Hi there, I'm new to the forum and am seeking help with an on going issue that has plagued my company's e-mail server for way too long. We're currently victim of a Taiwanese hacker group that is using our server to relay spam e-mail. Up until a few weeks ago I had no idea how to prevent them from using our server for relay and still keep my users able to e-mail from their company e-mail addresses. The day before last I started changing the configuration on the server to require a username and password for outbound messages using basic authentication. I created a user, applied the password, and configured outlook correctly. When I tried to e-mail a message using outlook I received a 550 cannot relay for such and so. Worse yet is all my users are getting a 550 cannot relay. What can I do to let all my users e-mail from home and not have the spammers muck up my server?