I have a windows 2003 SMTP server running on a DMZ. I use it to send the incoming mail to my Exchange server 2003 running on my lan. I need to be able to authenticate with my email account so I can relay email from an outside connection, otherwise I get error 550. I need to know what ports I need to open on the firewall and how to set it up. It is any other more secure way to have this working?