ns2.xfoneusa.net has no MX records.
Question and response
Question
dig ns2.xfoneusa.net. MX
Answer
The response has no answer records.
Authority
xfoneusa.net. 3600 SOA dns1.nts-online.net. admin.nts-online.net. 638182428 7200 1200 3600000 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0