We have 4 email servers behind a Cisco ASA Firewall.
All 4 email servers have an internal ip address and their own unique public ip address.
EmailServer 1 192.168.13.2 220.127.116.11
EmailServer 2 192.168.13.3 18.104.22.168
EmailServer 3 192.168.13.4 22.214.171.124
EmailServer 4 192.168.13.5 126.96.36.199
Since it is behind the firewall, regardless of which email server we send from, the receiving email server sees all coming from the same public ip address(188.8.131.52) .
How do we set it up so that if we send emails from emailserver 1, the receiving email server will see 184.108.40.206 instead of 220.127.116.11? This goes the same for the other 3 email servers.