Email Headers Explained: How to Read Them and Detect Suspicious Emails
Learn how to read email headers, understand SPF, DKIM, and DMARC results, and identify suspicious or phishing emails using header analysis.
Introduction
Every email contains hidden technical information called email headers. While most users never see them, headers play a crucial role in email security, authentication, and troubleshooting.
Understanding email headers helps identify phishing attempts, spoofed messages, and delivery issues — making it a valuable skill for businesses and IT professionals.
What Are Email Headers?
Email headers are metadata added to every email as it travels from the sender to the recipient. They include information about sending servers, authentication results, timestamps, and routing paths.
Headers are used by email providers to evaluate trust and decide whether a message should be delivered, flagged as spam, or rejected.
Key Information Found in Email Headers
- Sending IP address and mail servers
- Email authentication results (SPF, DKIM, DMARC)
- Routing path between servers
- Timestamps for each delivery step
How to Read SPF, DKIM, and DMARC Results
Authentication results are usually displayed as:
- SPF: pass, fail, or softfail
- DKIM: pass or fail
- DMARC: pass, quarantine, or reject
If any of these checks fail, the email may be considered untrusted.
You can verify authentication independently using:
How Email Headers Help Detect Phishing
Phishing emails often reveal inconsistencies in their headers, such as:
- Mismatch between sender domain and sending IP
- Failed SPF or DKIM checks
- Unusual routing paths
- IP addresses with poor reputation
Checking the sending IP with an IP Reputation Checker can help determine whether the email originated from a trusted source.
When Email Headers Are Useful
Email header analysis is commonly used for:
- Investigating phishing incidents
- Diagnosing email delivery problems
- Verifying authentication configuration
- Security audits and compliance checks
Best Practices for Businesses
To make email header analysis effective:
- Ensure SPF, DKIM, and DMARC are properly configured
- Monitor IP reputation regularly
- Educate employees to report suspicious emails
- Use auditing tools to detect issues early
Conclusion
Email headers provide valuable insight into how messages are sent, authenticated, and delivered. Learning how to read them helps businesses improve email security, detect phishing attempts, and maintain domain trust without relying solely on automated filters.