back out as a download. It is never sent anywhere — not to us, not to a third party.
Verify it yourself
- Open your browser’s developer tools (F12) and select the Network tab.
- Load your file and run the tool.
- The only requests you will see fetch the tool’s own code — and, for a few heavy tools, their open-source engine from a public CDN — plus one small page-view ping to loreatec.jp (page address and title, nothing more). None of them carry your file.
Frequently asked questions
The route reads backwards. Why?
Because each server adds its Received line at the top, so the newest is first in the file. This page reverses them for you: row 1 is the first server that handled the message and the last row is the one that delivered it to the mailbox.
One hop took nine minutes. What does that mean?
The message waited in a queue. The usual cause is “greylisting”: the receiving server deliberately turns away the first attempt from an unknown sender and accepts the retry. That costs between five minutes and an hour and cannot be seen anywhere but here. A long delay at the same hop every time usually means the receiver is overloaded or is slowing down incoming mail on purpose.
Why is a delay negative?
Because the two servers disagree about the time. Mail servers with slightly wrong clocks are common and harmless in themselves; it only matters when the difference is big enough to make the times useless or to expire signatures.
What is the difference between this and the full message test?
This page works offline and only reads what is written in the headers, including the receiving server’s own SPF, DKIM and DMARC results. Checking those signatures again yourself needs the public keys, which live in DNS — that is what the online message test does: the same reading, plus the checks.