I try in a lot of ways to download the phonebook on my DP750.
The phonebook.xml is store in our Local Network, in the path : \192.168.7.11\01_Buero\ and this folder is protected with user and password.
I set this configuration on Global Phonebook XML Setting:
Global Phonebook Type : XML
Automatic XML Phonebook Download: Enabled, use HTTP
HTTP/HTTPS User Name: username
HTTP/HTTPS Password: password
Phonebook XML Server Path: 192.168.7.11/01_Buero/
Phonebook Download Interval: 5
There is something wrong?