Alright, I'm running the Open Source version on Centos 4. I was asked to add LDAP authentication to the servers and realized Zimbra is already running LDAP.
Following the instructions on the UNIX and Windows Accounts in Zimbra LDAP and Zimbra Admin UI - ZimbraWiki page helped me get started, however, here is the problem.
I am not running Samba, so I skipped all the Samba related parts of this.
The problem is that now a single new extension has appeared, and it says 'Posix Groups' and when I attempt to create a new group I get:
Message: system failure: createLDAPEntry
Error code: service.FAILURE
Also, authentication breaks if I use LDAP. (When I set LDAP in authconfig)
Do I need Samba to do Linux account administration in Zimbra or am I missing something?