rr table contains more than one address record for the same
name (but with different addresses, of course), MyDNS will serve them up
in a random order each time.
Round robin is used only if all the address records found have an
value of `0'. If any of the records have an
aux value that is
non-zero, load balancing will be used instead. (See section 4.6 Load balancing.)
Note that MyDNS will also return multiple same-preference MX records in random order, to help equalize the load among same-preference MX hosts.