mail777.byseven.com.br has no MX records.
Question and response
Question
dig mail777.byseven.com.br. MX
Answer
The response has no answer records.
Authority
byseven.com.br. 300 SOA ns1-07.azure-dns.com. azuredns-hostmaster.microsoft.com. 1 300 300 300 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0