gateway.mcmtelecom.com.mx has no MX records.
Question and response
Question
dig gateway.mcmtelecom.com.mx. MX
Answer
The response has no answer records.
Authority
mcmtelecom.com.mx. 1200 SOA dns.mcmtelecom.com.mx. dominioscor.mcmtelecom.com.mx. 2026020602 3600 600 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0