I'm somewhat confused by your post and it is slightly misleading.
Originally Posted by dogatemycomputer
Zimbra does not require Postfix to be installed in your operating system, ZCS has all the components it needs when you install it and that includes a copy of postfix. The steps you've described above are not required, all you've done there is install a copy of postfix then start it then restart Zimbra which won't run because postfix (the operating system version) is installed and running. You then stop the o/s version of postfix, switch to the zimbra user and start ZCS (which includes it's own copy of postfix) and that works - you simply didn't need to install postfix. ;)
As I said.. this solution is not for everyone. I made it clear the OS version of Postfix was disabled, Sendmail was disabled and restarting Zimbra would not load Zimbra's copy of Postfix. I needed to get the mail server up and running. Disabling sendmail and restarting Zimbra did not help but installing a fresh copy of Postfix resolved the problem. In light of your comment I may still go back and try to understand why Zimbra would not start Postifx and why installing a fresh copy fixed the problem or try reinstalling Zimbra's bundled version.
Originally Posted by phoenix
In any case I will concede that a less experienced tech may be in serious trouble if they have a broken copy of Postfix installed so they try installing a second copy which could make things worse.