More email is lost than I thought. The loss rate is at least 0.7%, or 7 messages in 1,000 . If you send ten messages a day, this means 25 will go astray in a year.
For comparison, airlines operate with 3 to 10 lost baggage reports per 1,000 passengers on major airlines .
As for the old-fashioned way of doing it: the British Royal Mail has admitted that more than 14 million letters and parcels were lost, stolen, damaged or tampered in 2005, out of 22 billion items handled. That’s 0.06% -- ten times better than email!
 Research cited in Sharad Agarwal, Venkata N. Padmanabhan and Dilip A. Joseph, SureMail: Notification Overlay for Email Reliability: “Afergan and
 CNNMoney.com, Grumbling grows among airline passengers, 17 Feb 2006 citing US DoT statistics. The loss rate in terms of bags checked will be different, but hard to know how: increasing numbers of people don't check luggage, reducing baggage/passengers; but those who do check luggage usually check multiple pieces.
 BBC News, Royal Mail fined for missing post, 10 Feb 2006