Email Header Definition and Details

Wondering what an email header is?

Definition of an Email Header

Email Header lines make up the first part of any email message. They contain information used to control the message and its transmission as well as metadata such as the Subject, origin and destination email addresses, the path an email takes, and maybe its priority.

Header lines are normally not shown raw and in full by email programs. Only certain information—the Subject line, sender and sent date, for instance—is displayed, formatted for easy use.

In the SMTP standard (as opposed to general email parlance and use in email programs), the header is essentially only the destination of the email message.

Also Known As: header, e-mail header