Email Addresses Posted by Onlinepublications , Monday, March 29, 2010 at 10:48 PM, in Labels: Email Addresses

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, 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:

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.

Sending and Receiving Mail

We'll make one quick diversion from being OS-neuter here, to show you what it will look like to send and receive a mail message on a Unix system. Check with your system administrator for specific instructions related to mail at your site.

A person sending the author mail would probably do something like this:

     % mail brendan@cs.widener.edu Subject: print job's stuck

     I typed 'print babe.gif' and it didn't work! Why?? 

 The next time the author checked his mail he would see it listed in his mailbox as: 

 % mail "/usr/spool/mail/brendan": 1 messages 1 new 1 unread

 U  1 joeuser@foo.widene Tue May  5 20:36   29/956   print job's stuck ?

which gives information on th sender of the email, when it was sent, and the subject of the message. He would
probably use the 'reply' command of Unix mail to send this response:
     ? r
     To: joeuser@foo.widener.edu
     Subject: Re: print job's stuck
 
     You shouldn't print binary files like GIFs to a printer!
     Brendan
Try sending yourself mail a few times, to get used to your system's mailer. It'll save a lot of wasted aspirin
for both you and your system administrator.