dns3-rs.midco.net has no MX records.
Question and response
Question
dig dns3-rs.midco.net. MX
Answer
The response has no answer records.
Authority
midco.net. 900 SOA dns4.midco.net. hostmaster.midco.net. 2018117011 10800 3600 2419200 900
Additional
. 0 OPT ; payload 1220, xrcode 0, version 0, flags 0