php验证邮件地址的有效性

   对于普通的邮件地址，一般都只是做命名合法的有效性，但是对于邮件地址是否存在等无法做有效的验证。通过网上的资料查看以下方式可以进行较完整的验证，但是在测试过程中发现还是不够那么完善，但是此方式是我看到用代码层面去确定的最好方式了：

<?php

 /**
 * Validate Email Addresses Via SMTP
 * This queries the SMTP server to see if the email address isaccepted.
 * @copyright  -Please keep this comment intact
 * @author [e-mail]
 * @contributers [e-mail]
 * @version 0.1a
 */
class SMTP_validateEmail {

      /**
       * PHP Socket resource to remote MTA
       * @var resource $sock
       */
      var $sock;

      /**
       * Current User being validated
       */
      var $user;
      /**
       * Current domain where user is being validated
       */
      var $domain;
      /**
       * List of domains to validate users on
       */
      var $domains;
      /**
       * SMTP Port
       */
      var $port = 25;
      /**
       * Maximum Connection Time to wait for connectionestablishment per MTA
       */
      var $max_conn_time = 30;
      /**
       * Maximum time to read from socket before giving up
       */
      var $max_read_time = 5;

      /**
       * username of sender
       */
      var $from_user = 'user';
      /**
       * Host Name of sender
       */
      var $from_domain = 'localhost';

      /**
       * Nameservers to use when make DNS query for MX entries
       * @var Array $nameservers
       */
      var $nameservers = array(
          '192.168.0.1'
      );

      var $debug = false;

      /**
       * Initializes the Class
       * @return SMTP_validateEmail Instance
       * @param $email Array[optional] List of Emails toValidate
       * @param $sender String[optional] Email of validator
       */
      function SMTP_validateEmail($emails = false, $sender =false)
      {
          if ($emails) {
               $this->setEmails($emails);
          }
          if ($sender) {
               $this->setSenderEmail($sender);
          }
      }

      function _parseEmail($email)
      {
          $parts = explode('@', $email);
          $domain = array_pop($parts);
          $user= implode('@', $parts);
          return array($user, $domain);
      }

      /**
       * Set the Emails to validate
       * @param $emails Array List of Emails
       */
      function setEmails($emails)
      {
          foreach ($emails as $email) {
              list($user, $domain) = $this->_parseEmail($email);
              if (!isset($this->domains[$domain])) {
                    $this->domains[$domain] = array();
              }
              $this->domains[$domain][] = $user;
          }
      }

      /**
       * Set the Email of the sender/validator
       * @param $email String
       */
      function setSenderEmail($email)
      {
          $parts = $this->_parseEmail($email);
          $this->from_user = $parts[0];
          $this->from_domain = $parts[1];
      }

      /**
      * Validate Email Addresses
      * @param String $emails Emails to validate (recipientemails)
      * @param String $sender Sender's Email
      * @return Array Associative List of Emails and theirvalidation results
      */
      function validate($emails = false, $sender = false)
      {

          $results = array();

          if ($emails) {
               $this->setEmails($emails);
          }
          if ($sender) {
               $this->setSenderEmail($sender);
          }

          // query the MTAs on each Domain

          foreach($this->domains as $domain=>$users) {

          $mxs = array();

          // current domain being queried

          $this->domain = $domain;

          // retrieve SMTP Server via MX query on domain

          list($hosts, $mxweights) = $this->queryMX($domain);

          // retrieve MX priorities

          for($n = 0; $n < count($hosts); $n++){
              $mxs[$hosts[$n]] = $mxweights[$n];
          }
          asort($mxs);

          // last fallback is the original domain

          $mxs[$this->domain] = 0;

          $this->debug(print_r($mxs, 1));

          $timeout = $this->max_conn_time;

          // try each host

          while(list($host) = each($mxs)) {
              // connect to SMTP server

              $this->debug("try $host:$this->port\n");
              if ($this->sock = fsockopen($host, $this->port, $errno, $errstr, (float) $timeout)) {
                  stream_set_timeout($this->sock, $this->max_read_time);
                   break;
              }
          }

          //did we get a TCP socket

          if ($this->sock) {
              $reply = fread($this->sock, 2082);
              $this->debug("<<<\n$reply");

              preg_match('/^([0-9]{3}) /ims', $reply,$matches);
              $code = isset($matches[1]) ? $matches[1] : '';

              if($code != '220') {
                  // MTA gave an error...

                  foreach($users as $user) {
                   $results[$user.'@'.$domain] = false;
                   }
                   continue;
              }

              // say helo

              $this->send("HELO ".$this->from_domain);
              // tell of sender

              $this->send("MAIL FROM: <".$this->from_user.'@'.$this->from_domain.">");

              // ask for each recepient on this domain

              foreach($users as $user) {

                   // ask of recepient

                   $reply = $this->send("RCPT TO: <".$user.'@'.$domain.">");

                  // get code and msg from response

                   preg_match('/^([0-9]{3}) /ims', $reply,$matches);
                   $code = isset($matches[1]) ? $matches[1] : '';

                   if ($code == '250') {
                   // you received 250 so the email address was accepted

                        $results[$user.'@'.$domain] =true;
                   }
                   elseif ($code == '451' || $code == '452') {
                        // you received 451 so the email address was greylisted (or some temporary error occured on the MTA) - so assume is ok

                        $results[$user.'@'.$domain] =true;
                   }
                   else {
                        $results[$user.'@'.$domain] =false;
                   }

             }

              // reset before quit

              $this->send("RSET");

              // quit

              $this->send("quit");
              // close socket

              fclose($this->sock);
              }
          }
          return $results;
      }


     function send($msg) {
          fwrite($this->sock, $msg."\r\n");

          $reply = fread($this->sock, 2082);

          $this->debug(">>>\n$msg\n");
          $this->debug("<<<\n$reply");

          return $reply;
     }

      /**
       * Query DNS server for MX entries
       * @return
       */
     function queryMX($domain) {
          $hosts = array();
          $mxweights = array();
          if (function_exists('getmxrr')) {
          getmxrr($domain, $hosts, $mxweights);
     }
     else {
          // windows, we need Net_DNS

          require_once 'Net/DNS.php';

          $resolver = new Net_DNS_Resolver();
          $resolver->debug = $this->debug;
          // nameservers to query

          $resolver->nameservers = $this->nameservers;
          $resp = $resolver->query($domain, 'MX');
              if ($resp) {
                   foreach($resp->answer as $answer) {
                        $hosts[] = $answer->exchange;
                        $mxweights[] = $answer->preference;
                   }
              }

          }
          return array($hosts, $mxweights);
      }

      /**
       * Simple function to replicate PHP 5 behaviour.
       */
     function microtime_float()
     {
       list($usec, $sec) = explode(" ", microtime());
       return ((float)$usec + (float)$sec);
     }

     function debug($str)
     {
          if ($this->debug) {
              echo ''.htmlentities($str).'';
          }
     }
}
?>

//调用例子
<?php

// include SMTP Email Validation Class

require_once('testEmailVaild.php');

// the email to validate

$email = '[e-mail]';
// an optional sender

$sender = '[e-mail]';
// instantiate the class

$SMTP_Validator = new SMTP_validateEmail();
// turn on debugging if you want to view the SMTP transaction

$SMTP_Validator->debug = true;
// do the validation

$results = $SMTP_Validator->validate(array($email),$sender);
// view results

echo $email.' is '.($results[$email] ? 'valid' :'invalid')."\n";

// send email?

if ($results[$email]) {
  //mail($email, 'Confirm Email', 'Please reply to this email to confirm', 'From:'.$sender."\r\n"); // send email

}
else {
  echo 'The email addresses you entered is not valid';
}


?>

以上代码来源于其它地方，由于是上次保持到本地的，已经找不到。若代码所属者看到此代码要求删除可以留言。

    后来在多次的测试中发现，其实sendmail本身对于发送失败的地址会有相关的返回值，此信息可以从$mail->ErrorInfo函数中获取，在failed to load: recipients_字符串后面会有发送失败的地址。我们可以对发送的邮件地址进行多次发送，第一次发送就可以获取失败的地址，然后进行记录并通知，以后的发送读取发送的失败的地址进行过滤。从而可以解决这个问题。相比于上述第一种方法，会多一次发送的时间，但是在准确性方面却有很好的保证。