General
Email Header
Metadata at the top of an email containing routing information, sender details, and authentication results.
Definition
Email headers are lines of metadata at the beginning of an email message containing routing information, sender/recipient details, and authentication results. Headers include From, To, Subject, Date, Message-ID, and technical data like Received, Authentication-Results, SPF, and DKIM signatures. Headers are typically hidden from users but are crucial for troubleshooting deliverability issues.
Pro Tip
When debugging deliverability issues, examine the full email headers to see authentication results and routing path.