The thing I've always worried about is that to my knowledge there's no ACK for outbound mail. The potential impact of one email I send not being received is ab

The thing I've always worried about is that to my knowledge there's no ACK for outbound mail. The potential impact of one email I send not being received is absolutely enormous to the extent that certain mails I'd pay a decent amount of money to ensure delivery, probably more than an actual postage stamp.