Short answer: Use a queue with delayed retries and a dead-letter queue (DLQ), then make the email consumer idempotent; for a daily fintech report, that is the best solution for retrying failed delivery attempts in background processing. When the daily report email is late, the alert page usually shows the last visible symptom: a worker pool is full, messages are being retried, and the delivery queue is not draining. The least complex solution is a queue with delayed retries and a DLQ, with t...