Correct procedure to upgrade postfix 2.7 or more

Hi, im doing a manual of how to install virtualmin in centos (im a relative new user of centos). Actually i have Postfix version 2.6.6 in the last version of centos. Virtualmin says this

Mail server Postfix is installed and configured.

Your Postfix version does not support per-domain outgoing IP addresses.

i compile and upgrade postfix 2.7 in server, but i lost automatly virtualmin configuration and get my mails bounces (diferent bounce codes so i think is every server fault), so i come here to see if someone of you have a manual or something like “how to install postfix 2.7 with virtualmin configuration”. I normally when buy servers, ISP give me just the centos fresh install, and normally i have to do some steps like changue hostname, then remove httpd, then clean yum and after that i actually can install virtualmin, and some friends have the same problem thats why i want to do a easy to use manual with all normal errors (that i see in my friend group) and hope this help not just my group of friends, also to the next people that buy servers in this isp

Thx for readin and sorry for my bad english

You can upgrade centos 6 to Postfix 3 using ghetto
Detail available at;

cd /tmp/installations
rpm --import RPM-GPG-KEY-gf.el6
rpm -Uvh

use yum shell
yum shell --enablerepo=gf-plus
remove postfix
install postfix3 postfix3-ldap postfix3-mysql postfix3-pcre

postconf smtpd_relay_restrictions=permit smtputf8_enable=no
service postfix restart

Check maillog for errors and correct then;
postconf compatibility_level=2
postfix reload