All of a sudden we started having a problem with one of our new clients. They can receive email from accounts on our server, but anything off our server gets bounced back with a 'Relaying Denied' message. Disabling POP Before SMTP fixes the problem, but the strange thing is it's be enabled for over a year now without any problems. Nothing has been changed on our server recently, and a reboot didn't fix the problem. Any suggestions?