这是使用PHP发送电子邮件的正确方法吗？

我有点担心这个函数是否以应有的方式发送可以在大多数电子邮件和Web邮件客户端上正确识别的电子邮件，特别是我最关心的是这种疑问：

• UTF-8 声明和附件的格式是否正确？
• 我需要使用 quoted_printable_decode（） 吗？如果是，在哪里？
• 内容传输编码：7 位还是 8 位？我总是看到7，但由于我正在发送UTF-8编码的邮件，我不确定。
• 我应该使用mb_send_mail（）还是mail（）就足够了？

编辑：我不知道为什么，但代码没有正确显示，我让它可用@http://gist.github.com/104818

编辑2：我知道电子邮件处理的其他替代方案（库），但为了我自己的好奇心和知识，我只想知道这段代码是否是100%好的，或者它是否是错误的。

function Email($name, $from, $to, $subject, $message, $bcc = null, $attachments = null)
{
    ini_set('SMTP', 'localhost');
    ini_set('sendmail_from', $from);

    $name = filter_var($name, FILTER_SANITIZE_STRING);
    $from = filter_var($from, FILTER_SANITIZE_EMAIL);
    $subject = filter_var($subject, FILTER_SANITIZE_STRING);

    $boundary = '_Boundary_' . md5(microtime(true) . mt_rand(0, PHP_INT_MAX));

    $headers = array
    (
        'MIME-Version: 1.0',
        'Content-Type: multipart/mixed; boundary="Mixed' . $boundary . '"',
        'Date: ' . date('r', time()),
        'From: "' . $name . '" <' . $from . '>',
        'Reply-To: "' . $name . '" <' . $from . '>',
        'Return-Path: "' . $name . '" <' . $from . '>',
        'X-Mailer: PHP ' . phpversion(),
        'X-Priority: 2',
        'X-MSMail-Priority: High',
        'X-Originating-IP: ' . $_SERVER['SERVER_ADDR'],
    );

    if (is_null($to) === false)
    {
        if (is_array($to) === false)
        {
            $to = explode(',', $to);
        }

        foreach ($to as $key => $value)
        {
            $to[$key] = filter_var($value, FILTER_SANITIZE_EMAIL);
        }

        $to = implode(', ', array_filter($to));
    }

    if (is_null($bcc) === false)
    {
        if (is_array($bcc) === false)
        {
            $bcc = explode(',', $bcc);
        }

        foreach ($bcc as $key => $value)
        {
            $bcc[$key] = filter_var($value, FILTER_SANITIZE_EMAIL);
        }

        $headers[] = 'BCC: ' . implode(', ', array_filter($bcc));
    }

    if (is_null($attachments) === false)
    {
        settype($attachments, 'array');

        foreach ($attachments as $key => $value)
        {
            if (is_file($value) === true)
            {
                $attachments[$key] = array
                (
                    '',
                    '--Mixed' . $boundary,
                    'Content-Type: application/octet-stream; name="' . basename($value) . '"',
                    'Content-Disposition: attachment; filename="' . basename($value) . '"',
                    'Content-Transfer-Encoding: base64',
                    '',
                    trim(chunk_split(base64_encode(file_get_contents($value)))),
                );

                $attachments[$key] = implode("\n", $attachments[$key]);
            }

            else
            {
                unset($attachments[$key]);
            }
        }

        $attachments = implode("\n", $attachments) . "\n";
    }

    $message = array
    (
        'This is a multi-part message in MIME format.',
        '',
        '--Mixed' . $boundary,
        'Content-Type: multipart/alternative; boundary="Alt' . $boundary . '"',
        '',
        '--Alt' . $boundary,
        'Content-Type: text/plain; charset="UTF-8"',
        'Content-Disposition: inline',
        'Content-Transfer-Encoding: 8bit',
        '',
        trim(strip_tags($message, '<a>')),
        '',
        '--Alt' . $boundary,
        'Content-Type: text/html; charset="UTF-8"',
        'Content-Disposition: inline',
        'Content-Transfer-Encoding: 8bit',
        '',
        trim($message),
        '',
        '--Alt' . $boundary . '--',
        $attachments,
        '--Mixed' . $boundary . '--',
    );

    if (@mail($to, stripslashes($subject), implode("\n", $message), implode("\n", $headers)) === true)
    {
        return true;
    }

    return false;
}