elimde bir script var mail yollamak için fakat text yolluyor.Giden texti html destekli yapmamız mümkünmü?

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=windows-1254" />
<title>Megaturks Toplu Mail 2.0</title>
<style type="text/css">
<!--
.Yazi {
	font-family: "Palatino Linotype", "Book Antiqua", Palatino, serif;
	font-size: 24px;
	font-weight: bold;
	color: #FFF;
	text-align: center;
}
.table {
	background-color:#0FF;
	margin:auto;
	border:3px solid #FFF;
}
.body{
	background-color:#CCC;
}
.anatut{
	margin-top:60px;
}
.icyazi {
	font-family: "Palatino Linotype", "Book Antiqua", Palatino, serif;
	font-size: 14px;
	color: #00F;
	text-align: center;
	padding: 5px;
	font-weight: bolder;
}
.durum{
	background-color:#00F;
	font:"Palatino Linotype", "Book Antiqua", Palatino, serif;
	color:#FFF;
	font-size: 14px;
	text-align:center;
	padding:2px;
	width:200px;
	margin:auto;
	border:1px solid #FFF;
}
.submit {
	font-family: "Palatino Linotype", "Book Antiqua", Palatino, serif;
	color: #00F;
	background-color: #FFF;
	width:150px;
	text-align:center;
	font-weight:bold;
}
.input {
	background-color: #FFF;
	width: 250px;
}
-->
</style>
</head>
<script type="text/javascript">
function durumdegis(simdi,toplam){
  document.getElementById("durum").innerHTML="Durum ("+simdi+"/"+toplam+")";
}
</script>
<body class="body">
<div class="anatut">
<table width="600" border="0" cellpadding="0" cellspacing="0" class="table">
  <tr>
    <td colspan="3" class="Yazi"><p>Megaturks Toplu Mail 2.0</p>
 </td>
  </tr>
  <tr>
 <td colspan="3">
<div class="durum" id="durum"></div>
   </td>
  </tr>
  <tr>
    <td width="124" class="icyazi">Gonderen</td>
    <td width="3">:</td>
    <td width="467">
	<form method="post" action="">
      <label>
        <input name="gonderen" type="text" class="input" id="gonderen" />
      </label>
</td>
  </tr>
  <tr>
    <td class="icyazi">Baslık</td>
    <td>:</td>
    <td>
      <label>
        <input name="baslik" type="text" class="input" id="baslik" />
      </label>
</td>
  </tr>
  <tr>
    <td class="icyazi">Mesaj</td>
    <td>:</td>
    <td>
      <label>
        <textarea name="mesaj" id="mesaj" cols="50" rows="10"></textarea>
      </label>
</td>
  </tr>
  <tr>
    <td class="icyazi">Mail Listesi</td>
    <td>:</td>
    <td>
      <label>
        <input name="maillist" type="text" class="input" id="maillist" />
      </label>
</td>
  </tr>
  <tr>
      <p>
	 <td colspan="3">
        <label>
    <center><input type="submit" name="gonder" class="submit" value="Baslat" /></center>
          </label>
        </p>
      <p>&nbsp;</p>
      </form></td>
  </tr>
</table>
</div>
</body>
</html>
<?php
//Kodlayan : KıLıCaRsLaN
//Tesekkur : RMx - h4ckinger - kerem125
ob_start();
ini_set('max_execution_time',0);
error_reporting (0);
		if (isset ($_POST ["gonder"]))
{
$alici		=$_POST ["maillist"];
$aclist=file_get_contents ($alici);
$sonalici=trim ($aclist);
$sonalici=explode("\n",$sonalici);
$toplam=count($sonalici);
$i=1;
		Foreach ($sonalici as $teslim)
{	
$mesaj		=$_POST ["mesaj"];
$mesaj		=str_replace("\n","<br>",$mesaj);
$gonderen	=$_POST ["gonderen"];
$baslik		=$_POST ["baslik"];
//baslıklar
$ustkisim  = 'MIME-Version: 1.0' . "\n";
$ustkisim .= 'Content-type: text/html; charset=iso-1254' . "\n";
$ustkisim .= "To: ".$teslim." " . "\n"; 
$ustkisim .= "From: ".$gonderen." " . "\n";
$ustkisim .= 'Reply-To: help@microsoft.com' . "\n";
$ustkisim .= 'X-Mailer: PHP/5\n';
		mail($teslim, $baslik, $mesaj, $ustkisim);
		if (($teslim=="") || ($mesaj=="") || ($baslik=="") || ($gonderen==""))
		{
		
		echo '<script>alert("Niye bos yer bırakıyosun hepsini doldur")</script>';
		die();
		}
		if(!$teslim)
		{
		$sonuc="basarisiz.doc";
		touch ($sonuc);
		$dosya= fopen($sonuc,"a") or die ("<b>Dosyaya Yazılamıyor</b>");
		fwrite($dosya,$bak."\n");
		}
			echo '<script language="javascript" type="text/javascript">durumdegis("'.$i.'","'.$toplam.'");</script>';
			ob_flush();
			flush();
			
		$i++;
}
}
?>