I recently had to figure out a way as a voicemail came in as our e-mail server was in the middle of a reboot.
Backup the Unit, if you look in the Contacts\Ext\Msgs folder, there are bunch of cabs. They should be able to be opened by any Archive program (I use 7-zip) and you can pull the WAV file, and therefore, forward the message.
It's not pretty, but under the circumstances, was the best I had available.
Still doesn't substitute the "press 8 to forward"...