107.21.92.49
ec2-107-21-92-49.compute-1.amazonaws.com
52.87.129.132
ec2-52-87-129-132.compute-1.amazonaws.com
54.211.32.46
ec2-54-211-32-46.compute-1.amazonaws.com

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