mx2.sat.rackspace.com has no CNAME records.
Question and response
Question
dig mx2.sat.rackspace.com. NS
Answer
The response has no answer records.
Authority
sat.rackspace.com. 2 SOA ns.rackspace.com. hostmaster.rackspace.com. 1699466605 300 300 1814400 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0