I have just tried it as that (for the dynamic reply address) and now the form isn't even arriving.
I had already changed the From address to an address from our domain.
Why isn't it sending?
Hope you can help. There seems to be serious problems with Universal E-mail.
EDIT: Just tried it with this:
<?php echo (isset($_POST['Name'])?$_POST['Name']:""); ?> <<?php echo (isset($_POST['Email'])?$_POST['Email']:""); ?>>
...and it also doesn't work. Have exhausted all possibilities here.