Setup 2 VPS for outgoing SMTP server behind a SMTP outgoing load balancer using postfix

We have a website that needs to send about 3 millions email messages (10 newsletters) per month (about 300000 users) using 10 postfix SMTP servers behind a SMTP outgoing load balancer server for one domain. All email messages will be sent from one address: noreply(at)ourdomain(dot)com. Currently, we have the 3 VPS servers: - 1 VPS for loadbalancer: 1 CPU core, 2GB RAM, 50GB storage. - 2 VPSs for outgoing SMTP: 1 CPU core, 1GB RAM, 25GB storage. Requeriments/Tasks: - You will have root access to all VPS servers. - You will have to work just on 3 VPSs, The load balancer and 2 SMTP nodes. We will work on the other nodes using your instructions. - All VPS have CentOS 7 installed. - We will give you the list of public and private IP addresses of each server. All VPS are in same LAN (the same data center) so they are reachable using private IPs. This way we save bandwidth because LAN bandwith is free for us. - Reverse DNS will be already configured for each server by our SysAdmin. - Install and configure Postfix on all servers and configure the smtp load balancer. No cpanel or similar are needed. All must be configured from the terminal using an SSH conection. - You will have to provide detailed information on how to install our SSL certificate on all servers. - Implement SPF, DKIM and similar techniques. All of these must pass on all major email services. - Create a technical document with all the steps and commands you executed on each server (load balancer server and SMTP server) so we can add more VPS servers to the pool of SMTP servers when we require more capacity. This is one of the most important task. This document will be used by our SysAdmin. We would like that our SysAdmin do the job in the future if we need to migrate to another provider so this manual must be as clear as possible so any SysAdmin can follow it up.