wl220.sendgrid.net has no MX records.
Question and response
Question
dig wl220.sendgrid.net. MX
Answer
The response has no answer records.
Authority
wl220.sendgrid.net. 1800 SOA aisha.ns.cloudflare.com. dns.cloudflare.com. 2397972214 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0