ntp6.inx.net.za has no MX records.
Question and response
Question
dig ntp6.inx.net.za. MX
Answer
The response has no answer records.
Authority
inx.net.za. 60 SOA ns1.inx.net.za. ops.inx.net.za. 20534 28800 7200 604800 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0