DO you have in your Enterprise Parameters the URL using thr FQDN of the CCM or the IP address? Switch to IP address to rule out DNS, also try a IISRESET from the command line of the server where the directory is homed too.

What Regions do you have configured on your call manager? Are you using G711 or g729 between those calling parties? If you are that is why, you need a transcoder.

Good advice.Ive done this scenario many times with customers. The best and easiest way is to do a Dirt backup/Restore.

Also...You need to make sure that the packets are being routed properly. I think ther eis a deubgg ikcmp or whatever as well.

Two ways, but then your MWI isnt going to work since Unity scours the Inbox for new messages.Rules or Delivery restrictions on exchange/AD.