以前评论回复邮件提醒通知功能是通过“Comment Reply Notification”插件来实现的，今天查看大发主题代码时发现以下代码，把以下代码直接插入主题function.php文件既可，简单明了，并且显示样版还不错。看到是由大神willin kan贡献的，可惜他老人家不玩WordPress了，于是公布此段代码给大家。

具体邮件提醒通知效果如下：

// comment_mail_notify v1.0 by willin kan. (所有回覆都發郵件)
function comment_mail_notify($comment_id) {
    $comment = get_comment($comment_id);
    $parent_id = $comment->comment_parent ? $comment->comment_parent : '';
    $spam_confirmed = $comment->comment_approved;
    if (($parent_id != '') && ($spam_confirmed != 'spam')) {
        $wp_email = 'no-reply@' . preg_replace('#^www\.#', '', strtolower($_SERVER['SERVER_NAME'])); //e-mail 發出點, no-reply 可改為可用的 e-mail.
        $to = trim(get_comment($parent_id)->comment_author_email);
        $subject = '你在 [' . get_option("blogname") . '] 的留言有了新回复';
        $message = '

    <div id="newsletter" style="background: none repeat scroll 0 0 #F1F8FD; color: #333333; font: 13px/20px "Helvetica Neue",Helvetica,Arial,Sans-serif;font-family:"Hiragino Sans GB","Microsoft YaHei","Helvetica Neue",Helvetica,Arial,sans-serif!important;">
    <div class="wrapper" style="margin: 20px auto 0; width: 500px; padding-top:16px; padding-bottom:10px;">
    <div class="header clearfix">
<a class="logo" style="float:left">
<img src="'.get_template_directory_uri().'/img/logo.png">
</a>
</div>
<br style="clear:both; height:0">
<div class="content" style="background: none repeat scroll 0 0 #FFFFFF; border: 1px solid #E9E9E9; margin: 2px 0 0; padding: 30px;">
    <p><strong>' . trim(get_comment($parent_id)->comment_author) . ', 你好!</strong></p>
    <p class="message" style="border-top: 1px solid #DDDDDD;margin: 15px 0 15px;padding: 15px;"><strong>您曾在《' . get_the_title($comment->comment_post_ID) . '》的留言为:</strong><br />'
            . trim(get_comment($parent_id)->comment_content) . '</p>
    <p class="message" style="border-top: 1px solid #DDDDDD;margin: 15px 0 15px;padding: 15px;"><strong>' . trim($comment->comment_author) . ' 给你的回复是:</strong><br />'
            . trim($comment->comment_content) . '<br /></p>
    <p class="footer" style="border-top: 1px solid #DDDDDD; padding-top:6px; margin-top:15px; color:#838383;">你可以点击此链接 <a href="' . htmlspecialchars(get_comment_link($parent_id)) . '">查看完整内容</a> | 欢迎再次来访<a href="' . home_url() . '">' . get_option('blogname') . '</a></p>
    </div></div></div>';

        $from = "From: \"" . get_option('blogname') . "\" <$wp_email>";
        $headers = "$from\nContent-Type: text/html; charset=" . get_option('blog_charset') . "\n";
        wp_mail( $to, $subject, $message, $headers );
    }
}
add_action('comment_post', 'comment_mail_notify');

提醒，以上代码logo.png路径请根据真实修改。

更新（2014-06-26）： 更新邮件内容样式，具体效果请看下图。

更新后的完整代码如下，使用方法上面一样的：

// comment_mail_notify v1.0 by willin kan. (所有回覆都發郵件)
function comment_mail_notify($comment_id) {
    $comment = get_comment($comment_id);
    $parent_id = $comment->comment_parent ? $comment->comment_parent : '';
    $spam_confirmed = $comment->comment_approved;
    if (($parent_id != '') && ($spam_confirmed != 'spam')) {
        $wp_email = 'no-reply@' . preg_replace('#^www\.#', '', strtolower($_SERVER['SERVER_NAME'])); //e-mail 發出點, no-reply 可改為可用的 e-mail.
        $to = trim(get_comment($parent_id)->comment_author_email);
        $subject = '你在 [' . get_option("blogname") . '] 的留言有了新回复';
        $message = '

<div align="center" style="PADDING-BOTTOM: 66px; BACKGROUND-COLOR: #ededed; PADDING-LEFT: 0px; WIDTH: 100%; PADDING-RIGHT: 0px; COLOR: #777; PADDING-TOP: 66px">
<div style="TEXT-ALIGN: left; BACKGROUND-COLOR: #fff; WIDTH: 700px">
<h1 style="TEXT-ALIGN: center; PADDING-BOTTOM: 54px; MARGIN: 0px auto; MIN-HEIGHT: 30px; PADDING-LEFT: 0px; PADDING-RIGHT: 0px; PADDING-TOP: 56px">
<img src="'.get_template_directory_uri().'/img/logo.png">
</h1>
<div style="BACKGROUND-COLOR: #444; MARGIN: 0px 60px 30px; WIDTH: 580px; HEIGHT: 4px"></div>
<h2 style="LINE-HEIGHT: 50px; MARGIN: 0px 60px 30px; WIDTH: 580px; COLOR: #24b0cf; FONT-SIZE: 28px; FONT-WEIGHT: bold">
<p class="MsoNormal" align="center" style="TEXT-ALIGN: center">
<b>
<span style="FONT-FAMILY: 微软雅黑; FONT-SIZE: 15pt">
<font size="5">
<font color="black">'.$subject.'
</font>
</font>
</span>
</b>
</p>
</h2>
<div style="BACKGROUND-COLOR: #444; MARGIN: 0px 60px 40px; WIDTH: 580px; HEIGHT: 1px"></div>
<div style="MARGIN: 0px 60px 30px; WIDTH: 580px;">
<p><strong>' . trim(get_comment($parent_id)->comment_author) . ', 你好!</strong></p>
<p class="message"><strong>您曾在《' . get_the_title($comment->comment_post_ID) . '》的留言为:</strong><br />'
            . trim(get_comment($parent_id)->comment_content) . '</p>
<p><strong>' . trim($comment->comment_author) . ' 给你的回复是:</strong><br />'
            . trim($comment->comment_content) . '<br /></p>
<p>你可以点击此链接 <a href="' . htmlspecialchars(get_comment_link($parent_id)) . '">查看完整内容</a> | 欢迎再次来访<a href="' . home_url() . '">' . get_option('blogname') . '</a></p></div><div style="BORDER-BOTTOM: #a5a5a5 2px dashed; MARGIN: 40px auto 30px; WIDTH: 700px"></div><table style="PADDING-BOTTOM: 30px; MARGIN: 0px 60px 30px; PADDING-LEFT: 0px; WIDTH: 580px; PADDING-RIGHT: 0px; PADDING-TOP: 0px">
<tbody>
<tr><td style="WIDTH: 500px">
<p><span style="PADDING-BOTTOM: 2px; BACKGROUND-COLOR: #24b0cf; PADDING-LEFT: 12px; PADDING-RIGHT: 12px; COLOR: #fff; FONT-SIZE: 12px; FONT-WEIGHT: bold; PADDING-TOP: 2px">QQ：1556178</span></p>
<p style="LINE-HEIGHT: 20px; MARGIN: 0px; COLOR: #999; FONT-SIZE: 12px">©' . get_option('blogname') . ' 2014</p>
<p style="LINE-HEIGHT: 20px; MARGIN: 0px; COLOR: #999; FONT-SIZE: 12px">' . get_bloginfo( 'description' ) .'</p>
<br>
</td></tr>
</tbody>
</table></div>
</div>';