INTERNET EMAIL ADDRESSING EXPLAINED

So now you're ready to send e-mail to other people on the Net.  Of
course, you need somebody's address to send them mail.  How do you get 
it?  

Alas, the simplest answer is not what you'd call the most elegant: you 
call them up on the phone or write them a letter on paper and ask them.  
Residents of the electronic frontier are only beginning to develop the 
equivalent of phone books, and the ones that exist today are far from 
complete.

Eventually, you'll start corresponding with people, which means you'll 
want to know how to address mail to them.  It's vital to know how to do 
this, because the smallest mistake -- using a comma when you should have 
used a period, for instance, can bounce the message back to you, 
undelivered.  In this sense, Net addresses are like phone numbers: one 
wrong digit and you get the wrong person.  Fortunately, most net 
addresses now adhere to a relatively easy-to-understand system. 

Sending mail outside of your system, will require the use of the Net
equivalent of area codes, called "domains." A basic Net address will
look something like this: 
 
     tomg@world.std.com 
 
Tomg is somebody's user ID, and he is at (hence the @ sign) a site (or in 
Internetese, a "domain") known as std.com.  Large organizations often 
have more than one computer linked to the Internet; in this case, the 
name of the particular machine is world (you will quickly notice that, 
like boat owners, Internet computer owners always name their machines). 

Domains tell you the name of the organization that runs a given e-mail 
site and what kind of site it is or, if it's not in the U.S., what 
country it's located in.  Large organizations may have more than one 
computer or gateway tied to the Internet, so you'll often see a two-part 
domain name; and sometimes even three- or four-part domain names. 

In general, American addresses end in an organizational suffix, such as 
".edu"  (which means the site is at a college or university). Other 
American suffixes include: 
          
     .com for businesses 
     .org for non-profit organizations 
     .gov and .mil for government and military agencies 
     .net for companies or organizations that run large networks.  
 
Sites in the rest of the world tend to use a two-letter code that 
represents their country.  Most make sense, such as .ca for Canadian 
sites, but there are a couple of seemingly odd ones (at least to 
Americans).  Swiss sites end in .ch, while South African ones end in .za.  
A few U.S. sites have followed this international convention (such as 
nred.reading.ma.us). 

You'll notice that the above addresses are all in lower-case.  Unlike 
almost everything else having anything at all to do with Unix, most Net 
mailing systems don't care about case, so you generally don't have to 
worry about capitalizing e-mail addresses.  Alas, there are a few 
exceptions -- some public-access sites do allow for capital letters in 
user names.  When in doubt, ask the person you want to write to, or let 
her send you a message first (recall how a person's e-mail address is 
usually found on the top of her message). The domain name, the part of 
the address after the @ sign, never has to be capitalized.               

It's all a fairly simple system that works very well, except, again, it's 
vital to get the address exactly right -- just as you have to dial a 
phone number exactly right.  Send a message to tomg@unm.edu (which is the 
University of New Mexico) when you meant to send it to tomg@umn.edu (the 
University of Minnesota), and your letter will either bounce back to you 
undelivered, or go to the wrong person. 

If your message is bounced back to you as undeliverable, you'll get an 
ominous looking-message from MAILER-DAEMON (actually a rather benign Unix 
program that exists to handle mail), with an evil-looking header followed 
by the text of your message. Sometimes, you can tell what went wrong by 
looking at the first few lines of the bounced message.  Besides an 
incorrect address, it's possible your host system does not have the other 
site in the "map" it maintains of other host systems. Or you could be 
trying to send mail to another network, such as Bitnet or CompuServe, 
that has special addressing requirements. 

Sometimes, figuring all this out can prove highly frustrating.  But 
remember the prime Net commandment: Ask.  Send a message to your system 
administrator. Include a copy of the header from the original message.  
He or she might be able to help decipher the problem. 

There is one kind of address that may give your host system particular 
problems.  There are two main ways that Unix systems exchange mail.  One 
is known as UUCP and started out with a different addressing system than 
the rest of the Net.  Most UUCP systems have since switched over to the 
standard Net addressing system, but a few traditional sites still cling 
to their original type, which tends to have lots of exclamation points in 
it, like this: 
 
     uunet!somesite!othersite!mybuddy 
 
The problem for many host sites is that exclamation points (also known as 
"bangs") now mean something special in the more common systems or 
"shells" used to operate many Unix computers. This means that addressing 
mail to such a site (or even responding to a message you received from 
one) could confuse the poor computer to no end and your message never 
gets sent out. If that happens, try putting backslashes in front of each 
exclamation point, so that you get an address that looks like this: 
          
     uunet\!somesite\!othersite\!mybuddy 
 
Note that this means you may not be able to respond to such a message by 
typing a lowercase r  -- you may get an error message and you'll have to 
create a brand-new message.

If you want to get a taste of what's possible on the Net, start a message 
to this address: 

     president@whitehouse.gov

Compose some well wishes (or grumblings, if you're so inclined).  Send 
off the message, and within a few seconds to a few hours (depending on 
the state of your Net connection), you'll get back a reply that your 
message has been received.  If you don't feel like starting at the top, 
send a message instead to 

     vice-president@whitehouse.gov


The "mail" program is actually a very powerful one and a Netwide 
standard, at least on Unix computers.  But it can be hard to figure out -
- you can type a question mark to get a list of commands, but these may 
be of limited use unless you're already familiar with Unix. Fortunately, 
there are a couple of other mail programs that are easier to use. 

