Solution
The SMTP service has two states. The standard state of the service enables local delivery. The routing state will forward all incoming sessions to the routed destination. To enable the routing state of the SMTP service perform the following configuration steps:
1. Log into the webadmin interface.
2. Go to the "Clustering" context and select "Clustering Setup" from the list.
3. On the "Routing and Authentication" tab, go to the "Routing" section.
4. Select the "Enable SMTP routing" check-box.
5. Select the user map from the drop-down list. The SMTP service will use this map to perform the information lookup.
6. Click the "Save Configuration" button to make the changes permanent.
WARNING: While the routing state is active, local delivery to the server storage is disabled and no messages will be delivered locally, even if the destination domain exists and is configured properly.