I have been through this recently, and with alot of pain. Aristus is right, the EC2 IP block is blacklisted... So setting up a relay on ec2 is a bad idea. We ha

I have been through this recently, and with alot of pain. Aristus is right, the EC2 IP block is blacklisted... So setting up a relay on ec2 is a bad idea. We have our EC2 Mail server instance on EC2, then have relays setup on slicehost which works great.