Snom VoIP Phone - Manual (Page 33)

Advanced Functions
33
Scrolls the message forward.
Scrolls the message backward.
ENTER
Shows the next message or the idle
screen.
Short messages can be received from clients like Microsoft Messenger,
etc.
Message Waiting Indication (MWI)
If you did not answer a call and the mailbox recorded a message for
you, the idle screen shows that a recorded message is waiting for you.