When an email address is incorrect in some way (the system's name is
wrong, the domain doesn't exist, whatever), the mail system will
bounce the message back to the sender, much the same way that the
Postal Service does when you send a letter to a bad street address.
The message will include the reason for the bounce; a common error is
addressing mail to an account name that doesn't exist. For example,
writing to Lisa Simpson at Widener University's Computer Science
department will fail, because she doesn't have an account. {Though if
she asked, we'd certainly give her one.}
From: Mail Delivery Subsystem <MAILER-DAEMON>
Date: Sat, 25 May 91 16:45:14 -0400
To: mg@gracie.com
Cc: Postmaster@cs.widener.edu
Subject: Returned mail: User unknown
----- Transcript of session follows -----
While talking to cs.widener.edu:
>>> RCPT To:<lsimpson@cs.widener.edu>
<<< 550 <lsimpson@cs.widener.edu>... User unknown
550 lsimpson... User unknown
As you can see, a carbon copy of the message (the Cc: header
entry) was sent to the postmaster of Widener's CS department. The
Postmaster is responsible for maintaining a reliable mail system
on his system. Usually postmasters at sites will attempt to aid you
in getting your mail where it's supposed to go. If a typing error was
made, then try re-sending the message. If you're sure that the
address is correct, contact the postmaster of the site directly and
ask him how to properly address it.
The message also includes the text of the mail, so you don't have to
retype everything you wrote.
----- Unsent message follows -----
Received: by cs.widener.edu id AA06528; Sat, 25 May 91 16:45:14 -0400
Date: Sat, 25 May 91 16:45:14 -0400
From: Matt Groening <mg@gracie.com>
Message-Id: <9105252045.AA06528@gracie.com>
To: lsimpson@cs.widener.edu
Subject: Scripting your future episodes
Reply-To: writing-group@gracie.com
.... verbiage ...
The full text of the message is returned intact, including any headers
that were added. This can be cut out with an editor and fed right
back into the mail system with a proper address, making redelivery a
relatively painless process.