Sooo, in the E-mail gateway section in the voicemail, you should have SMTP selected for the E-Mail System, your mail server programmed for yer SMTP server, Voice Mail as yer Real Name and
[email protected] as the username. If you are trying to use Unified Messaging, the individual mailboxes need to have that enabled, and the client s/w installed.
If that doesn't work, try to telnet to yer mail server from the voicemail server on port 25. If you can successfully connect, then SMTP is running on yer mail server. If you cannot send mail in this fashion (you will need to Google 'SMTP telnet commands' if you don't know them), then likely SMTP is not running or you are running Secure SMTP. In that case you will need to setup a voicemail account on yer mail server like any other user, then program yer e-mail gateway w/ those settings.