News group architectures can work well for internal company functions such as on-line help, product planning, etc. And Exchange also supports directory access using the widely accepted LDAP protocol. LDAP is becoming very popular among developers, so I'm expecting more applications that will leverage Exchange in new ways. The directory structure and access methods are X.500 compliant. This means the Exchange directory can be used in global directory addressing schemes, again using the LDAP protocol.
Security is an interesting area in Exchange.
Exchange uses the Windows NT user account security to restrict access to mailboxes and folders. Exchange comes with its own optional key management server, should you wish to use encryption. Messages also can be digitally signed and authenticated with the aid of a certificate server. High availability wasn't ignored in Exchange. Clusters ensure that if one Exchange Server goes off-line, another Exchange Server continues serving so that users always have access.