ns2.mailrelay3.com has no MX records.
Question and response
Question
dig ns2.mailrelay3.com. MX
Answer
The response has no answer records.
Authority
mailrelay3.com. 3600 SOA mailrelay3.com.mailrelay3.com. root.mailrelay3.com.mailrelay3.com. 2039470413 7200 3600 86400 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0