for that you will need to create a switch case statement to select which email address to use in universal Email. The example code below is based on the select list being named "select"
<?php
switch($_POST["select"]) {
case 1:
$email = "sales@email.com";
break;
case 2:
$email = "support@email.com";
break;
case 3:
$email = "marketing@email.com";
break;
default:
$email = "sales@email.com";
break;
}
?>
then modify the universal Email code to use the $email variable:
$RecipientEmail = "".($email) ."";include("WA_Universal_Email/WAUE_contact_1.php");