I am currently using CentOS 4 with LDAP/postfix/dovecot/spamassassin configured for mailing service (including the LDAP for PAM). And I want to extend the server to support Calendar service and someone recommended me to have a look at Zimbra.
I am testing Zimbra in a sandbox, and found it excellent for our task. However, the installation of zimbra will replace postfix/LDAP/dovecot/spamassassin on the original system. It is ok for a sandbox but will be a quite hard work for our production server. I read the Zimbra wiki but only found instructions about using external authenication with another LDAP server. Anyway I just do not want to move the LDAP service to another server. And furthermore I want to keep the original configured services as more as possible. Especially the LDAP service will support the PAM and several other web applications, changing of this will be a nightmare for me.
I just want to ask are there any suggestions for my situation?