Multiple sites multiple relays

Hi, I’ve got 2 sites, let’s call it siteA and siteB both with a domino server connected via VPN. SiteA is the primary site and is currrently the relay host for siteB i.e. messages for notes mailboxes as well as messages to the internet are all routed through siteA and it’s mail gateway. I am trying to set up a seperate internet mail gateway for SiteB in which only mail bound for the internet should be routed. Mail for SiteA should still be routed directly to SiteA’s domino server. Will I only need to edit the “Relay host for msgs leaving the local internet domain” field for the router/smtp? Currently this is set to point to SiteA’s domino server.

Any advise will be great. Thanks!