s2.domainkey.u25078435.wl186.sendgrid.net has no NS records.
NS records for this zone are defined at wl186.sendgrid.net.
NS records for this zone are defined at wl186.sendgrid.net.
Question and response
Question
dig s2.domainkey.u25078435.wl186.sendgrid.net. NS
Answer
The response has no answer records.
Authority
wl186.sendgrid.net. 1800 SOA aisha.ns.cloudflare.com. dns.cloudflare.com. 2399841664 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0