Thanks again, falko.
At this point, all is fine, specially when I installed squirrelmail as my webmail apps. So my email users can read their emails thru the corporate webmail.
Now my next move is to import all the email users and create a temporary password for each from my old mail server to the new one. Then my next problem will be their old emails.
The configuration on the link you gave is somewhat the same as what I did on the two computers, the only difference is that I inputted the IP not the FQDN as what the sample config illustrates. I'll send you a network config diagram thru PM by tomorrow of my whole set-up.