proxy-ipv4.3.192.send-mail2.xyz has no MX records.
Question and response
Question
dig proxy-ipv4.3.192.send-mail2.xyz. MX
Answer
The response has no answer records.
Authority
send-mail2.xyz. 1800 SOA ns1.digitalocean.com. hostmaster.send-mail2.xyz. 1738764931 10800 3600 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0