现在很多主机空间都是IIS上执行PHP程序，大多不能直接用mail()发送邮件，有了这个类只要你有注册过邮箱，就可以随意的发送邮件，速度也不慢哦。

//******************************
// smtp.php文件
//
//******************************
<?php
class smtp
{


    /* Public Variables */
    var $smtp_port;
    var $time_out;
    var $host_name;
    var $log_file;
    var $relay_host;
    var $debug;
    var $auth;
    var $user;
    var $pass;

    /* Private Variables */
    var $sock;

    /* Constractor */


    function smtp($relay_host = "", $smtp_port = 25,$auth = false,$user,$pass)
    {
        $this->debug = FALSE;
        $this->smtp_port = $smtp_port;
        $this->relay_host = $relay_host;
        $this->time_out = 30; //is used in fsockopen()
        
        #

        $this->auth = $auth;//auth
        $this->user = $user;
        $this->pass = $pass;
        
        #

        $this->host_name = "localhost"; //is used in HELO command
        $this->log_file = "";


        $this->sock = FALSE;


    }


    /* Main Function */


    function sendmail($to, $from, $subject = "", $body = "", $mailtype, $cc = "", $bcc = "", $additional_headers = "")
    {


        $mail_from = $this->get_address($this->strip_comment($from));
        $body = ereg_replace("(^ (\r\n))(\.)", "\1.\3", $body);
        $header = "MIME-Version:1.0\r\n";

        if($mailtype=="HTML"){
            $header .= "Content-Type:text/html\r\n";
        }

        $header .= "To: ".$to."\r\n";

        if ($cc != "") {
            $header .= "Cc: ".$cc."\r\n";
        }

        $header .= "From: $from<".$from.">\r\n";
        $header .= "Subject: ".$subject."\r\n";
        $header .= $additional_headers;
        $header .= "Date: ".date("r")."\r\n";
        $header .= "X-Mailer:By Redhat (PHP/".phpversion().")\r\n";

        list($msec, $sec) = explode(" ", microtime());

        $header .= "Message-ID: <".date("YmdHis", $sec).".".($msec*1000000).".".$mail_from.">\r\n";

        $TO = explode(",", $this->strip_comment($to));

        if ($cc != "") {
            $TO = array_merge($TO, explode(",", $this->strip_comment($cc)));
        }


        if ($bcc != "") {
            $TO = array_merge($TO, explode(",", $this->strip_comment($bcc)));
        }

        $sent = TRUE;

        foreach ($TO as $rcpt_to) {
            $rcpt_to = $this->get_address($rcpt_to);
            
            if (!$this->smtp_sockopen($rcpt_to)) {
                $this->log_write("Error: Cannot send email to ".$rcpt_to."\n");
                $sent = FALSE;
                continue;
            }

            if ($this->smtp_send($this->host_name, $mail_from, $rcpt_to, $header, $body)) {
                $this->log_write("E-mail has been sent to <".$rcpt_to.">\n");
            } else {
                $this->log_write("Error: Cannot send email to <".$rcpt_to.">\n");
                $sent = FALSE;
            }

            fclose($this->sock);

            $this->log_write("Disconnected from remote host\n");
        }

        return $sent;

    }





/* Private Functions */





    function smtp_send($helo, $from, $to, $header, $body = "")
    {
        if (!$this->smtp_putcmd("HELO", $helo)) {

            return $this->smtp_error("sending HELO command");
        }

        #auth

        if($this->auth){
            if (!$this->smtp_putcmd("AUTH LOGIN", base64_encode($this->user))) {
                return $this->smtp_error("sending HELO command");
            }

            if (!$this->smtp_putcmd("", base64_encode($this->pass))) {
                return $this->smtp_error("sending HELO command");
            }
        }

        #

        if (!$this->smtp_putcmd("MAIL", "FROM:<".$from.">")) {
            return $this->smtp_error("sending MAIL FROM command");
        }

        if (!$this->smtp_putcmd("RCPT", "TO:<".$to.">")) {
            return $this->smtp_error("sending RCPT TO command");
        }

        if (!$this->smtp_putcmd("DATA")) {
            return $this->smtp_error("sending DATA command");
        }


        if (!$this->smtp_message($header, $body)) {


            return $this->smtp_error("sending message");


        }


        if (!$this->smtp_eom()) {


            return $this->smtp_error("sending <CR><LF>.<CR><LF> [EOM]");


        }


        if (!$this->smtp_putcmd("QUIT")) {


            return $this->smtp_error("sending QUIT command");


        }


        return TRUE;


    }


    function smtp_sockopen($address)


    {


        if ($this->relay_host == "") {


            return $this->smtp_sockopen_mx($address);


        } else {


            return $this->smtp_sockopen_relay();


        }


    }


    function smtp_sockopen_relay()


    {


        $this->log_write("Trying to ".$this->relay_host.":".$this->smtp_port."\n");


        $this->sock = @fsockopen($this->relay_host, $this->smtp_port, $errno, $errstr, $this->time_out);


        if (!($this->sock && $this->smtp_ok())) {


            $this->log_write("Error: Cannot connenct to relay host ".$this->relay_host."\n");


            $this->log_write("Error: ".$errstr." (".$errno.")\n");


            return FALSE;


        }


        $this->log_write("Connected to relay host ".$this->relay_host."\n");


        return TRUE;


    }


     


    function smtp_sockopen_mx($address)


    {


        $domain = ereg_replace("^.+@([^@]+)$", "\1", $address);


        if (!@getmxrr($domain, $MXHOSTS)) {


            $this->log_write("Error: Cannot resolve MX \"".$domain."\"\n");


            return FALSE;


        }


        foreach ($MXHOSTS as $host) {


            $this->log_write("Trying to ".$host.":".$this->smtp_port."\n");


            $this->sock = @fsockopen($host, $this->smtp_port, $errno, $errstr, $this->time_out);


            if (!($this->sock && $this->smtp_ok())) {


                $this->log_write("Warning: Cannot connect to mx host ".$host."\n");


                $this->log_write("Error: ".$errstr." (".$errno.")\n");


                continue;


            }


            $this->log_write("Connected to mx host ".$host."\n");


            return TRUE;


        }


        $this->log_write("Error: Cannot connect to any mx hosts (".implode(", ", $MXHOSTS).")\n");


        return FALSE;


    }


     


    function smtp_message($header, $body)


    {


        fputs($this->sock, $header."\r\n".$body);


        $this->smtp_debug("> ".str_replace("\r\n", "\n"."> ", $header."\n> ".$body."\n> "));


     


        return TRUE;


    }


     


    function smtp_eom()


    {


        fputs($this->sock, "\r\n.\r\n");


        $this->smtp_debug(". [EOM]\n");


     


        return $this->smtp_ok();


    }


     


    function smtp_ok()


    {


        $response = str_replace("\r\n", "", fgets($this->sock, 512));


        $this->smtp_debug($response."\n");


     


        if (!ereg("^[23]", $response)) {


            fputs($this->sock, "QUIT\r\n");


            fgets($this->sock, 512);

    
            $this->log_write("Error: Remote host returned \"".$response."\"\n");


            return FALSE;


        }


        return TRUE;


    }


    function smtp_putcmd($cmd, $arg = "")


    {


        if ($arg != "") {


            if($cmd=="") $cmd = $arg;


            else $cmd = $cmd." ".$arg;


        }


        fputs($this->sock, $cmd."\r\n");


        $this->smtp_debug("> ".$cmd."\n");


        return $this->smtp_ok();


    }


    function smtp_error($string)


    {


        $this->log_write("Error: Error occurred while ".$string.".\n");


        return FALSE;


    }


    function log_write($message)


    {


        $this->smtp_debug($message);


        if ($this->log_file == "") {
    

            return TRUE;


        }


        $message = date("M d H:i:s ").get_current_user()."[".getmypid()."]: ".$message;


        if (!@file_exists($this->log_file) !($fp = @fopen($this->log_file, "a"))) {


            $this->smtp_debug("Warning: Cannot open log file \"".$this->log_file."\"\n");


            return FALSE;;


        }


        flock($fp, LOCK_EX);


        fputs($fp, $message);


        fclose($fp);



        return TRUE;


    }



    function strip_comment($address)


    {


        $comment = "\([^()]*\)";


        while (ereg($comment, $address)) {


            $address = ereg_replace($comment, "", $address);


        }



        return $address;


    }



    function get_address($address)


    {


        $address = ereg_replace("([ \t\r\n])+", "", $address);


        $address = ereg_replace("^.*<(.+)>.*$", "\1", $address);


        return $address;


    }


    function smtp_debug($message)


    {


        if ($this->debug) {


        echo $message;


        }


    }


}


?>


//*****************************************************************
// *.php 使用文件，看清楚了，怎么使用在这里
//
//*****************************************************************

<?

require (FILE_DIR."smtp.php");

$smtpserver = "smtp.xxx.com";//SMTP服务器


$smtpserverport =25;//SMTP服务器端口


$smtpusermail = "xxxxx@xxx.com";//SMTP服务器的用户邮箱


$smtpemailto = "aaaaa@xxx.com";//发送给谁


$smtpuser = "xxxxx";//SMTP服务器的用户帐号


$smtppass = "xxxxx";//SMTP服务器的用户密码


$mailsubject = "Test Subject";//邮件主题


$mailbody = "<h1>This is a test mail</h1>";//邮件内容


$mailtype = "HTML";//邮件格式（HTML/TXT）,TXT为文本邮件


$smtp = new smtp($smtpserver,$smtpserverport,true,$smtpuser,$smtppass);//这里面的一个true是表示使用身份验证,否则不使用身份验证.


$smtp->debug = TRUE;//是否显示发送的调试信息


$smtp->sendmail($smtpemailto, $smtpusermail, $mailsubject, $mailbody, $mailtype);


?>