How do we identify a website-specific IP address?

And in addition, can each Email output be provided through the website’s own private IP address?
How can that happen?

I’m sorry , I don’t understand what you wanna say here ?

I want to define a private IP for cyberpanel.
So some sites need to be on another IP address.

You can do that by manually setup listener in OLS webadmin console

Is there a source available?
How Can I do that?
And will this feature be added?

CyberPanel by default now uses only 1 IP. So you will have to do this manually. This guide can serve you well: [Tutorial]How to add 2nd IP for websites — CyberPanel - WebHosting Control Panel for OpenLiteSpeed