I have two CWP installations. and like to have a copy of all emails (inbound and outbound) on the second server as backup. should the first go down i still got all emails. that is the plan. Anybody got an idea? Or Solution?
You need to implement some form of load balancing as described here
http://www.linuxpcfix.com/postfix-load-balancing-and-high-availability-with-haproxy/ and https://www.haproxy.com/blog/efficient-smtp-relay-infrastructure-with-postfix-and-load-balancers/