Electronic mail (E-mail)

Electronic mail (E-mail), most commonly referred to as email or e-mail since approximately 1993, is a method of exchanging digital messages from an author to one or more recipients. Modern email operates across the Internet or other computer networks. Some early email systems required that the author and the recipient both be online at the same time, in common with instant messaging. Today's email systems are based on a store-and-forward model. Email servers accept, forward, deliver, and store messages. Neither the users nor their computers are required to be online simultaneously; they need connect only briefly, typically to an email server, for as long as it takes to send or receive messages.

Historically, the term electronic mail was used generically for any electronic document transmission. For example, several writers in the early 1970s used the term to describe fax document transmission. As a result, it is difficult to find the first citation for the use of the term with the more specific meaning it has today.

An Internet email message consists of three components, the message envelope, the message header, and the message body. The message header contains control information, including, minimally, an originator's email address and one or more recipient addresses. Usually descriptive information is also added, such as a subject header field and a message submission date/time stamp. Originally a text-only (7-bit ASCII and others) communications medium, email was extended to carry multi-media content attachments, a process standardized in RFC 2045 through 2049. Collectively, these RFCs have come to be called Multipurpose Internet Mail Extensions (MIME).

Electronic mail predates the inception of the Internet and was in fact a crucial tool in creating it, but the history of modern, global Internet email services reaches back to the early ARPANET. Standards for encoding email messages were proposed as early as 1973 (RFC 561). Conversion from ARPANET to the Internet in the early 1980s produced the core of the current services. An email sent in the early 1970s looks quite similar to a basic text message sent on the Internet today.

Network-based email was initially exchanged on the ARPANET in extensions to the File Transfer Protocol (FTP), but is now carried by the Simple Mail Transfer Protocol (SMTP), first published as Internet standard 10 (RFC 821) in 1982. In the process of transporting email messages between systems, SMTP communicates delivery parameters using a message envelope separate from the message (header and body) itself.

TYPE OF ELECTRONIC MAIL

Web-based email (webmail)

This is the type of email that most users are familiar with. Many free email providers host their serves as web-based email (e.g. Hotmail, Yahoo, Gmail, AOL). This allows users to log into the email account by using a web browser to send and receive their email. Its main disadvantage is the need to be connected to the internet while using it. Other software tools exist which integrate parts of the webmail functionality into the OS (e.g. creating messages directly from third party applications via MAPI).

POP3 email services

POP3 is the acronym for Post Office Protocol 3. It is a leading email account type on the Internet. In a POP3 email account, email messages are downloaded to the client device (i.e. a computer) and then they are deleted from the mail server. It is difficult to save and view messages on multiple devices. Also, the messages sent from the computer are not copied to the Sent Items folder on the devices. The messages are deleted from the server to make room for more incoming messages. POP supports simple download-and-delete requirements for access to remote mailboxes (termed maildrop in the POP RFC's). Although most POP clients have an option to leave messages on the server after downloading a copy of them, most e-mail clients using POP3 simply connect, retrieve all messages, store them on the client device as new messages, delete them from the server, and then disconnect. Other protocols, notably IMAP, (Internet Message Access Protocol) provide more complete and complex remote access to typical mailbox operations. Many e-mail clients support POP as well as IMAP to retrieve messages; however, fewer Internet Service Providers (ISPs) support IMAP.

IMAP email servers 

IMAP refers to Internet Message Access Protocol. It is an alternative to the POP3 email. With an IMAP account, a user's account has access to mail folders on the mail server and can use any compatible device to read messages, as long as such a device can access the server. It shows the headers of messages, the sender and the subject and the device needs to request to download specific messages. Usually mail is saved on a mail server, therefore it is safer and it is backed up on an email server.

MAPI email servers 

Messaging Application Programming Interface (MAPI) is a messaging architecture and a Component Object Model based API for Microsoft Windows.