ns2164.dns.dyn.com has no MX records.
Question and response
Question
dig ns2164.dns.dyn.com. MX
Answer
The response has no answer records.
Authority
dyn.com. 300 SOA ns1.p201.dns.oraclecloud.net. hostmaster.dyn.com. 4038 3600 600 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0