mail4.imfr.cgi.com has no CNAME records.
Question and response
Question
dig mail4.imfr.cgi.com. NS
Answer
The response has no answer records.
Authority
imfr.cgi.com. 3335 SOA ns.cgi.com. dnsops\.gto.cgi.com. 787299475 1200 180 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0