us4.dns.ws has no MX records.
Question and response
Question
dig us4.dns.ws. MX
Answer
The response has no answer records.
Authority
dns.ws. 21600 SOA ns2.dns.ws. hostmaster.ns2.dns.ws. 2022101901 10800 3600 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0