SBS 2003 Exchange – Can’t e-mail to pop3 users on same domain.

I am unable to send emails to users on the same email domain, but not our local domain. They access their email via pop3 at remote locations. At first it would just reject the email as unknown user, so I added them as a user (even though they won’t login) Basiclly, I want to know if I can manually add an address and force it to be sent out via SMTP so exchange doesn’t try to keep it in house. Any suggestions?