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