mx2.spamtador.com has no CNAME records.
Question and response
Question
dig mx2.spamtador.com. NS
Answer
The response has no answer records.
Authority
spamtador.com. 10800 SOA ns7.nsprimario.com. soporte.adw.es. 2026022504 10800 3600 86400 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0