I have this FQL:
$femail = $facebook->api(array( \'method\' => \'fql.query\', \'locale\' => \'en_US\', \'query\' => \'SELECT email FROM user
You can't get email addresses of friends. Each account must opt-in to sharing their email address with the application. Friends can't opt other friends in, which is a good thing.
Also, as @Barkermn01 mentioned, drop the AND uid = '.$friend_id.'