mx01.iso.afrinic.net has no MX records.
Question and response
Question
dig mx01.iso.afrinic.net. MX
Answer
The response has no answer records.
Authority
iso.afrinic.net. 1800 SOA ns1.afrinic.net. dnsmasters.afrinic.net. 2026022000 1800 1800 1814400 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0