frdsmtp.skillsoft.com has no CNAME records.
Question and response
Question
dig frdsmtp.skillsoft.com. NS
Answer
The response has no answer records.
Authority
skillsoft.com. 5287 SOA udns1.cscdns.net. hostmaster.cscdns.net. 7456 86400 86400 86400 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0