Communications Express depends upon the following Sun Java System component products:
Access Manager (if you are using Sun Java System LDAP Schema Version 2)
You install Communications Express as a front-end server (in a multi-tier environment). The Messaging Server packages can then be configured to run as Webmail server, which connects to a back-end store running Webmail server. Also, both Communications Express and Messenger Express can run on different IP addresses.
In addition, you can configure Communications Express to have the Address Book on the front-end machine store its data either in the LDAP directory infrastructure or on an LDAP server other than the Communications Express machine. See the Sun Java System Communications Express 6.3 Administration Guide for more information.
Communications Express communicates with Calendar Server through the Calendar Server HTTP service, the mshttpd daemons for Messaging Server, and the LDAP service for address book. The cshttpd daemon, the mshttpd daemon can be local or remote, and the LDAP service can all be either local or remote.
When using a load balancer or port director type device, make sure to utilize “sticky” (persistent) connections such that users are continually routed to the same front-end server for the duration of their session.