rx.citynet.net has no MX records.
Question and response
Question
dig rx.citynet.net. MX
Answer
The response has no answer records.
Authority
citynet.net. 597 SOA dns0.citynet.net. hostmaster.citynet.net. 2025101000 36000 3600 86400 600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0