Email (also written e-mail) is a system for sending and receiving messages electronically over a computer network. It was one of the first technologies developed for the Internet.
With email, you can compose messages and address them to any person in the world who also uses email, regardless of the brand or type of email technology the recipient uses. You can also receive messages from any other email user. The messages transmitted and received via the email system are also called emails. A user name displayed with a domain name is called an email address or email account.
To send or receive email you need an Internet connection and email software, also known as an email client. Because it’s so convenient and easy to use, email has rapidly become part of everyday life. This widespread use also makes it a primary target for attackers.
The email system was designed originally to transmit text only. Currently, an email message can contain other files, known as attachments, in addition to the message, such as documents, graphics, music and video. To display an email message in a specific layout, font or color or with images, a user can format it in hypertext markup language (HTML), which is a type of code commonly used to create web pages.
The first step in order to have access to the email system is to have an email account. In many cases, employers offer email accounts to their employees. Internet search engine companies such as Hotmail, Yahoo!, Google and many others offer free webmail email service. With webmail, you visit a Web site to read, send and receive your email using nothing more than web browser software. The webmail email system works even when you are not connected to the site, so that you still receive messages if you are not logged in. With an email system, you establish a username and a password for authentication.
An email message has the following fields:
- To: The address or addresses to which the message is to be sent.
- Cc (courtesy/carbon copy): Email addresses of additional recipients, who may have an indirect interest or need for the information in the email message. Note that the recipients in the To and Cc fields will be able to see each other's addresses in the email message.
- Bcc (blind courtesy/carbon copy): Email addresses of additional recipients whose email addresses will not be visible to the recipients in the To or Cc field.
- Subject: The topic of the message.
- Body (a box below the above): The message to be sent.
Given its ubiquity, email is one of the most vulnerable technologies. Among the most common security and privacy issues for email are spam, phishing and attachments. (Please check “Protective Measures” under the encyclopedia entry for malware.)
Email presents many privacy-related vulnerabilities. By default, the contents of an email message are not encrypted. This means that anybody sniffing on the network could have access to them. Additionally, the messages pass through several computers along the way to the destination. To secure emails, a client can use Pretty Good Privacy (PGP) to encrypt and secure the messages. Another alternative used by companies is to use a Virtual Private Network (VPN).