server3.mailix.mx has no MX records.
Question and response
Question
dig server3.mailix.mx. MX
Answer
The response has no answer records.
Authority
mailix.mx. 1800 SOA cruz.ns.cloudflare.com. dns.cloudflare.com. 2395666269 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0