For subscribers to access their mailbox, one or more subscriber access numbers must be specified in the dial plan. This should be the pilot number for the PBX hunt group that the subscribers will use.
To associate a subscriber access extension to the dial plan, execute the following steps:
1. Launch the Exchange Management Console.
2. Under the Organization Configuration folder, select the Unified Messaging container.
3. Select the UM Dial Plan tab.
4. Select the dial plan in the results pane, such as SFO Dial Plan.
5. In the Action menu, select Properties.
6. Select the Subscriber Access tab.
7. Enter the extension that subscribers will use to access their mailboxes, such as 333.
8. Click Add.
9. Click ...