u2721515.wl016.sendgrid.net has no NS records.
NS records for this zone are defined at wl016.sendgrid.net.
NS records for this zone are defined at wl016.sendgrid.net.
Question and response
Question
dig u2721515.wl016.sendgrid.net. NS
Answer
The response has no answer records.
Authority
wl016.sendgrid.net. 1800 SOA aisha.ns.cloudflare.com. dns.cloudflare.com. 2399354377 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0