I am currently evaluating a Groupware solution and Zimbra looks really good.
My only concern is that Zimbra forces you to use its own versions of server applications - particularly Apache, OpenLDAP and MySQL.
I find this a little off-putting since it means I need to have 2 versions of each server application running.
The ones supplied by the OS (needed for System Administration and web applications) and the ones supplied by Zimbra.
Does the Zimbra Software only interface these apps via LDAP (OpenLDAP), HTTP/S (Apache), SQL (MySQL).
If this is so, then would it be easy to get Zimbra to use the OS supplied apps, negating the double up effect.