Upgarde from 4.5.6 to 5.0B3

[Runner]

I upgrade from Centos 4.5 to 5.0 before upgrading from Zimbra 4.5.6 to 5.0B3. It apears that I can not send mail. Checked my logs and found that postfix is not running. Any suggestion on what to look for?

[Runner]

I found my problem, Sendmail on CentOS 5.0 was turned on and therefore using ports which Zimbra needed to use. I was checked the Zimbra logs but did not check the systems to see if any of the services had changed from the prior to the install of the OS.