52.63.107.180
ec2-52-63-107-180.ap-southeast-2.compute.amazonaws.com
54.253.54.52
ec2-54-253-54-52.ap-southeast-2.compute.amazonaws.com
54.66.104.28
ec2-54-66-104-28.ap-southeast-2.compute.amazonaws.com

au-smtp-inbound-1.mimecast.com.
au-smtp-inbound-2.mimecast.com.