Can Zimbra be configured to be a smarthost and relay mail for a domain ?

I have a Zimbra server that is setup and working great, but have a coworker that is doing his Microsoft Exchange cert and he would like to have a domain that can forward mail to his dynamic ip (which will have exchange listening on)

so is there a way to tell zimbra that it will be relaying mail for domain abz.com to host.dynamicip.com ?