If a NAT >> Port redirection is setup between a specific public IP Alias address (e.g. 184.108.40.206) to an internal private IP address (e.g. 192.168.1.10) on the ‘Single’ TCP port 25 for an email server, then if the internal email server initiates a SMTP session with a remote email server somewhere on the Internet, will the remote email server see the session coming from the IP alias address (220.127.116.11) or from the primary IP address (18.104.22.168)? If it doesn’t use the public IP Alias address (22.214.171.124) as the source address, then is there any other way of configuring the router to work in this way?
If you want to use the public IP Alias address (126.96.36.199) as the source address, please refer to the attachment to configure the “Open Port” rule to implement the scenario. The relevant mechanism of “Port redirection” and “Open Port” are different, you may have a try. 🙂