I am confused as to how this ip addres to domain associate works in postfix.
what i'm trying to accomplish is use the postfix mail server to mail outbound messages on different ip addresses. I'm not sure how this works
and i'm not sure how to accomplish what i'm trying to do. If i relay a message to be sent to my postfix instance1 set up for domain1.com on ip address xxx.xxx.xx and then set up another instance of postfix and do the same thing, so as to enable myself to send out over different ip addresses per domain.

cat /etc/hosts
192.168.1.81 squeezel.squeezel.com squeezel
192.168.1.82 squeezel2.squeezel.com