wl164.sendgrid.net has no MX records.
Question and response
Question
dig wl164.sendgrid.net. MX
Answer
The response has no answer records.
Authority
wl164.sendgrid.net. 1800 SOA aisha.ns.cloudflare.com. dns.cloudflare.com. 2397382112 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0