xx@mxt6.test.ex
  router = lookuphost, transport = remote_smtp
  host ten-1.test.ex [V4NET.0.0.1] MX=5
myhost.test.ex@mxt1.test.ex
  router = self, transport = remote_smtp
  host myhost.test.ex [V4NET.10.10.10] 
xx@mxt1.test.ex
  router = self2, transport = remote_smtp
  host myhost.test.ex [V4NET.10.10.10] 
xx@not.exist is undeliverable: Unrouteable address