Electronic mail is hinged around the concept of an address; the
section on Networking Basics made some reference to it while
introducing domains. Your email address provides all of the
information required to get a message to you from anywhere in the
world. An address doesn't necessarily have to go to a human being.
It could be an archive server, {See Archive Servers, for a
description.} a list of people, or even someone's pocket pager.
These cases are the exception to the norm---mail to most addresses is
read by human beings.
%@!.: Symbolic Cacophony
Email addresses usually appear in one of two forms---using the
Internet format which contains @, an "at"-sign, or using the
UUCP format which contains !, an exclamation point, also called
a "bang." The latter of the two, UUCP "bang" paths, is more
restrictive, yet more clearly dictates how the mail will travel.
To reach Jim Morrison on the system south.america.org, one would
address the mail as jm@south.america.org. But if Jim's account was
on a UUCP site named brazil, then his address would be brazil!jm. If
it's possible (and one exists), try to use the Internet form of an
address; bang paths can fail if an intermediate site in the path
happens to be down. There is a growing trend for UUCP sites to
register Internet domain names, to help alleviate the problem of path
failures.
Another symbol that enters the fray is %---it acts as an extra
"routing" method. For example, if the UUCP site dream is connected
to south.america.org, but doesn't have an Internet domain name of its
own, a user debbie on dream can be reached by writing to the address
not smallexample!
debbie%dream@south.america.org
The form is significant. This address says that the local system
should first send the mail to south.america.org. There the address
debbie%dream will turn into debbie@dream, which will hopefully be a
valid address. Then south.america.org will handle getting the mail
to the host dream, where it will be delivered locally to debbie.
All of the intricacies of email addressing methods are fully covered
in the book "!%@@:: A Directory of Electronic Mail Addressing and
Networks" published by O'Reilly and Associates, as part of their
Nutshell Handbook series. It is a must for any active email user.
Write to nuts@ora.com for ordering information.