monitoramento.sninternet.com.br has no MX records.
Question and response
Question
dig monitoramento.sninternet.com.br. MX
Answer
The response has no answer records.
Authority
sninternet.com.br. 3600 SOA ns3.sninternet.com.br. cgr.sninternet.com.br. 1604684219 3600 600 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0