Email encryption

Email encryption is encryption of email messages to protect the content from being read by entities other than the intended recipients. Email encryption may also include authentication. Email is prone to the disclosure of information. Most emails are encrypted during transmission, but they are stored in clear text, making them readable by third parties such as email providers. By default, popular email services such as Gmail and Outlook do not enable end-to-end encryption. By means of some available tools, persons other than the designated recipients can read the email contents. Email encryption can rely on public-key cryptography, in which users can each publish a public key that others can use to encrypt messages to them, while keeping secret a private key they can use to decrypt such messages or to digitally encrypt and sign messages they send. With the original design of email protocol, the communication between email servers was in plain text, which posed a huge security risk. Over the years, various mechanisms have been proposed to encrypt the communication between email servers. Encryption may occur at the transport level (aka "hop by hop") or end-to-end. Transport layer encryption is often easier to set up and use; end-to-end encryption provides stronger defenses, but can be more difficult to set up and use. One of the most commonly used email encryption extensions is STARTTLS. It is a TLS (SSL) layer over the plaintext communication, allowing email servers to upgrade their plaintext communication to encrypted communication. Assuming that the email servers on both the sender and the recipient side support encrypted communication, an eavesdropper snooping on the communication between the mail servers cannot use a sniffer to see the email contents. Similar STARTTLS extensions exist for the communication between an email client and the email server (see IMAP4 and POP3, as stated by RFC 2595). STARTTLS may be used regardless of whether the email's contents are encrypted using another protocol.