Your Exchange server should have SMTP enabled (on port 25 or 587). Most email servers either accept mail based on the source IP address (i.e. if it's coming from the local network then it's okay to relay) or by a login and password. If it's just by IP address all you need to do is configure the GRA to use that IP address and port. If it's by login and password you'll need to specify those as well. You can go through the initial setup or edit the
Web.config file manually to make the necessary changes (let me know if you need help with that).