问题c_smtp_client.php
<?php
/* smtp client class */
class c_smtp_client
{
    var $connection;
    var $server;
    var $elog_fp;
    var $log_file='./smtp_client.log';
    var $do_log=true;
    var $need_auth=true;
    var $username;
    var $password;

    // 构造器
    function c_smtp_client($server='')
    {
        if (!$server)
        {
            $this->server="localhost";
        }
        else
        {
            $this->server=$server;
        }

        $this->connection = fsockopen($this->server, 25);
        if ($this->connection <= 0) return 0;
        fputs($this->connection,"HELO xyz\r\n");
    }
    
    function email($from_mail, $to_mail, $to_name, $header, $subject, $body)
    {
        if ($this->connection <= 0) return 0;
        
        // 邮件用户认证
        if ($this->need_auth)
        {
            $this->elog("AUTH LOGIN", 1);
            fputs($this->connection,"AUTH LOGIN\r\n");
            $this->elog(fgets($this->connection, 1024));
             
            $base64_username=base64_encode($this->username);
            $this->elog("$base64_username", 1);
            fputs($this->connection,"$base64_username\r\n");
            $this->elog(fgets($this->connection, 1024));

            $base64_password=base64_encode($this->password);
            $this->elog("$base64_password", 1);
            fputs($this->connection,"$base64_password\r\n");
            $this->elog(fgets($this->connection, 1024));
        }

        $this->elog("MAIL FROM:$from_mail", 1);
        fputs($this->connection,"MAIL FROM:$from_mail\r\n");
        $this->elog(fgets($this->connection, 1024));
        
        $this->elog("RCPT TO:$to_mail", 1);
        fputs($this->connection, "RCPT TO:$to_mail\r\n");
        $this->elog(fgets($this->connection, 1024));
        
        $this->elog("DATA", 1);
        fputs($this->connection, "DATA\r\n");
        $this->elog(fgets($this->connection, 1024));

        $this->elog("Subject: $subject", 1);
        $this->elog("To: $to_name", 1);
        fputs($this->connection,"Subject: $subject\r\n");
        fputs($this->connection,"To: $to_name\r\n");

        if ($header)
        {
            $this->elog($header, 1);
            fputs($this->connection, "$header\r\n");
        }

        $this->elog("", 1);
        $this->elog($body, 1);
        $this->elog(".", 1);
        fputs($this->connection,"\r\n");
        fputs($this->connection,"$body \r\n");
        fputs($this->connection,".\r\n");
        $this->elog(fgets($this->connection, 1024));

        return 1;
    }


    function send()
    {
        if ($this->connection)
        {
            fputs($this->connection, "QUIT\r\n");
            fclose($this->connection);
            $this->connection=0;
        }
    }

    function close()
    {
        $this->send();
    }

    function elog($text, $mode=0)
    {
        if (!$this->do_log) return;

        // open file
        if (!$this->elog_fp)
        {
            if (!($this->elog_fp=fopen($this->log_file, 'a'))) return;
            fwrite($this->elog_fp, "\n-------------------------------------------\n");
            fwrite($this->elog_fp, " Sent " . date("Y-m-d H:i:s") . "\n");
            fwrite($this->elog_fp, "-------------------------------------------\n");
        }

        // write to log
        if (!$mode)
        {
            fwrite($this->elog_fp, "    $text\n");
        }
        else
        {
            fwrite($this->elog_fp, "$text\n");
        }
    }
}
?>



c_mail.php
<?php

    /* 邮件发送类 */
    require_once dirname(__FILE__)."/c_smtp_client.php";
    static $c_smtp_client;
    if(!isset($c_smtp_client))
    {
        $c_smtp_client              =    & new c_smtp_client($smtp_server['name']);
        $c_smtp_client->do_log      =    false;
        $c_smtp_client->need_auth   =    $smtp_server['need_auth'];
        $c_smtp_client->username    =    $smtp_server['username'];
        $c_smtp_client->password    =    $smtp_server['password'];    
    }

    class c_mail
    {
        // html格式的Mail信笺
        function html_mailer($from_name,$from_mail,$to_name,$to_mail,$subject,$message,$reply_mail)
        {
            $headers     =    "";
            $headers    .=    "MIME-Version: 1.0\r\n";
            $headers    .=    "Content-type: text/html; charset=gb2312\r\n";
            $headers    .=    "From: ".$from_name."<".$from_mail.">\r\n";
            $headers    .=    "To: ".$to_name."<".$to_mail.">\r\n";
            $headers    .=    "Reply-To: ".$from_name."<".$reply_mail.">\r\n";
            $headers    .=    "X-Priority: 1\r\n";
            $headers    .=    "X-MSMail-Priority: High\r\n";
            $headers    .=    "X-Mailer: WebCMS MAIL SERV";

            // 开始发送邮件
            if($smtp_server['name']=='')
            {
                mail($to_mail, $subject, $message, $headers);
            }
            else
            {
                $c_smtp_client->email($from_mail,$to_mail,$to_name,$headers,$subject,$message);
                $c_smtp_client->send();        
            }
        }
}
?>


config.inc.php
<?php
    //smtp_server['name']=='';则表示直接使用mail();          
    //smtp_server['name']=='localhost';表示程序所在主机的smtp服务器
    $smtp_server['name']            =    "";
    $smtp_server['need_auth']       =    true;
    $smtp_server['username']        =    '';
    $smtp_server['password']        =    '';
?>


sendmail.php
<?php
    //调用方法
    require_once dirname(__FILE__)."/config.inc.php";
    require_once dirname(__FILE__)."/c_mail.php";
    $c_mail    = new c_mail();
    $c_mail->html_mailer($from_name,$from_mail,$to_name,$to_mail,$subject,$message,$reply_mail);

?>