gw.emailmanager.com has no MX records.
Question and response
Question
dig gw.emailmanager.com. MX
Answer
The response has no answer records.
Authority
emailmanager.com. 60 SOA ns1.emailmanager.com. sysadmin.emailmanager.com. 2024071502 10800 86400 604800 60
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0