[otrs] Directing Mail to server

Is there any way to direct the system to use a mail relay for sending e-mail instead of relying on the MTA in the system? I ask because we have the OTRS system setup inside our network behind our firewall and several of our e-mails get blocked when we send to our sister domains. The Spam filter cannot resolve the DNS name of our internal server because we do not point it to our internal DNS servers for resolution. Therefore, it does not the find a valid pointer to the OTRS server and blocks the mail as Spam. Bakari A. Allen Director of Information Technology Jackson and Hardwick, LLC 770.625.0200 extension 210 bakari.allen@jhlaw.net