Why do callers with a suppressed number not hear the voicemail announcement of the called user?

A voicemail user A has forwarded to the voicebox. The user receives a call to his extension from a subscriber with a suppressed number. The caller without caller ID now enters query mode to the user's voicebox and is asked for the PIN for the user.

Behavior: A voicemail user redirects to his voicebox. Now the user receives a call to his extension from a subscriber with a suppressed number. The caller without number transfer is now asked for a PIN or extension number. However, the expected behavior would be to hear the voicemail greeting of the called party.

Solution 1: Stop the UM services in XPhone Server under UM > SERVICES. Now open the XCAPI configuration and switch to the CONTROLLER > "Controller name" > TWEAKS > STANDARD section. Add a new tweak called PREFERRED_IDENTITY and set the value to 1.

Save the setting and now start all UM services in XPhone Server under UM > SERVICES.

Solution 2: The subscriber redirects to the voicemail prefix number instead of the central voicemail number to activate his voicebox, see: https://help.c4b.com/de/xphone-connect-8/admin/index.htm#324.htm