Dreamhost with Exchange 2003

My ISP blocks port 25. I’d like to use MS Exchange for one of my domains on a local server. I know that DH’s servers will relay on port 587 which would get around this issue. Does anyone out there currently utilize DH SMTP servers as a relay, and how did they configure exchange for this? I know it has to be authenticated relay, but my smarthost doesn’t work and I expect its the way I have the authentication configured.

Thanks in advance