scripts/adduser.inc.php

find:
PHP Code

$xml_string = @file_get_contents("http://www.stopforumspam.com/api?email=". $Email);

replace:
PHP Code

$xml_string = @file_get_contents("http://www.stopforumspam.com/api?email=". $Email . "&ip=" . find_environmental('REMOTE_ADDR'));