smtpld21.fortimailcloud.com has no CNAME records.
Question and response
Question
dig smtpld21.fortimailcloud.com. NS
Answer
The response has no answer records.
Authority
fortimailcloud.com. 120 SOA ns3.fortinet.com. mis.fortinet.com. 2026014388 10800 15 604800 120
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0