Valid email address correctly (PHP)

Nowadays, valid the format of the email is not enough, so, we need to valid it with making a testing connection to the email server and ask the email server that the user provided if the email account exisit! Here is a PHP function that can do this for you:

<?php

/* Return value: (true|false)
   true if valid, false if invalid */

function valid_email($email)
{
    global $HTTP_HOST;

    if (!eregi("^[_a-z0-9-]+(.[_a-z0-9-]+)*@[a-z0-9-]+(.[a-z0-9-]+)*(.[a-z]{2,3})$", $email)) {       
        return false;
    }

    list($username,$domain) = split("@",$email);

    if (checkdnsrr($Domain,"MX")) {
        getmxrr ($Domain, $mxhost);
        $host = $mxhost[0];
    }
    else {
        $host = $domain;         
    }

    $connect = fsockopen($host,25};
    if ($connect) {
        if (ereg("^220", $returns=fgets($connect,1024))) {
            fputs($connect,'HELO ' . $HTTP_HOST . "\r\n");
            $returns = fgets ($connect,1024);
            fputs($connect,'MAIL FROM: <' . $email . ">\r\n");
            $test1 = fgets($connect,1024);
            fputs ($connect,'RCPT TO: <' . $email . ">\r\n");
            $test2 = fgets($connect,1024);
            fputs ($connect,"QUIT\r\n");
            fclose($connect);
            if ((!ereg("^250",$test1)) or (!ereg("^250",$test2))) {
                return false;
            }
        }
    }
    else {
        return false;
    }
    return true;
}

?>