<?php
   if ($senden) {
      $sender = "your name";
      $sendermail = "info@bla.net";
      $betreff = "bla bla bla testmail";
      $text = "Testmail from bitbin.it";

      $header = "From: \"".$sender."\" <".$sendermail.">\n";
      mail($empfaenger, $betreff, $text, $header);
      echo "Mail send!<BR><BR>";
   }
   else {
?>

<form action="<?php $PHP_SELF; ?>"method="post">
your mail adress:<BR>
<input type="Text" name="empfaenger" size="30">
<input type="Submit" name="senden" value="Senden">
</form>

<?
   }   
?>