notification.fortinet.net has no CNAME records.
Question and response
Question
dig notification.fortinet.net. NS
Answer
The response has no answer records.
Authority
fortinet.net. 300 SOA ns3.fortinet.com. mis.fortinet.com. 1 604800 7200 2419200 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0