There can be many reasons that e-mail returns to you without being delivered. Normally a message bounces because of human error. To understand why the e-mail has been returned to you, it will help to be able to interpret its header

In the header of the returned message you will see several possible reasons for the e-mail to have been returned. These reasons will be indicated by error messages such as user unknown or host unknown . Both of these errors indicate a problem with the e-mail address to which the message was sent.

If you get the user unknown message, the problem is that the portion of the e-mail address before the @ symbol has been rejected by the recipient's e-mail server. Please check the e-mail address that you sent the message to; you may have mis-typed the address. Otherwise, the e-mail address may have been canceled and is no longer valid. Below is an example of the header of an e-mail message that bounced because of user unknown .


Return-Path: <MAILER-DAEMON>
Date: Thu, 10 Apr 1997 08:59:38 -0400 (EDT)
From: Mail Delivery Subsystem <MAILER-DAEMON@westelcom.com>
To: <support@westelcom.com>
Subject: Returned mail: User unknown
Auto-Submitted: auto-generated (failure)

The original message was received at Thu, 10 Apr 1997 08:59:38 -0400
(EDT) from brickbat9.westelcom.com [207.69.200.12]
-----

The following addresses had permanent fatal errors -----
xxxxxxx@westelcom.com

Notice the very last line, which indicates the address to which the original e-mail was sent. The delivery failed because there is no mailbox with the name xxxxxxx, at Westelcom. The e-mail continues below.


----- Transcript of session follows -----
... while talking to localhost.westelcom.com.:
>>> RCPT To:<xxxxxxx>
<<< 550 xxxxxxx...User unknown
550 <xxxxxxx@westelcom.com>... User
unknown
Reporting-MTA: dns; camel10.westelcom.com
Received-From-MTA: DNS; brickbat9.westelcom.com
Arrival-Date: Thu, 10 Apr 1997 08:59:38 -0400 (EDT)

Final-Recipient: RFC822; xxxxxxx@camel10.westelcom.com
Action: failed
Status: 5.1.1
Remote-MTA: DNS; localhost.westelcom.com
Diagnostic-Code: SMTP; 550 xxxxxxx...User unknown
Last-Attempt-Date: Thu, 10 Apr 1997 08:59:38 -0400 (EDT)
Return-Path: <support@westelcom.com>
Received: from brickbat9.westelcom.com (brickbat9.westelcom.com
[207.69.200.12]) by camel10.westelcom.com (8.8.5/8.8.5)
with ESMTP id IAA32741 for <xxxxxxx@westelcom.com>;
Thu, 10 Apr 1997 08:59:38 -0400 (EDT)
Received: from internal.westelcom.com (bronx.westelcom.com [207.69.183.53])
by brickbat9.westelcom.com (8.8.5/8.8.5) with SMTP id
IAA16526 for <xxxxxxx@westelcom.com>;
Thu, 10 Apr 1997 08:58:37 -0400 (EDT)
Message-Id: <1.5.4.16.19970410120110.218f1288@pop.internal.westelcom.com>
X-Sender: support@pop.internal.westelcom.com
X-Mailer: Windows Eudora Light Version 1.5.4 (16)
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Date: Thu, 10 Apr 1997 08:01:10 -0400
To: xxxxxxx@westelcom.com
From: Support <support@westelcom.com>
Subject: IE 4.0 Beta

If you get the host unknown message, the error is caused by the portion of the e-mail address after the @ symbol. Usually, the e-mail address has been mis-typed; however, there may have been a network problem on the receiving end, at the time you sent the e-mail, which prevented the message from finding the recipient's e-mail server. The example below includes the e-mail header of a message which bounced because the address name was incorrect.


Date: Thu, 10 Apr 1997 08:59:26 -0400 (EDT)
From: Mail Delivery Subsystem <MAILER-DAEMON@westelcom.com>
To: <support@westelcom.com>
Subject: Returned mail: Host unknown (Name server: westel.com:
host not found)

Notice that "westelcom" is misspelled above. If the address is not spelled correctly, the e-mail cannot be delivered. The header continues...


----- The following addresses had permanent fatal
errors -----
<support@westel.com>

----- Transcript of session follows -----
550 <support@westel.com>... Host
unknown (Name server: westel.com: host not found)
Reporting-MTA: dns; brickbat9.westelcom.com
Received-From-MTA: DNS; bronx.westelcom.com
Arrival-Date: Thu, 10 Apr 1997 08:59:25 -0400 (EDT)

Final-Recipient: RFC822; support@westel.com
Action: failed
Status: 5.1.2
Remote-MTA: DNS; westel.com
Last-Attempt-Date: Thu, 10 Apr 1997 08:59:26 -0400 (EDT)
Return-Path: <support@westelcom.com>
Received: from internal.westelcom.com (bronx.westelcom.com [207.69.183.53])
by brickbat9.westelcom.com (8.8.5/8.8.5) with SMTP id
IAA16714 for <support@westel.com>;
Thu, 10 Apr 1997 08:59:25 -0400 (EDT)
Message-Id: <1.5.4.16.19970410120157.218fc8dc@pop.internal.westelcom.com>
X-Sender: support@pop.internal.westelcom.com
X-Mailer: Windows Eudora Light Version 1.5.4 (16)
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Date: Thu, 10 Apr 1997 08:01:57 -0400
To: support@westel.com
From: Support <support@westelcom.com>
Subject: IE 4.0 Beta