mail-rz.computer42.org has no MX records.
Question and response
Question
dig mail-rz.computer42.org. MX
Answer
The response has no answer records.
Authority
computer42.org. 10800 SOA dns1.computer42.org. hostmaster.computer42.org. 2511171816 10800 3600 2592000 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0