Glossary
Email header
The lines of metadata at the top of a message: From, To, Date, Subject, Message-ID and the Received lines each server adds.
ValidReach Team · Updated 2026-10-26
In practice
Reading the full headers shows the path a message took and the results of SPF, DKIM and DMARC checks. Most mail apps have a “show original” option.
Verification and sending
Headers are how you debug a delivery problem after the fact. Verification works before sending.