html格式邮件垃圾率过高的处理办法

原先的邮件采用Content-Type: text/html

下面是X-Spam的得分情况，当 score 超过6分就被当作垃圾邮件处理了

X-Spam-Status: Yes, score=6.3 required=6.0 tests=CONTENT_TYPE_PRESENT,
    DIRECTUNKNOWN,HTML_MESSAGE,MIME_HTML_ONLY,ONLY1HOPDIRECT,RDNS_NONE,
    TO_NO_BRKTS_FROM_MSSP,TO_NO_BRKTS_NORDNS_HTML,URIBL_BLOCKED,UTF8 autolearn=no
    version=3.3.1
X-Spam-Report:
    *  0.0 URIBL_BLOCKED ADMINISTRATOR NOTICE: The query to URIBL was blocked.
    *       See http://wiki.apache.org/spamassassin/DnsBlocklists#dnsbl-block
    *      for more information.
    *      [URIs: handbook.jp]
    * -0.1 CONTENT_TYPE_PRESENT exists:Content-Type
    *  0.3 DIRECTUNKNOWN directly received spam from suspicious dynamic IP
    *  1.0 ONLY1HOPDIRECT ONLY1HOPDIRECT
    *  1.0 HTML_MESSAGE BODY: HTML included in message
    *  0.4 MIME_HTML_ONLY BODY: Message only has text/html MIME parts
    * -0.1 UTF8 RAW: UTF-8 message body
    *  1.3 RDNS_NONE Delivered to internal network by a host with no rDNS
    *  2.5 TO_NO_BRKTS_FROM_MSSP Multiple formatting errors
    *  0.0 TO_NO_BRKTS_NORDNS_HTML To: misformatted and no rDNS and HTML only

解决办法就是采用Content-Type: multipart/alternative

这种类型可以同时发送两种类型的邮件 text/plain 和 text/html， 大大降低邮件的 score

下面是采用multipart/alternative 这种类型的得分情况 因为低于6分 没有X-Spam-Report

X-Spam-Status: No, score=3.5 required=6.0 tests=CONTENT_TYPE_PRESENT,
    DIRECTUNKNOWN,HTML_MESSAGE,MULTIPART_ALTERNATIVE,ONLY1HOPDIRECT,RDNS_NONE,
    URIBL_BLOCKED,UTF8 autolearn=no version=3.3.1

下面是具体代码

function sendAlternativeMail($to, $from, $subject, $plainmessage, $htmlmessage, $bcc = null, $cc = null) {
    $to   = base64($to);
    $from = base64($from);
    $subject = ‘=?UTF-8?B?‘ . base64_encode($subject) . ‘?=‘;
    $boundary = uniqid(‘np‘);
　　 //set header
    $headers = "MIME-Version: 1.0\r\n";
    $headers .= "From: ".$from."\r\n";
    $cc && $headers .= "Cc: $cc\n";
    $bcc && $headers .= "Bcc: $bcc\n";
    $headers .= "Content-Type: multipart/alternative;boundary=" . $boundary . "\r\n";
　　 //set plain body
    $message = "\r\n\r\n--" . $boundary . "\r\n";
    $message .= "Content-type: text/plain;charset=utf-8\r\n\r\n";
    $message .= $plainmessage;
　　 //set html body
    $message .= "\r\n\r\n--" . $boundary . "\r\n";
    $message .= "Content-type: text/html;charset=utf-8\r\n\r\n";
    $message .= $htmlmessage;
    //end
    $message .= "\r\n\r\n--" . $boundary . "--";

    return mail($to, $subject, $message, $headers);
}
//encode email address
function base64($string){
    if (!$string) {
        return null;
    }
    $array = explode(‘,‘, $string);
    foreach ($array as &$a) {
        $a = trim($a);
        if (preg_match(‘/(.*)(<[^>][email protected][^>]+>)$/U‘, $a, $match)) {
            $a = ‘=?UTF-8?B?‘ . base64_encode($match[1]) . ‘?=‘ . $match[2];
        }
    }
    return implode(‘,‘, $array);
}

参考资料：http://krijnhoetmer.nl/stuff/php/html-plain-text-mail/