This is experimental, as you can see when you are whisked away to the plugin download page.  If you're the adventurous type and you go for it, let me know what you think. 
  
Seems this only works with Netscape browsers at this time.  Internet Explorer 4.0 will appear to work but the email received does not contain the voice attachment. 
  
For more info from the creators click anywhere on the voice mail icon to go to their URL.  Although their FAQ's does not include Communicator I am using it just fine.