ส่ง email ไม่ได้ครับ

contact.html
<form action="sendemail.php" method="post" name="frmMain">
				<table>
					<tr>
						<td><label for="name"><strong>ชื่อ - สกุล:<strong></label></td>
						<td><input name="txtname" type="name" id="name" maxlength="30" /> </td>
						<td><label class="email" for="email">อีเมล์:</label></td> 
						<td><input name="txtemail" type="text" id="email" maxlength="30" /></td>
					</tr>
                    <tr>
						<td><label for="addr"><strong>ที่อยู่:<strong></label></td>
					  <td><input name="txtaddr" type="text" id="addr" maxlength="30" /> </td>
						<td align="right"><label class="tel" for="tel"><strong>โทรศัพท์:</strong></label></td> 
					  <td><input name="txttel" type="text" id="tel" maxlength="30" /></td>
					</tr>
					<tr>
						<td><label for="subject"><strong>หัวข้อ:</strong></label></td>
						<td><input name="txtsubject" type="text" id="subject" maxlength="30" /></td>
					</tr>
					<tr>
						<td class="message" valign="top"><label for="message"><strong>ข้อความ:</strong></label></td>
						<td colspan="3"><textarea name="txtmessage" id="message" cols="30" rows="10"></textarea></td>
					</tr>
					<tr>
						<td></td>
						<td colspan="1">&nbsp;</td>
                        <td></td>
                        <td><input name="submit" type="submit" id="send" /></td>
					</tr>
				</table>
			</form>

<?
	$strTo = "armiiz1991@gmail.com";
	$strName = $_POST["txtname"];
	$strEmail = $_POST["txtemail"];
	$strAddr = $_POST["txtaddr"];
	$strTel = $_POST["txttel"];
	$strSubject = $_POST["txtsubject"];
	$strHeader = "Content-type: text/html; charset=windows-874
"; // or UTF-8 //
	$strHeader .= "".$_POST["txtname"]."<".$_POST["txtemail"].">
Reply-To: ".$_POST["txtemail"].$_POST["txtaddr"].$_POST["txttel"].$_POST["txtsubject"]."";
	$strMessage = nl2br($_POST["txtmessage"]);
	$flgSend = @mail($strTo,$strName,$strEmail,$strAddr,$strSubject,$strMessage,$strHeader);  // @ = No Show Error //
	if($flgSend)
	{
		echo "<script language="javascript"> alert('Email Sending');</script>";
		echo "<script language="javascript">window.location = 'contact.html'</script>";
	}
	else
	{
		echo "<script language="javascript"> alert('Email Can Not Sending');</script>";
		echo "<script language="javascript">window.location = 'contact.html'</script>";
	}
?>