z.ns.nu has no MX records.
Question and response
Question
dig z.ns.nu. MX
Answer
The response has no answer records.
Authority
nu. 7200 SOA catcher-in-the-rye.nic.nu. hostmaster.nic.nu. 1771969916 28800 3600 864000 7200
Additional
. 0 OPT ; payload 1452, xrcode 0, version 0, flags 0