E-mail privacy

The protection of electronic mail from unauthorized access and inspection is known as electronic privacy. In countries with a constitutional guarantee of the secrecy of correspondence, e-mail is equated with letters and thus legally protected from all forms of eavesdropping.
In the United States, privacy of correspondence is derived from the Fourth Amendment to the United States Constitution and thus restricted by the requirement for a "reasonable expectation of privacy".
In France, an important precedent was set in 2000 when a criminal court found three senior academics at the École Supérieure de Physique et de Chimie Industrielles de la Ville de Paris (ESPCI), guilty of espionage on the email of a doctoral researcher. The ruling, which was confirmed by the Criminal Court of Appeals of Paris in 2001, effectively made unauthorised eavesdropping on email a crime equivalent to unauthorised tapping of phone lines and steaming open letters.

Need

The Internet is an expansive network of computers, much of which is unprotected against malicious attacks. From the time it is composed to the time it is read, e-mail travels along this unprotected Internet, perpetually exposed to electronic dangers.
Many users believe that e-mail privacy is inherent and guaranteed, psychologically equating it with postal mail. While e-mail is indeed conventionally secured by a password system, the one layer of protection is not secure, and generally insufficient to guarantee appreciable security.
Businesses are increasingly relying on electronic mail to correspond with clients and colleagues. As more sensitive information is transferred online, the need for e-mail privacy becomes more pressing.