php有一个mail()函数，可以用来发邮件，但是在系统里面需要进行详细的配置。如果在windows系统里面还有安装sendmail软件。而且一个服务器上只能统一使用相同是smtp来发送邮件。无法满足更复杂的需求。

网上有一个smtp发邮件的组件，叫jmail，在asp和asp.net里面非常流行这个组件。在php中，也可以使用com对象来调用jmail的功能。不过jmail是一个dll组件，貌似只能在windows里面使用。我们写php的系统，肯定希望在windows或linux上尽可能都能兼容，所以，这个也放弃了。

最后，范围就很小了。只能自己来实现一个smtp发邮件的功能。正好在网上找到一个email.class.php的类。它貌似最早由一个外国人写的，可以完全模拟smtp发邮件。调用时，传递smtp服务器地址、端口、用户名、密码、发件人、收件人、主题、内容、邮件类型等，非常方便。同一个服务器不同的应用，可以同一个应用的不同模块，都可以自由的调用。

源码如下：

<?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;

}
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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;

}

}

}

?>