Hmmm... Lets see... You could make a system that used acknowledgements like this:

All ok:
A sends the mail to B, B receives mail, B sends Ack, A receives Ack. A does nothing more. Transaction is successful, both sides know this.

B does not receive:
A sends mail to B, B does not receive, B sends no Ack, A waits for a time out period before resending. After a certain amount of retries, A will know there is an error. Transaction not successful, A most contact B in some other way. B does not know that A has tried to send a mail.

A does not receive:
A sends mail to B, B receives mail, B sends Ack, A does not receive Ack and resends mail, B understands that A did not get Ack and resends Ack, A does not receive Ack and so resends. Transaction was not successful, B know the Acks does not reach A, and so must contact A over an alternate medium, or wait until A contacts him/her.

So, if A does not receive confirmation, A resends a certain number of times, and if that fails turn to an alternate medium or try again at a later time, Unless I missed something, I see no real need for acknowledging Acks... It is sort of like a basic connection oriented protocol, but it will do. How it would tie in with particles and entanglement though, I do not know.

__________________
Game over, you lose, we hope you enjoyed playing the exciting game of Thermodynamics...