[mailhist-discuss] Definition of email

Thomas Haigh thaigh at computer.org
Mon Jun 4 13:18:56 PDT 2012

As Dave Crocker mentioned, when I was preparing my article on the invention
of email for the Washington Post's website it seemed like a good idea to
attempt a definition of the necessary and sufficient characteristics of an
electronic mail system. This wouldn't attempt to capture the features
present in all or most modern systems, but to pin down the essence of what
we mean by electronic mail.


So the tricky thing was to be as broad as possible while excluding things
like faxes, Twitter, newsgroups, electronic bulletin boards, etc. which
would not generally be thought of as electronic mail. Most of those were
never thought of as electronic mail - the exception being fax, as early
usage (through the 1970s) sometimes did include things like electronically
routed telexes and faxes.


People providing comments during the discussion included Dave Walden, Dave
Croker, Ray Tomlinson, Tom Van Vleck and a couple of historians. However,
the definition is mine and I do remember that Dave Crocker favored a simpler




Electronic mail is a service provided by computer programs to send
unstructured textual messages of about the same length as paper letters from
the account of one user to recipients' personal electronic mailboxes, where
they are stored for later retrieval.

What each phase is doing there and why we need to keep it:


1.      "Electronic mail is a service": puts the stress on the system
itself, not individual computer programs


2.      "provided by computer programs": May not be necessary, I think was
there to focus the definition on computer systems rather than something like


3.      "to send unstructured textual messages": unstructured separates this
from earlier network communication where highly structured data was
exchanged within systems like SAGE. Of course email text can be highly
structured, but any system than can transmit an unstructured textual message
can also transmit a structured one. The reverse is not true. Finally,
"textual" further distinguishes electronic mail from fax, image
transmission, etc.


4.      "of about the same length as paper letters": we went backward and
forward on whether to say instead something like "able to handle messages of
at least 2,000 words" or "of unlimited length." Realistically, any
electronic mail system (particularly an early one) has a limit, but the
point is that it must be large enough to permit transmission of the
equivalent of a long letter. This distinguishes electronic mail from
something like SMS.


5.      "from the account of one user": electronic mail always has a single
sender (whether or not the sender is identified to the recipient) and comes
from an account rather than a human (though accounts are often personal).
Also, someone needs an account to send a message, whereas with paper mail
she only need a stamp.


6.      "to recipients' personal electronic mailboxes": we thought about
saying private or secure, but in reality they aren't always. However, the
message does go to the mailbox of one or more recipients and is shown only
to them. This distinguishes electronic mail from something like a post to a
bulletin board which can be seen by all users.


7.      "where they are stored for later retrieval." i.e. asynchronous,
which separates electronic mail from chat.


The definition would include private message functions within conferencing
systems, which I think is perfectly reasonable - they're basically
electronic mail capabilities within a larger system.


Finally, though we did not say it explicitly here, we follow almost everyone
else in the world by treating email and e-mail as contractions of electronic
mail with the same meaning.



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