How Header analyzer works

Every email carries an invisible log of its journey: which servers it passed through, at what time, and whether its sender was really allowed to write on behalf of its domain. This tool makes that log readable. It's what you look at when wondering whether a message is genuine, or why a send landed in spam.

Step by step

  1. 1 In your mail program, show the message source and copy its headers.
  2. 2 You paste them into the field provided.
  3. 3 The analysis appears: the message's route server by server, and the verdict of the three authenticity checks — SPF, DKIM, DMARC.

What to put in each field

  • Message headers *

* On Gmail: open the message, “⋮” menu then “Show original”. On Outlook: “File” then “Properties”. On Thunderbird: Ctrl+U. Copy the whole block of lines at the start, up to the first blank line.

Good to know

  • No credentials are asked for, and the message body is not needed — only its headers.
  • Three acronyms worth knowing: SPF checks the server was allowed to send, DKIM that the message was not altered on the way, DMARC what the domain asks to be done on failure.

Use this tool