kumomta/docs/reference/kumo/make_queue_config/retry_interval.md

retry_interval

Messages are retried using an exponential backoff. retry_interval sets the base interval; if a message cannot be immediately delivered and encounters a transient failure, then a (jittered) delay of retry_interval seconds will be applied before trying again. If it transiently fails a second time, retry_interval will be doubled and so on, doubling on each attempt.

The default is "20 minutes".

kumo.on('get_queue_config', function(domain, tenant, campaign, routing_domain)
  return kumo.make_queue_config {
    retry_interval = '20 minutes',
  }
end)