mx1.sat.rackspace.com has no CNAME records.
Question and response
Question
dig mx1.sat.rackspace.com. NS
Answer
The response has no answer records.
Authority
sat.rackspace.com. 24 SOA ns.rackspace.com. hostmaster.rackspace.com. 1699466605 300 300 1814400 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0