public function multisend($template_name, $emails, $vars = [ ], $evars = [ ], $options = [ ]) {
        $post['template'] = $template_name;
        $post['email'] = is_array($emails) ? implode(',', $emails) : $emails;
        $post['vars'] = $vars;
        $post['evars'] = $evars;
        $post['options'] = $options;
        $result = $this->apiPost('send', $post);
        return $result;
    }