<form action="check.php" method="post">
<table border="0" cellpadding="2" cellspacing="0" width="160">
<tbody>
<tr>
<td><label for="user_login">Email : </label></td>
<td> <input id="user" name="user" class="textbox" value="" tabindex="10" type="text"></td>
</tr>
<tr> 
<tr>
<td align="right" valign="top" colspan="2">
<input name="submit" id="submit" value="ok" class="giris" tabindex="100" type="submit"></td>
 </tr>
</tbody></table>
</form>

<?
if(!$user){
header("Location: index.php");
}
else {
$headers = "From: xxx@xxx.com";
$subject = "konu";
$body = "mesaj";
mail($user, $subject, $body, $headers);
header("Location: index.php");
}
?>