The SIP voice mail button should always show the number of messages that the user has on the tooltip hover. When I had 3 messages it showed "Voice Mail" as the hover. When I had no new messages, it showed "Voice Mail" as the hover.
This issue is due new Jain-SIP Version.
I'll update my Jain-SIP code and fix inside SIP.
Or use some kind of Hack in Properties.
New JAIN-SIP Proporties updated to accept Voice Mail NOTIFY.
Add new property values to accept voice Mail NOTIFY in new JAIN-SIP API.