Email Header
The email header refers to the section of an email message that contains essential information such as the sender, recipient, subject line, and more.
The email header is the top section of an email that includes sender, recipient, subject, and routing/authentication details.
Definition and examples
The “email header” refers to the section at the beginning of an email message that contains essential information such as the sender, recipient, sending time, and subject line. It also includes technical details that track the email’s journey across the internet while helping with email management and security. The full header records each hop and authentication check a message passes through from sender to receiver.
Why it matters
It matters because headers do more than label the message. They help inbox providers route and authenticate email, help recipients understand who the message is from, and help teams debug delivery issues when something goes wrong.
Common mistakes
A common mistake is mixing up the visible header fields a subscriber sees with the full technical header data behind the message. Both matter, but they solve different problems.
Related terms
Key takeaways
The email header is the top section of an email that includes sender, recipient, subject, and routing/authentication details
Full headers are especially useful when you need to troubleshoot delivery, routing, or authentication problems
Authentication results live in the header, so start there when debugging delivery
Related: Email body, Email footer, Subject line, Reply-to address.