As of LCOS version 9.24, you can optionally enable the signaling of new messages on SIP phones.
The LANconfig dialog under

has been modified as follows:
- Msg. Waiting (MWI) via
-
The presence of voice messages left on your provider's online mailbox are signaled by notifications on the device. Signaling occurs in different ways depending on the terminal type. Select the line for which this function should be enabled from the list of configured SIP lines under Note: Notification only occurs if the provider supports this function.
.