o1.sendgrid.kubra.com has no CNAME records.
Question and response
Question
dig o1.sendgrid.kubra.com. NS
Answer
The response has no answer records.
Authority
kubra.com. 751 SOA pdns112.ultradns.com. admin.kubra.com. 2023057467 3600 900 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0