smtp3.avature.net has no MX records.
Question and response
Question
dig smtp3.avature.net. MX
Answer
The response has no answer records.
Authority
avature.net. 360 SOA ns-753.awsdns-30.net. awsdns-hostmaster.amazon.com. 1 7200 900 1209600 360
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0