I've built a web page in php that sends emails to an exchange server. I get the following error message for some email addresses, but not all addresses. Warning: mail() [function.mail]: SMTP server response: 550 <example@address.com>: Recipient address rejected: User unknown in local recipient table The email addresses that get rejected all belong to the company that I built the web page for. However some of the addresses that belong to the company work e.g. info@company.com works but reception@company.com doesn't Could someone please tell mewhatI cando to solve the problem. Also, what exactly is the local recipient table? Any help greatly appreciated.