Do you know if unauthorised parties have ever accessed messages or transactions that you have sent over the Internet?
Does only the intended recipient have the ability to read your message?
Digital certificates provide the mechanism to protect information. Messages can be encrypted to minimise the risk that they can be read in transit, or by anyone, other than the intended recipient. This provides the digital equivalent of a registered letter sent through the post.
Public key infrastructure (PKI) can be used to increase the privacy of messages.