此方法初始目的来源于公司邮箱数据库里面有损坏的邮件，导致MAC版本客户端无法使用POP3协议拉取邮件。

原理为使用POP3协议的命令操作删除数据库内损坏的邮件列表，从而解决通过POP3协议拉取邮件时卡住不拉取邮件的问题。
方法采取脚本方式，使用PHP编写，下面是代码，贴出来共享。

使用方法：

• php fixmail.php username password

<?php
/*
* Fix mail by deleting corrupted mails.
* Use USER and PASS 
* POP3 protocol refer RFC1939 (http://tools.ietf.org/rfc/rfc1939.txt)
*/

$host = "邮箱服务器域名或IP";
$port = "110"; // secure port is 995

if ($argc != 3) {
    print "Usage: \n";
    print "\t" . $argv[0] . " user pass\n";
    print "\n";
    exit;
}

$username = $argv[1];
$password = $argv[2];


function sendQuery($socket, $CMD, $data = '')
{
    $data = trim($data);
    if (empty($data)) {
        $send = "$CMD\r\n";
    } else {
        $send = "$CMD $data\r\n";
    }

    socket_send($socket, $send, strlen($send), 0);
    return;
}

function getResult($socket, $CMD = '')
{
    $retBuffer = '';
    while(($len = @socket_recv($socket, $buffer, 1024, 0)) >0) {
        //print $buffer;
        //print "\n";
        $retBuffer .= $buffer;
        $n = strlen($retBuffer);
        if (($CMD == 'LIST' || $CMD == 'TOP' || $CMD == 'RETR' || $CMD == 'UIDL') && 
            ($retBuffer[0] == '+' && $retBuffer[1] == 'O' && $retBuffer[2] == 'K') &&
            ! ($retBuffer[$n-1] == "\n" && $retBuffer[$n-2] == "\r" && $retBuffer[$n-3] == '.')) {
            // POP3协议返回数据
            // 第一行为状态码 +OK 或者 -ERR
            // 若有数据，数据以 ".\r\n" 结束
            $buffer = '';
            continue;
        }
        break;
    }
    return $retBuffer;
}

function getConnection($host, $port)
{
    $socket = socket_create(AF_INET, SOCK_STREAM, SOL_TCP)
      or die("Unable to create socket\n");

    socket_connect($socket, $host, $port);
    $r = getResult($socket); // Get greeting info
    print $r;

    return $socket;
}

function getLoginSession($host, $port, $user, $pass)
{
    $socket = getConnection($host, $port);

    sendQuery($socket, 'USER', $user);
    $r = getResult($socket, 'USER');
    print $r;

    sendQuery($socket, 'PASS', $pass);
    $r = getResult($socket, 'PASS');
    print $r;

    return $socket;
}

function getMailIdList($socket) 
{
    sendQuery($socket, 'LIST');
    $r = getResult($socket, 'LIST');

    $lines = explode("\r\n", $r);
    $lines = array_filter($lines);
    $arrMailId = array();
    foreach($lines as $v) {
        if ($v[0] == '+' && $v[1] == 'O' && $v[2] == 'K') continue;
        if ($v[0] == '.') continue;
        $v = trim($v);
        if (empty($v)) continue;
        $mid = explode(' ', $v);
        //print "$v\n";
        $arrMailId[] = $mid[0];
    }
    return $arrMailId;
}

function checkMailCorrupt($socket, $mailId)
{
    sendQuery($socket, 'TOP', "$mailId 0");
    $r = getResult($socket, 'TOP');
    $r = trim($r);
    if ($r == '-ERR Message corrupted') {
        print "$mailId $r\n";
        return 1;
    } else if ($r[0] == '-' && $r[1] == 'E' && $r[2] == 'R' && $r[3] == 'R') {
        print "$mailId $r\n";
        return 2;
    }
    return 0;
}

function deleteMail($socket, $mailId)
{
    sendQuery($socket, 'DELE', "$mailId");
    $r = getResult($socket, 'DELE');
    print "DELE $mailId " . $r;
    return;
}

function quitAndClose(& $socket)
{
    sendQuery($socket, 'QUIT');
    $r = getResult($socket, 'QUIT');
    socket_close($socket);
    $socket = null;
    print $r;
    return;
}

// START
// get mail id list
$socket = getLoginSession($host, $port, $username, $password);
$arrMailId = getMailIdList($socket);
quitAndClose($socket);

$totalMail = count($arrMailId);
print "\nTotal mail count $totalMail\n\n";

// delete corrupt mail
// 删除之后id会重新补齐，所以从最大id开始
// 同一封邮件id在不同会话之间不一定相同, 但可以通过UIDL来获得邮件唯一ID标识
// 所以邮件客户端会先获取UIDL, 然后再获取LIST, 最后RETR获取邮件
$totalCorrupt = 0;
$cur = $totalMail - 1;
while ($cur >= 0) {
    $n = 6;
    $socket = getLoginSession($host, $port, $username, $password);
    while(($n > 0) && ($cur >= 0)) {
        $id = $arrMailId[$cur];
        $r = checkMailCorrupt($socket, $id);
        if ($r == 1) {
            $totalCorrupt ++;
            deleteMail($socket, $id);
            $n --;
        } else if ($r != 0) {
            $n --;
        }
        $cur --;
    }
    quitAndClose($socket);
}

print "\nTotal mail corrupt count $totalCorrupt\n\n";

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