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Bounced Mail

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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.(5) invisible.xbm

 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. invisible.xbm

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.

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