3.224.26.124
ec2-3-224-26-124.compute-1.amazonaws.com
3.227.39.140
ec2-3-227-39-140.compute-1.amazonaws.com
34.205.38.235
ec2-34-205-38-235.compute-1.amazonaws.com

rx1.sparkpostmail.com.
rx2.sparkpostmail.com.
rx3.sparkpostmail.com.