Whether you are allowed to "forward" mail from your email server to another email server is up to the your server admin. Some systems/policies allow it and others don't. Check with your Exchange admin to see if you can forward your Exchange mail. This action is sometimes handled only by the Exchange admin upon your request. Just depends. Or, if webmail, ... just poke around to see if you can find that option.Can I send my Exchange account mail there?
I would try it as primary if that's possible.