Risks to user

The pathway of e-mail. Terminology used in this image is explained in the electronic mail article.
Because e-mail connects through many routers and mail servers on its way to the recipient, it is inherently vulnerable to both physical and virtual eavesdropping. Current industry standards do not place emphasis on security; information is transferred in plain text, and mail servers regularly conduct unprotected backups of e-mail that passes through. In effect, every e-mail leaves a digital papertrail in its wake that can be easily inspected months or years later.
The e-mail can be read by any cracker who gains access to an inadequately protected router. Some security professionals argue that e-mail traffic is protected from such "casual" attack by security through obscurity - arguing that the vast numbers of e-mails make it difficult for an individual cracker to find, much less to exploit, any particular e-mail. Others argue that with the increasing power of personal computers and the increasing sophistication and availability of data-mining software, such protections are at best temporary.
Intelligence agencies, using intelligent software, can screen the contents of e-mail with relative ease. Although these methods have been decried by civil rights activists as an invasion of privacy, agencies such as the U.S. Federal Bureau of Investigation conduct screening operations regularly.
ISPs and mail service providers may also compromise e-mail privacy because of commercial pressure. Many online e-mail providers, such as Yahoo! Mail or Google's Gmail, display context-sensitive advertisements depending on what the user is reading. While the system is automated and typically protected from outside intrusion, industry leaders have expressed concern over such data mining.
The receivers of e-mail can compromise e-mail privacy by indiscrimate forwarding of e-mail. This can reveal contact information (like e-mail addresses, full names, and phone numbers), internal use only information (like building locations, corporate structure, and extension numbers), and confidential information (trade secrets and planning).
In the United States and some other countries lacking secrecy of correspondence laws, e-mail exchanges sent over company computers are considered company property and are thus accessible by management. Employees in such jurisdictions are often explicitly advised that they may have no expectation of a right to privacy for messages sent or received over company equipment. This can become a privacy issue if employee and management expectations are mismatched.

Remedies

To provide a reasonable level of privacy, all routers in the e-mail pathway, and all connections between them, must be secured. This is done through data encryption, which translates the e-mail's contents into incomprehensible text that, if designed correctly, can be decrypted only by the recipient. An industry-wide push toward regular encryption of e-mail correspondence is slow in the making. However, there are certain standards that are already in place which some services have begun to employ.There are two basic techniques for providing such secure connections. The first involves encrypting the message directly using a secure encryption standard such as OpenPGP (Public key infrastructure) or S/MIME. These encryption methods are often a user-level responsibility, even though Enterprise versions of OpenPGP exist. The usage of OpenPGP requires the exchange of encryption keys. Even if the encrypted emails are intercepted and accessed, its contents are meaningless without the encryption key.This method is also sometimes tied with authentication. Authentication just means that each user must prove who they are by using either a password, biometric (such as a fingerprint), or other standard authentication means.The second approach is to send an open message to the recipient which contains no sensitive content but which announces a message waiting for the recipient on the sender's secure mail facility. The recipient then follows a link to the sender's secure website where the recipient must log in with a username and password before being allowed to view the message.At the ISP level, a further level of protection can be implemented by encrypting the communication between servers themselves, usually employing an encryption standard called Transport Layer Security (TLS). It is coupled with Simple Authentication and Security Layer (SASL), which confirms the target router's identity. This ensures that unintended servers don't end up with a copy of the e-mail, which happens frequently in the course of normal correspondence.Although many ISPs have implemented secure sending methods, users have been slow to adopt the habit, citing the esoteric nature of the encryption process. Without user participation, e-mail is only protected intermittently from intrusion.