Practice and reference
Read the concept, then use a quiz, builder or checklist to make it stick.
First response goal
The goal is to reduce uncertainty quickly. Confirm the symptom, gather evidence, avoid risky assumptions and create a clear next action.
Do not make destructive changes just to see what happens. That is not troubleshooting. That is jazz with root access.
Checklist
- Confirm sender, recipient and timestamp
- Check MX routing
- Check SPF, DKIM and DMARC
- Read the bounce code
- Check mail queue and logs where available
- Check reputation and rate limits
- Give a clear next step
Useful commands
$ dig MX example.com +short
$ dig TXT example.com +short
$ grep sender@example.com /var/log/maillog
$ exim -bp | head
What good notes include
- The exact symptom and timestamp.
- The command or tool used to verify it.
- Relevant output, trimmed and sanitised.
- What was ruled out.
- Recommended next action or escalation reason.
Customer-safe summary
Explain what was checked, what was found, and what the customer can do next. Avoid dumping raw logs unless they help. Clear beats clever.