← cd ~/tools
// tools/headers
Email header analyser
In Outlook, open the message and choose File → Properties (or View message details in Outlook on the web), copy the internet headers and paste them here. You'll get the route, the authentication results and Microsoft 365's spam verdict in plain English.
Runs entirely in your browser. Nothing you paste is sent anywhere.
Field meanings follow Microsoft's anti-spam message headers reference. Headers can contain addresses and IPs, which stay in your browser.