ns2.r4ns.com has no MX records.
Question and response
Question
dig ns2.r4ns.com. MX
Answer
The response has no answer records.
Authority
r4ns.com. 600 SOA ns1.r4ns.com. office.gbshouse.com. 1720708736 3600 3600 86400 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0