Post some snippit of how you retrieve it. What you could do is something like:
<?php
$username = md5($_POST['user']);
$password = md5($_POST['pass']);
$other = $_POST['otherjunk'];
mail($someone, $someone, $subject, $username.$password.$other);
?>
If I get you, you just want the username and password encoded.
If you want everything encoded, why email it to yourself?
~Brett