13.236.48.194
ec2-13-236-48-194.ap-southeast-2.compute.amazonaws.com
52.64.190.209
ec2-52-64-190-209.ap-southeast-2.compute.amazonaws.com
54.253.253.225
ec2-54-253-253-225.ap-southeast-2.compute.amazonaws.com

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