u511372.wl.sendgrid.net has no CNAME records.
Question and response
Question
dig u511372.wl.sendgrid.net. NS
Answer
The response has no answer records.
Authority
wl.sendgrid.net. 139 SOA aisha.ns.cloudflare.com. dns.cloudflare.com. 2397600118 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0