gw.us.magento.cloud has no MX records.
Question and response
Question
dig gw.us.magento.cloud. MX
Answer
The response has no answer records.
Authority
magento.cloud. 900 SOA ns-1195.awsdns-21.org. awsdns-hostmaster.amazon.com. 1 7200 900 1209600 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0