Question 1

What are email headers?

Accepted Answer

Email headers are metadata fields prepended to every email message. They record the path the email took from sender to recipient, authentication results (SPF, DKIM, DMARC), timestamps, sending software, and anti-spam verdicts. Headers are not normally visible to end users but are essential for diagnosing delivery problems.

Question 2

How do I get the raw headers of an email?

Accepted Answer

In Gmail, open the message, click the three-dot menu and choose 'Show original'. In Outlook, open the message, go to File > Properties and copy the 'Internet headers' field. In Apple Mail, use View > Message > All Headers. You can paste either the headers alone or the complete raw email — the body will be automatically ignored.

Question 3

What is the hop chain?

Accepted Answer

Each time an email passes through a mail server, that server prepends a 'Received:' header recording where it came from, where it is going, the protocol used, and a timestamp. The hop chain shows these servers in chronological order (oldest first), with the delay between each hop. Unusually long delays identify slow or overloaded servers.

Question 4

What do SPF, DKIM and DMARC results in the headers mean?

Accepted Answer

The Authentication-Results header records the outcome of SPF (was the sending IP authorised?), DKIM (was the message signed and unmodified?), and DMARC (do SPF/DKIM align with the From domain?). A 'pass' for all three is ideal. 'fail' or 'none' indicates a configuration problem that can cause emails to land in spam or be rejected.

Question 5

How can I use header analysis to debug email deliverability issues?

Accepted Answer

Header analysis reveals exactly where an email was delayed, which server rejected or modified it, whether authentication passed at every hop, and which anti-spam systems flagged it. Look for large delays in the hop chain, 'fail' in Authentication-Results, a high X-Spam-Score, or unexpected relay servers that suggest a misconfigured mail infrastructure.