Normally, the standard routing setting is used for the delivery of the messages to the users. The messages are delivered to the user the dialed recipient number was assigned to. For more information pleare refer the article Site Settings - Creating the Call Numbers
Should the users use her voice-mailbox about a common voice-mailbox number, the phone arrangement / gateway must transfer the "RedirectionNumber". The ixi-UMS Business Server must be configured for it.
In this case the number of the diversion device (phone) from ixi-UMS Business Server is evaluated.
In the LDAP data bank the phone number of the user must be put down.
Read for further information the article: Route by Redirection