corp.sigecom.com has no CNAME records.
Question and response
Question
dig corp.sigecom.com. NS
Answer
The response has no answer records.
Authority
sigecom.com. 300 SOA master.dns.rcn.net. hostmaster.rcn.com. 2019022505 3600 600 604800 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0