14.2.4.2. Restrictions of Terminal Features 
The following entries must be deactivated on SIP terminals (either
in the DLS “Feature Availability” menu or on the terminal directly),
as these features are not supported by the OpenScape 4000:
- Log forwarded calls
- Call display name
- Music on Hold
- Message waiting
- Auto. reconnect
- Park
- Call park pickup
- Call back on busy (supported only with WL3/WL4 phones)
- Call back on no reply