Make sure the -f switch matches the backend farm id in the Relay Server configuration and the backend farm is enabled and the backend_security is compatible with the -cr https parameter. Make sure the -id switch matches the backend server id in the backend server is enabled. Make sure the -t switch matches the backend server token in the Relay Server configuration. Make sure the MAC address matches the backend server MAC in the Relay Server configuration. Also make sure the same authentication information is not shared by another instance of the Outbound Enabler.