18.206.67.173
ec2-18-206-67-173.compute-1.amazonaws.com
34.225.128.186
ec2-34-225-128-186.compute-1.amazonaws.com
34.237.93.27
ec2-34-237-93-27.compute-1.amazonaws.com

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