Same sort of switch case logic. in the WA_Universal_Email/WAUE_contact_1.php file, change:
$MailSubject = "".($WAGLOBAL_Contact_Email_Subject) ."";
to:
$MailSubject = "Default Subject";
if(isset($_POST['sendTo']) && $_POST['sendTo'] != "") {
switch($_POST['sendTo']) {
case "sales@domain.com":
$MailSubject = "Sales Subject";
break;
case "service@domain.com":
$MailSubject = "Service Subject";
break;
case "support@domain.com":
$MailSubject = "Support Subject";
break;
}
}