Glossary Term
Email Headers
Metadata attached to every email containing routing information, authentication results, and sender details.
What is Email Headers?
Email headers are metadata attached to every email that contain routing information, authentication results, and other technical details. While recipients rarely see them, headers are crucial for deliverability.
Important headers:
- From: Displayed sender address
- Reply-To: Where replies go
- Return-Path: Bounce address
- Received: Trail of servers the email passed through
- Authentication-Results: SPF, DKIM, DMARC results
- X-Spam-Status: Spam filter evaluation
- Message-ID: Unique identifier
Headers for debugging:
- Authentication failures (SPF=fail, DKIM=fail)
- Spam scores and trigger reasons
- Routing issues
Most email clients let you view headers via "Show Original" or similar options.
Why It Matters
- 1Reveal why emails go to spam
- 2Show authentication results
- 3Help diagnose delivery problems
- 4Contain routing and sender information
Related Tools
Related Terms
SPF (Sender Policy Framework)
A DNS record that specifies which mail servers are authorized to send email on behalf of your domain.
DKIM (DomainKeys Identified Mail)
A cryptographic signature added to emails that proves they came from your domain and weren't tampered with in transit.
DMARC (Domain-based Message Authentication)
A policy that tells receiving mail servers what to do when SPF or DKIM checks fail for emails from your domain.
Spam Score
A numerical rating indicating how likely an email is to be flagged as spam based on content and sender factors.
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