mail() issue

Hello All, I am having an issue with mail. include '../../Process/include/LDAP.php'; echo $user_email; $to = $user_email; $subject = 'Request Submitted Successfully!'; $message = "Congratulations!\nYour request has been successfully submitted.\nThis is an automated email, please do not reply."; mail($to, $subject, $message); In the include file I am querying Active Directory and pulling the email address for the current user and assigning it to the $user_email variable. (This works fine) Then for a sanity check I am echoing out the retrieved value. (Displays the correct alue) Then, I am assigning the values for my message variables and generating the mail() message. As far as I can tell everything "looks" okay, however when I run my script I get the following error: PHP Warning: mail() [function.mail<http://develop1/credit%20card%20processing/Submit/ChildSupport/function.mail>]: SMTP server response: 504 <br />: Recipient address rejected: need fully-qualified address. The value of $user_email when it is echoed out above is user@domain.com. Any ideas?