Source : WordNet®

electronic mail
     n : (computer science) a system of world-wide electronic
         communication in which a computer user can compose a
         message at one terminal that is generated at the
         recipient's terminal when he logs in [syn: {e-mail}, {email}]
         [ant: {snail mail}, {snail mail}, {snail mail}]

Source : Free On-Line Dictionary of Computing

electronic mail
     
         (e-mail) Messages automatically passed from one
        computer user to another, often through computer {networks}
        and/or via {modems} over telephone lines.
     
        A message, especially one following the common {RFC 822}
        {standard}, begins with several lines of {headers}, followed
        by a blank line, and the body of the message.  An increasing
        number of e-mail systems support the {MIME} {standard} which
        allows the message body to contain "{attachments}" of
        different kinds rather than just one block of plain {ASCII}
        text.  It is conventional for the body to end with a
        {signature}.
     
        Headers give the name and {electronic mail address} of the
        sender and recipient(s), the time and date when it was sent
        and a subject.  There are many other headers which may get
        added by different {message handling systems} during delivery.
     
        The message is "composed" by the sender, usuallya using a
        special program - a "{Mail User Agent}" (MUA).  It is then
        passed to some kind of "{Message Transfer Agent}" (MTA) - a
        program which is responsible for either delivering the message
        locally or passing it to another MTA, often on another {host}.
        MTAs on different hosts on a network often communicate using
        {SMTP}.  The message is eventually delivered to the
        recipient's {mailbox} - normally a file on his computer - from
        where he can read it using a mail reading program (which may
        or may not be the same {MUA} as used by the sender).
     
        Contrast {snail-mail}, {paper-net}, {voice-net}.
     
        The form "email" is also common, but is less suggestive of the
        correct pronunciation and derivation than "e-mail".  The word
        is used as a noun for the concept ("Isn't e-mail great?", "Are
        you on e-mail?"), a collection of (unread) messages ("I spent
        all night reading my e-mail"), and as a verb meaining "to send
        (something in) an e-mail message" ("I'll e-mail you (my
        report)").  The use of "an e-mail" as a count noun for an
        e-mail message, and plural "e-mails", is now (2000) also well
        established despite the fact that "mail" is definitely a mass
        noun.
     
        Oddly enough, the word "emailed" is actually listed in the
        Oxford English Dictionary.  It means "embossed (with a raised
        pattern) or arranged in a net work".  A use from 1480 is
        given.  The word is derived from French "emmailleure",
        network.  Also "email" is German for enamel.
     
        {The story of the first e-mail message
        (http://www.pretext.com/mar98/features/story2.htm)}.
     
        (2002-07-14)