Email relay for one internal domain, but not for another

One of our email domains has been set up to use outlook.com, but we have another which does not.  We want to relay all emails for domain_1.com to go through the outlook.com server (I’ve tested, it works), but our domain_2.com we do not want to relay – we want it to connect directly to the specified recipient server.

Is there a way to do that through the IceWarp software?