The trick is to recycle the birds! Just pay an extra few coppers for a return receipt. Then have the recipient reject the receipt. The bird will return without confirmation of delivery. Then you can dispute the transaction and request a new message to be sent, for free, since the first one was obviously not delivered.
And if the bird does happen to have the return receipt, well, pidgeon tastes great. Then you can claim no receipt and request another message.
Or something diabolical like that
