[otrs] Sending email in OTRS

Hopefully I'm posting to the right place.....bear with me as a noob. I just installed the latest version of otrs for Windows, running on windows 2000 server. I have successfully configured an Active Directory account with an exchange mailbox, and otrs is pulling the test mails I've sent via POP3 just fine. However, I can't sent email back out from OTRS. I have the 'check mx record' option disabled, and have also tried it enabled, and pointing to our internal DNS server. The POP3 virtual server on our Exchange machine isn't running, but I still can get mail into OTRS via POP3. What am I missing here?