[Guvante]

Physical mail is much simpler than electronic mail. Telegrams are more akin to email that an actual piece of mail.

How do I guarantee I don't look at it when I literally have to look at it to provide the service?

There are services which avoid this by using thinner servers, but they are in the minority.

[nhaehnle]

True. Though the comparison I would make is with postcards, and there is still an expectation of privacy there. If somebody in the postal service were found to be reading postcards on purpose, there would be consequences. Intent matters.