Merhaba.
Cevabınız için teşekkür ederim. Örnek kodlar yardımı ile herhalde girişi sağladım fakat bomboş bir ekran görünüyor. Kullandığım kodlar aşağıdadır. Ben nerede eksik yapıyorum? Teşekkürler.

<?
error_reporting(0);  
function get_headers_from_curl_response($headerContent)
{

    $headers = array();

    // Split the string on every "double" new line.
    $arrRequests = explode("\r\n\r\n", $headerContent);

    // Loop of response headers. The "count() -1" is to 
    //avoid an empty row for the extra line break before the body of the response.
    for ($index = 0; $index < count($arrRequests) -1; $index++) {

        foreach (explode("\r\n", $arrRequests[$index]) as $i => $line)
        {
            if ($i === 0)
                $headers[$index]['http_code'] = $line;
            else
            {
                list ($key, $value) = explode(': ', $line);
                $headers[$index][$key] = $value;
            }
        }
    }

    return $headers;
}
function regexExtract($text, $regex, $regs, $nthValue)
{
    if (preg_match($regex, $text, $regs)) {
        $result = $regs[$nthValue];
    }
    else {
         $result = "";
    }
return $result;
}
$regexViewstate = '/__VIEWSTATE\" value=\"(.*)\"/i';
$regexEventVal  = '/__EVENTVALIDATION\" value=\"(.*)\"/i';

$ch = curl_init("http://mail.burulas.com.tr/Mondo/lang/sys/Login.aspx");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_HEADER, 1);
curl_setopt($ch, CURLOPT_COOKIEJAR, 'cookies.txt');

$response = curl_exec($ch);
curl_close($ch);

$viewstate = regexExtract($response,$regexViewstate,$regs,1);
$eventval = regexExtract($response, $regexEventVal,$regs,1);

$params = array(
    '__EVENTTARGET' => '',
    '__EVENTARGUMENT' => '',
    '__VIEWSTATE' => $viewstate,
    '__EVENTVALIDATION' => $eventval, 
    'txtUsername' => 'login',
    'txtPassword' => 'pass',
    'dlLanguages' => 'tr',
    'ddlSkins' => 'Mondo',
	'loginParam' => 'SubmitLogin',
);

$ch2 = curl_init("http://mail.burulas.com.tr/Mondo/lang/sys/Login.aspx");
curl_setopt($ch2, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch2, CURLOPT_HEADER, 1);
curl_setopt ($ch2, CURLOPT_POST, true);
curl_setopt($ch2, CURLOPT_SSL_VERIFYPEER, FALSE);
curl_setopt($ch2, CURLOPT_POSTFIELDS, http_build_query($params));
curl_setopt ($ch2, CURLOPT_COOKIE,'cookies.txt');
curl_setopt($ch2,CURLOPT_COOKIEJAR,'cookies2.txt');

$response2 = curl_exec($ch2);
curl_close($ch2);

foreach(get_headers_from_curl_response($response2) as $value)
{
    foreach($value as $key => $value2)
    {
        echo $key . ": " .$value2 . "<br />";
    }
}
preg_match_all('@<span id="lUsage">(.*?)</span>@si',$response2,$veri_derece1);

echo $veri_derece1[0][0];

?>

İstediğim lUsage kısmını ekrana yansıtmak hepsi o.

Ekranın bana çıkardığı yazı da aşağıdadır.

http_code: HTTP/1.1 100 Continue
http_code: HTTP/1.1 302 Found
Cache-Control: private
Content-Length: 153
Content-Type: text/html; charset=utf-8
Location: /Mondo/lang/sys/default.aspx
Server: Microsoft-IIS/7.5
X-AspNet-Version: 2.0.50727
Set-Cookie: NSC_DMVTUFS13_XFCNBJM=ffffffff5d41a04b45525d5f4f58455e445a4a423660;expires=Mon, 23-Mar-2015 16:19:20 GMT;path=/;httponly
X-Powered-By: ASP.NET
Date: Mon, 23 Mar 2015 15:49:58 GMT

Ekranın çıktısı da bu. Teşekkürler.