Internal Relay -> Dreamhost SMARTHOST

I need to use an internal IIS 6.0 Relay on Server 2008, and want to use my Dreamhost-based SMTP server. So far I have been able to relay using GMAIL’s SMART HOST with this IIS 6.0 relay, but no matter what settings I try, I am UNABLE to send messages.

What are the proper settings for an IIS 6.0 based relay to relay through Dreamhost’s servers. I’ve tried changing ports to 587 and enabling TLS, I’ve tried setting Anonymous (works, but obviously only to internal email accounts), and nothing seems to work.