function users_admin_enviar_mail_a_user($user, $subject, $body){
$respmail = leer_preferencia('site_mail_dir', ['cuenta'=>'samples', 'dominio'=>'example.com']);
$self = $respmail['cuenta'].'@'.$respmail['dominio'];
$from = 'From: '.$self."\n".
'Reply-To: '.$self."\n".
'X-Mailer: PHP/'.phpversion();
mail($user['mail'], $subject, $body, $from);
}