I have been looking around...and I'm still looking for an answer on how you activate the requirement for smtp authentication from the users.
Unless someone has a better answer to this application. What I am trying to do is allow my users, some from other parts of the world, use sendmail. The problem I run into is that the spam control. I try to send a piece of email using my Outlook Express, using my account from the server, then I get a spam control error saying that the domain is rejected.
Any ideas out there? I'm not too sure what the best course of action is...except to disable the spam control, and make smtp authentication active.