on the tilattu_ok.php page, you have the universal email behavior set to trigger on the checkout button being pressed.
The checkout page will not trigger this because the checkout form action is to post to itself:
<form action="" method="post" >
it then redirects to the tilattu_ok.php, change the forms action to post to the tilattu_ok.php page instead:
<form action="tilattu_ok.php" method="post" >