text: #
  # compressed MX RDATA stored in an output buffer
  #
  # sentinel name: example.com.
  # 0  1  2  3  4  5  6  7  8  9 10  1  2 (bytes)
  #(7) e  x  a  m  p  l  e (3) c  o  m  .
   07 65 78 61 6d 70 6c 65 03 63 6f 6d 00
  # PREFERENCE: 10
    00 0a
  # EXCHANGE: compressed
  #(4) m  x ptr=0
   02 6d 78 c0 00
  