I provide free web based e-mail access to the users of my server. This is done in 2 ways, the one that my users have access to is a PHP based interface for my sendmail server. Anyways, I recently got an e-mail from somebody at hotmail claiming that I was spamming them and that it had to cease or I would be sued. I don't think she was really going to sue me, and if she did she probably wouldn't get much money. But I just wanted to ask if anybody here had any ideas on how to stop spammers from using my server, I don't know how to see who it is. I wasn't using authentication before as users were actually users of my free web hosting service, and were required to login for that, so I didn't make them login in or anything for the PHP based web mail. Anyways, I know that I won't be able to figure out who the spammers were, but I was wondering if anybody could help me find some options to keep spammers from using my server. Thanks and bye.