def _MXTranslation(rdata, origin):
  """Returns the translation of the given MX rdata.

  Args:
    rdata: Rdata, The data to be translated.
    origin: Name, The origin domain name.

  Returns:
    str, The translation of the given MX rdata which includes the preference and
    qualified exchange name.
  """
  return '{0} {1}'.format(rdata.preference, rdata.exchange.derelativize(origin))