52.17.113.73
ec2-52-17-113-73.eu-west-1.compute.amazonaws.com
52.215.59.91
ec2-52-215-59-91.eu-west-1.compute.amazonaws.com
54.217.126.73
ec2-54-217-126-73.eu-west-1.compute.amazonaws.com

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