mail command failing

Hi all, I'm very puzzled by this. I've been using the php mail command for years but now I can't get it to work and can't figure out how to diagnose the problem. The code below was copied from the manual (addresses changed, etc); php.ini has safe_mode off; binary is at /usr/sbin/sendmail. <?php ini_set("SMTP","localhost" ); ini_set('sendmail_from', 'mike.wright@mailinator.com'); $name = "Mike Wright"; //senders name $email = "mike.wright@mailinator.com"; //senders e-mail adress $recipient = "mike.wright@mailinator.com"; //recipient $body = "The text for the mail..."; //mail body $subject = "Subject for review"; //subject $header = "From: $name <$email>\r\n"; //optional headerfields $echo = mail($recipient, $subject, $body, $header) ? 'success':'fail'; echo "<br/><br/>$echo"; I can access the mail server with "/usr/bin/mailx" and by telnet "localhost 25". I can also send mail using php by using 'exec (" echo $body | mailx -s $subject $recipient")'. php-5.2.29 on fedora10 with apache 2.2.14. Can this be selinux related? Any ideas or troubleshooting tips? Thanks, Mike Wright