Hi Alberto,
In Unity Connection, the Opening Greeting Call Handler is also a "Default" Auto Attendant. This will list all users that have gone through the First time Enrollment and recorded a Spoken Name. By default, dialing 4 from the Opening Greeting will take you to the Directory which can be searched via entering the name from the keypad or switched to use a Speech enabled style directory :)
Opening Greeting Acts as an automated attendant, playing the greeting that callers first hear when they call your organization, and performing the actions you specify. The Opening Greeting Call Routing rule transfers all incoming calls to the Opening Greeting call handler.
By default, the Opening Greeting call handler allows callers to press * to reach the Sign-In conversation, or press # to reach the Operator call handler. Messages left in the Opening Greeting call handler are sent to the Undeliverable Messages distribution list.
System Administration Guide for Cisco Unity Connection Release 7.x
Managing Call Handlers
http://www.cisco.com/en/US/docs/voice_ip_comm/connection/7x/administration/guide/7xcucsag060.html
Hope this helps!
Rob
