[CentOS] zimbra test

I wanted to test zimbra on centos 6 (I'm new to centos).  While installing
zimbra it said there was a conflict on port 25.  So I found out that
postfix is the default mta on centos.  I then did sudo yum remove postfix
and followed the prompts for removing it, but in doing so it removed chrome
that I had installed and several other packages that seem to be important.
Some of these were cron, some lsb packages, and some others.  Why does
removing postfix remove these others.  cron and the others are dependent on
having postfix?  Seems odd if they are.

Thanks,

-wes