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electronic mail


(email, e-mail), n. ~ 1. An asynchronous message, especially one following the RFC 2822 or MIME standards, including a header, body, and - optionally - attachments, sent via a computer network held in online accounts to be read or downloaded by the recipients. - 2. A system for transmitting email.


Email is not real-time communication, although delivery time is often minimal. Unlike instant messaging, the sender and recipients do not need simultaneous connections to send or receive email. The header includes information that enables the messages to be delivered and additional metadata to identify, classify, and contextualize the message. The body is often plain or formatted text; it may contain embedded graphics or sound, although not all email readers can properly parse anything beyond plain ASCII. Attachments may be in any format, such as word processing documents, spreadsheets, or media files.

An email system requires an application, sometimes called a mail user agent (MUA), client, or reader, that incorporates a simple text editor used to compose messages and to send and receive messages. The system also requires a mail transport agent (MTA) to store and forward messages. An email system may be implemented on a closed network using proprietary software to exchange messages. However, an email system typically formats messages using the RFC 2822 or MIME standards when the messages are to be exchanged with another system. Email systems commonly transmit messages using the simple mail transport protocol (SMTP). Many MUAs and MTAs are based on the POP3 or IMAP standards to allow interoperability between different systems.

See and 36 CFR 1234.