用curl无法模拟登录139邮箱

$ch = curl_init( );
		$headers_login = array(
	                     'Host'  => 'mail.10086.cn',
	                     'User-Agent'      => 'Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; .NET CLR 2.0.50727; MS-RTC LM 8; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729; CIBA)',
	                     'Accept'          => 'image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, application/x-shockwave-flash, application/msword, application/vnd.ms-excel, application/vnd.ms-powerpoint, application/x-ms-application, application/x-ms-xbap, application/vnd.ms-xpsdocument, application/xaml+xml, */*',
	                     'Accept_Language' => 'zh-cn',
	                     'Accept_Encoding' => 'gzip,deflate',
//	                     'Accept_Charset'  => 'GB2312,utf-8;q=0.7,*;q=0.7\r\n',
//	                     'Keep-Alive'      => '115',
	                     'Connection'      => 'keep-alive',
	                     'Content-Length'      => '50',
	                     'Content-Type'      => 'application/x-www-form-urlencoded',
//	                     'X-Requested-With'=> 'XMLHttpRequest',
	                     'Content_Type'    => 'application/x-www-form-urlencoded',
	                     'Cache-Control'    => 'no-cache',
	                     'Referer'         => 'http://mail.10086.cn/'
	                 );
		curl_setopt($ch, CURLOPT_HTTPHEADER, $headers_login);  
		curl_setopt($ch,CURLOPT_HEADER,1);
		curl_setopt( $ch, CURLOPT_URL, "https://mail.10086.cn/Login/Login.ashx" );
//		curl_setopt( $ch, CURLOPT_USERAGENT, USERAGENT );
		curl_setopt( $ch, CURLOPT_POST, 1 );
		curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
		curl_setopt( $ch, CURLOPT_COOKIEJAR, COOKIEJAR );
		curl_setopt( $ch, CURLOPT_TIMEOUT, TIMEOUT );
		$fileds = "UserName=null&Password=null";
		$fileds .= "&VerifyCode";
		curl_setopt( $ch, CURLOPT_POSTFIELDS, $fileds );
		ob_start( );
		curl_exec( $ch );
		$str = curl_exec($ch);
		echo $str;exit;
		$result = ob_get_contents( );
		ob_end_clean( );
		curl_close( $ch );