nsa2.srv53.net has no MX records.
Question and response
Question
dig nsa2.srv53.net. MX
Answer
The response has no answer records.
Authority
srv53.net. 1800 SOA ns1.srv53.net. support.dnshosting.org. 1590167505 1800 600 2419200 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0