I've been evaluating the wwIPStuff utilities from West Wind. Specifically, to send email via SMTP. Everything was working great during the testing phase and I had decided that we were ready to register copies for production use when we encountered a problem. Sending emails inside of our domain works, but regardless of which, any email we send to outside of our domain results in the following SMTP error

550 5.7.1 Unable to relay for "email address"

Can you give me any insite as to the problem here?