The script stalls on the set_socket_blocking function, if the function is commented out or removed the script works perfectly in php 4.0 Beta 2. This script works entirely in
php 3.0.8 versions an higher.

$fp = fsockopen ( $mail_server, 25 );  
if ($fp) { 
    set_socket_blocking ( $fp, false ); 
    echo "works";
    fputs ( $fp, "QUIT\n" ); 
}