Are there better instructions for the gateway setup in Smartermail?

I just need to relay my outbound mail through a different location for the short term and was going to setup the free version as an outbound gateway. Inbound mail will continue to come directly into the main mailserver. The instructions on this are somewhat vague. 

When instructed to login for settings, it isn't always clear WHICH box to login to. I have it has basically this.

On MAIN Smartermail server, add outbound gateway. Enter remote gateway URL and port. Enter login auth, if needed. Check to enable gateway mode if the remote gateway server is another Smartermail server.  Well it is but it isn't being used as a mailsever, just a gateway. So should this be on or off? If on does it need a user account for auth or the mailserver admin account?

On the box to be configured as the gateway/relay. In security, whitelist IP of MAIN smartermail server to allow SMTP bypass.