A useful postmaster runbook starts with evidence collection.

Record:

  • sender/recipient;
  • exact time and timezone;
  • Message-ID/queue ID;
  • full SMTP response;
  • source/destination systems;
  • raw headers where delivered.

Then branch by symptom: rejection, delay, missing message, authentication failure, TLS problem, suspected abuse or mailbox/client issue.

Include where logs live, who owns DNS/gateways/providers and the escalation path.

Avoid documenting passwords or sensitive secrets in the runbook.

Reference material