Malformed messages, and messages for a run or step that no longer exists, are recorded as dead letters and acknowledged immediately instead of being retried. Each automation dead-letter queue (events, actions, webhook processing) is consumed and writes the same record.

Open dead letters for your organisation appear on Automation → Health. You can Re-drive a recoverable message back onto its original queue, or Discard it. Both actions are audited.

Relay rows that stay FAILED on the automation outbox are not copied into this list; they remain on the outbox and show in the Failed relays count.

Transient send failures retry through the actions queue (max_retries is 3, so the fourth delivery is the last). After that the step is logged FAILED with the error. The run does not wait on a dead-letter queue.