Answer by nandoP for Should I put my email server in a public subnet or put in a private subnet and use load balancing / routing to route traffic from the internet?

ELB is good at HTTP and HTTPS, but can be problematic for other protocols..... for complete control over your load balancing / perimeter security, use an haproxy box with a public elastic ip, in combination with ec2 vpc security group rules and host based iptables