An email header analyzer helps you decode what happened to a message in transit, including authentication checks and relay path details.
What to inspect in email headers
for SPF, DKIM, and DMARC outcomeschain for relay path and delay pointsand envelope sender alignment- Message ID and sending infrastructure fingerprints
Practical analysis checklist
- Capture full raw headers from the receiving mailbox
- Check authentication verdicts first (
,,,) - Compare sender domain alignment for DMARC
- Review relay hops to find latency or misrouting
- Confirm policy records (SPF, DKIM, DMARC) are current
Typical failure patterns
SPF softfail from unlisted sender IP
Often caused by unapproved sending systems or stale include lists.
DKIM fail due to selector mismatch
The selector in headers does not match the published DNS key.
DMARC fail despite SPF pass
Alignment can still fail when envelope and visible From domains differ.
Related tools and references
Automate header-based workflows
MailSlurp can parse inbound messages and route them with rules and webhooks. See email automation and routing for implementation options.