ns3.ubivox.org has no MX records.
Question and response
Question
dig ns3.ubivox.org. MX
Answer
The response has no answer records.
Authority
ubivox.org. 1800 SOA joan.ns.cloudflare.com. dns.cloudflare.com. 2397645103 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0