In Symantec Messaging Gateway (SMG) it is possible to configure Directory Data Sources (such as LDAP) to perform certain operations such as recipients validation, address resolution, authentication and routing.

SMG also offers a setting called "Enable Distribution Expansion" which allows Distribution Lists to be 'expanded' when performing address validation.

This function does not support Directtory Data Sources configured for routing.

The appliance is currently working as per its design and the Distribution Expansion only supports Address Resolution.