o1.sendgrid.trackstreet.com has no CNAME records.
Question and response
Question
dig o1.sendgrid.trackstreet.com. NS
Answer
The response has no answer records.
Authority
trackstreet.com. 1262 SOA alan.ns.cloudflare.com. dns.cloudflare.com. 2397629632 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0