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

max_age

Limits how long a message can remain in the queue. The default value is "7 days".

kumo.on('get_queue_config', function(domain, tenant, campaign, routing_domain)
  return kumo.make_queue_config {
    -- Age out messages after being in the queue for 20 minutes
    max_age = '20 minutes',
  }
end)