E-mail, or email, is short for "electronic mail" and refers to composing, sending, and receiving messages over electronic communication systems. Most e-mail systems today use the Internet, and e-mail is the most popular use of the Internet.
An internet E-mail address is a string of the form [email protected]. It should be readed as "jsmith at corporation.com". The first part is the username of the person, and the second part is the hostname of the computer in which that person has an e-mail account. On the early days of the internet, e-mail addresses had to also include the "route" of the message, that is, a path between the computer of the sender and the computer of the receivers. Nowadays, these routes are calculated automatically based on DNS MX records.
The format of internet e-mail messages is defined in RFC 2822. Prior to the introduction of RFC 2822 the format was described by RFC 822.
Internet e-mail messages usually have at least four fields:
- From - The e-mail address of the sender of the message
- To - The e-mail address of the receiver of the message
- Subject - A brief summary of the contents of the message
- Body - The message itself, usually containing a Signature block at the end
Other fields include:
- Cc - Carbon copy (because typewriters used carbon film to copy what was written on them.
- Bcc - Blind carbon copy (the recipient of this copy will know who was in the To: field, but the To:-recipients cannot see who is on the BCC: list)
- Attachments - Files that complement the message
- Date - Date in which the e-mail was sent
- Content-Type - Information about how the message has to be displayed, usually a MIME type.
Messages are exchanged between hosts using the Simple Mail Transfer Protocol with software like Sendmail. Users download their messages from servers usually with either the POP or IMAP protocols.
Social issues about e-mail: Netiquette, Internet humor, Internet slang, spam, virus.