Electronic mail (email or email) is a method of exchanging messages (“mail”) between people who use electronic devices. Invented by Ray Tomlinson, email first came into limited use in the 1960s and by the mid-1970s he had taken the form now recognized as email. Email works through computer networks, which today is mainly the Internet. Some previous email systems required the author and the recipient to be online at the same time, as well as instant messaging. The current email systems are based on a storage and forwarding model. Email servers accept, forward, deliver and store messages. It is not required that users or their computers are online simultaneously; they need to connect only briefly, usually to a mail server or a webmail interface, for as long as it is necessary to send or receive messages.
Originally, an ASCII text-only media, Internet email was extended with Multipurpose Internet Mail Extensions (MIME) to transport text in other character sets and multimedia content attachments. International email, with internationalized email addresses using UTF-8, has been standardized, but as of 2017, it has not been widely adopted.
The history of modern Internet e-mail services dates back to ARPANET, with standards for the coding of e-mail messages published since 1973 (RFC 561). An email message sent in the early 1970s looks very similar to a basic email sent today. Email played an important role in the creation of the Internet, and the conversion of ARPANET to the Internet in the early 1980s produced the core of current services.
Computer-based mail and messaging became possible with the advent of timeshare computers in the early 1960s, and informal methods of using shared files to pass messages were soon expanded to the first mail systems. Most mainframe and minicomputer developers developed similar, but generally incompatible, mail applications. Over time, a complex network of gateways and routing systems linked many of them. Many universities in the US UU They were part of ARPANET (created in the late 1960s), whose goal was the portability of software between their systems. That portability helped make the Simple Mail Transfer Protocol (SMTP) increasingly influential.
For a time, in the late 1980s and early 1990s, it seemed likely that a proprietary trading system or X.400 e-mail system, part of the Government’s Open Systems Interconnection Profile (GOSIP), would predominate. ). However, once the final restrictions on transporting commercial traffic over the Internet ended in 1995, a combination of factors converted the current Internet suite of SMTP, POP3, and IMAP email protocols into the rule.
The basic format of Internet email messages is now defined by RFC 5322, with non-ASCII data encoding and media content attachments defined in RFC 2045 to RFC 2049, collectively referred to as Multipurpose Internet Mail Extensions or MIME. RFC 5322 replaced the previous RFC 2822 in 2008 and, in turn, RFC 2822 in 2001 replaced RFC 822, which had been the standard for Internet email for almost 20 years. Published in 1982, RFC 822 was based on the previous RFC 733 for ARPANET.
Internet email messages consist of two main sections, the message header and the body of the message, collectively known as content. The header is structured in fields such as From, To, CC, Subject, Date and other information about the email. In the process of transporting e-mail messages between systems, SMTP communicates delivery parameters and information through the header fields of the message. The body contains the message, as unstructured text, which sometimes contains a signature block at the end. The header is separated from the body by a blank line.