ostlibsmtp10-01.test.phx3.secureserver.net has no CNAME records.
Question and response
Question
dig ostlibsmtp10-01.test.phx3.secureserver.net. NS
Answer
The response has no answer records.
Authority
secureserver.net. 3600 SOA cns1.secureserver.net. dns.jomax.net. 2026030207 300 600 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0