php mail konusunda yardım

<?
include_once("conn.php");

if (isset($_POST[s1]))
{
	$Username = strip_tags($_POST[username]);

	if(empty($Username))
	{
		$error = "Enter your username!";
	}
	else
	{
		$q1 = "select * from counter_members where username = '$Username' ";
		$r1 = mysql_query($q1) or die(mysql_error());

		if(mysql_num_rows($r1) == '1')
		{
			if($a1 = mysql_fetch_array($r1))
			{
				//send an email
				$to = $a1[EmailAddress];
				$subject = "Your password at $_SERVER[HTTP_HOST]";
				$message = "Hello $a1[Names],\nhere is your login information for $_SERVER[HTTP_HOST]\n\nUsername: $a1[username]\nPassword: $a1[password]\n\nTo login, follow this link:\nhttp://$_SERVER[HTTP_HOST]/login.php\n\nThank you for your registration!";

				$headers = "MIME-Version: 1.0\n"; 
				$headers .= "Content-type: text/plain; charset=iso-8859-1\n";
				$headers .= "Content-Transfer-Encoding: 8bit\n"; 
				$headers .= "From: $_SERVER[HTTP_HOST] <$aset[ContactEmail]>\n"; 
				$headers .= "X-Priority: 1\n"; 
				$headers .= "X-MSMail-Priority: High\n"; 
				$headers .= "X-Mailer: PHP/" . phpversion()."\n"; 

				mail($to, $subject, $message, $headers);		

				header("location:forgot_ok.php?to=$to");
				exit();
			}
		}
		else
		{
			$error = "Invalid Username!";
		}

	}
}

include_once("includes.php");
include_once("template/header.php");
include_once("template/forgot_template.php");
include_once("template/footer.php");
?>

  <?php

$to = "gondermek-istediginiz-adres@alan-adi.com";
$subject = "Test";
$message = "Test..\nwww.isimtescil.net";

$headers = "From: size-ait-adres@alan-adiniz.com\r\n";
$headers .= "Reply-To: size-ait-adres@alan-adiniz.com\r\n";
$headers .= "Return-Path: size-ait-adres@alan-adiniz.com\r\n";

if ( mail($to,$subject,$message,$headers) ) {
   echo "Email gönderildi..";
   } else {
   echo "Email gönderilemedi!!!";
   }
?>