kumomta/docs/reference/events/get_egress_path_config.md

kumo.on('get_egress_path_config', function(domain, egress_source, site_name))

!!! note This event handler is in flux and may change significantly

Not the final form of this API, but this is currently how we retrieve configuration used when making outbound connections

The routing_domain parameter corresponds to the effective routing_domain of the originating scheduled queue. This will be the same as the recipient domain unless the message had set the routing_domain meta value.

kumo.on(
  'get_egress_path_config',
  function(routing_domain, egress_source, site_name)
    return kumo.make_egress_path {
      enable_tls = 'OpportunisticInsecure',
    }
  end
)

See also kumo.make_egress_path.