sp.domaku.com has no CNAME records.
Question and response
Question
dig sp.domaku.com. NS
Answer
The response has no answer records.
Authority
domaku.com. 2799 SOA ns1.nodoxy.com. hostmaster.domaku.com. 2026030501 10800 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0