31_3_173_081.ip.cesenanet.net has no MX records.
Question and response
Question
dig 31_3_173_081.ip.cesenanet.net. MX
Answer
The response has no answer records.
Authority
ip.cesenanet.net. 86400 SOA dns2.cesenanet.com. dnsadmin.cesenanet.com. 2014040611 86400 7200 2592000 172800
Additional
The response has no additional records.