That's great, Raj, I'll PM you soon.
Our knowledge of Zimbra is limited, we're very new to it. It took us a while to get it running. We fell at the tty required hurdle. Some near useless one line answers to the problem being 'comment out the line DEFAULTS requiretty' wasn't helpful because it didn't specify the file. Eventually we found out that it was /etc/sudoers. I still have no idea what visudo is.
We have installed all components of Zimbra, although we have LDAP running on our domain controllers. I connect to LDAP on both domains (not Zimbra) from our website to validate staff and students for certain areas of the site.
Perhaps we'll need a PHP cron job to scan for new accounts on the domains?