I've been trying to set up a mail server on a rackspace CentOS 6 cloud server for the past couple days. I've followed your tutorial
to a tee with the exception that I didn't compile a new postfix with quota as I don't need a quota system.
Everything seemed to install perfectly, I did have to install some extra packages that weren't listed. But everything seemed to go well.
The issue I'm having is that I'm not able to send any mail (I haven't even tried receiving yet..). After looking at the maillog I can see that postfix gives me the error:
postfix/cleanup: warning: connect to mysql server 127.0.0.1: Access denied for user 'root'@'localhost' (using password: YES)
So, I'm guessing that postfix isn't using the .cf files I created with the proper user and password. I've triple checked all the files. The permissions are set properly, the vmail user is correct, mysql lets me log in with the mailadmin user and password, the aliases are set as you've listed, I can telnet to the smtp post and the pop3 port...