jnb.afrinic.net has no MX records.
Question and response
Question
dig jnb.afrinic.net. MX
Answer
The response has no answer records.
Authority
jnb.afrinic.net. 3600 SOA ns1.afrinic.net. dnsmasters.afrinic.net. 2025043000 10800 3600 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0