smtp.rapidswitch.com has no CNAME records.
Question and response
Question
dig smtp.rapidswitch.com. NS
Answer
The response has no answer records.
Authority
rapidswitch.com. 4712 SOA ns2.rapidswitch.com. hostmaster.rapidswitch.com. 98 3600 120 1209600 10800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0