Drupal6 hook_mail实现发送HTML邮件

/*
 * 实现hook_mail
 * $key 用于区分邮件操作
 * $message 邮件内容
 * $params 参数，如果有的话...
 * 调用方法：drupal_mail('example', 'html', 'example@gmail.com', language_default(), array('subject' => '', 'body' => ''))
 */
function example_mail($key, &$message, $params) {
    switch($key) {
        case 'html':
            $message['subject'] = $params['subject'];
            $message['body'][] = $params['body'];
            $message['headers'] = array(
                'MIME-Version' => '1.0',
                'Content-Type' => 'text/html; charset=UTF-8; format=flowed',
                'Content-Transfer-Encoding' => '8Bit',
                'X-Mailer' => 'Drupal',
                'From' => isset($params['from']) ? $params['from'] : variable_get('site_name', 'Infinity')
            );
            break;
    }
}