smarthost:
  driver = manualroute
  domains = ! +local_domains
  route_list = SMARTHOST_ROUTELIST
  # Let's not deal with "impossible" target IP addresses
  ignore_target_hosts = +bogusips
  # You don't want SMTP callouts through a smarthost, it probably won't work
  no_verify
  # If you're on a laptop, let's not freeze messages because the network is
  # down
  host_find_failed = defer
  # Optimization since the smarthost router is independent of the local part
  same_domain_copy_routing = yes
  transport = remote_smtp