ส่ง email error ครับ แก้ยังไงดี ผมลองดูตามที่ ทางเว็บสอนแล้วทำไม่ได้อ่ะครับ

<meta charset="UTF-8" />
<?php require_once('../../Connections/con_shop.php'); ?>
<?php @session_start(); ?>
<!------------------------------------------------------------------------------------------------------------------------------->
<?php
//--------------------------------------------------------------------------------------------------------------------------------
$wu_shopname = $_POST['txt_wu_shopname'];
$wu_name = $_POST['txt_wu_name'];
$wu_username = $_POST['txt_wu_username'];
$wu_password = md5($_POST['txt_wu_password']);
$wu_email = $_POST['txt_wu_email'];
$wu_phone = $_POST['txt_wu_phone'];
$wu_address = $_POST['txt_wu_address'];
//--------------------------------------------------------------------------------------------------------------------------------
		$sql = "
		INSERT INTO web_user
		(wu_shopname, wu_name, wu_username, wu_password, wu_email, wu_phone, wu_address, wu_active, wu_detail)
		VALUES
		('$wu_shopname', '$wu_name', '$wu_username', '$wu_password', '$wu_email', '$wu_phone', '$wu_address', 'no', '')
		";

	$result = mysql_db_query($database_shop, $sql) or die("Error in query : $sql" .mysql_error());
//--------------------------------------------------------------------------------------------------------------------------------
			$Uid = mysql_insert_id();
		echo "Register Completed!<br>Please check your email to activate account";		

		$strTo = $_POST['txt_wu_email'];
		$strSubject = "Activate Member Account";
		$strHeader = "Content-type: text/html; charset=UTF-8"; // or UTF-8 //
		$strHeader .= "From: shopmanagement <[email protected]>";
		$strMessage = "";
		$strMessage .= "Welcome : ".$_POST["txt_wu_name"]."<br>";
		$strMessage .= "=================================<br>";
		$strMessage .= "Activate account click here.<br>";
		$strMessage .= "../../activate.php?sid=".session_id()."&uid=".$Uid."<br>";
		$strMessage .= "=================================<br>";
		$strMessage .= "ThaiCreate.Com<br>";

		$flgSend = mail($strTo,$strSubject,$strMessage,$strHeader); 
		
		if($flgSend)
	{
		echo "Email Sending.";
	}
	else
	{
		echo "Email Can Not Send.";
	}

		mysql_close();
?>

<?php
$to      = '[email protected]';
$subject = 'the subject';
$message = 'hello';
$headers = 'From: [email protected]' . "\r\n" .
    'Reply-To: [email protected]' . "\r\n" .
    'X-Mailer: PHP/' . phpversion();

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