How to let Sender know Recipient isn't receiving message?

PHP
7

Like this?

//....

$_SESSION[‘update_token’] = ‘’;
$show_form = 0;
}

} else {

//User is Not Accepting emails.

echo "This person is not receiving emails.";

// START SHOW MESSAGE COMPOSE FORM
// Get to_id

$show_form	= 1;
//....