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Understanding Common Mail Errors

As a user trying to deal with the E-mail administrator, one useful thing to do is to actually read through bounce notices when you receive them. This practice not only lets you understand what's going on better, but helps you to send an informed E-mail that speeds up the technical support process—or avoid paging your administrator frantically for something that doesn't actually need her intervention.

Suppose you see text such as this:

**********************************************
** THIS IS A WARNING MESSAGE ONLY **
** YOU DO NOT NEED TO RESEND YOUR MESSAGE **
**********************************************

The original message was received at Fri, 05 Mar 2004 19:29:27 -0600
from mail.example.net [192.168.1.50]

----- The following addresses had transient non-fatal errors -----
<user@example.net>

----- Transcript of session follows -----
<user@example.net>... Deferred: Connection refused by mail.example.com.
Warning: message still undelivered after 14 hours
Will keep trying until message is 5 days old

You don't need to do anything; there could be just a temporary glitch in the system and the MTAs will continue trying to deliver the mail. However, you may see something similar to this instead:

The original message was received at Tue, 13 Jan 2004 14:12:29 -0700
from mail.example.net [192.168.1.50]

----- The following addresses had permanent fatal errors -----
<user@example.com>
----- Transcript of session follows -----
... while talking to mail.example.net.:
>>> RCPT To:<user@example.com>
<<< 550 <user@example.com>... user unknown
550 <user@example.com>... user unknown

You probably just mistyped the E-mail address. Sometimes you'll see this response if a virus is forging your E-mail address and trying to blast out E-mail to everyone and their dog.

If someone's mailbox at the MDA is full, the following response may be returned to you:

The original message was received at Tue, 1 Feb 2004 15:23:21 -0800
from [192.168.4.15]

----- The following addresses had permanent fatal errors -----
<user@example.net>
  (reason: Mailbox Full )

----- Transcript of session follows -----
maildrop: maildir over quota.

And now, the one that tends to confuse people most: If you tried sending E-mail to someone but your server is blocked for whatever reason by a DNSBL, among the text in the bounce E-mail there will be a Reason: field, with terms such as rejected or refused, sometimes with an explanation and often even a URL to the particular DNSBL that blocked your message. These responses are handy to send to your E-mail administrator so he or she knows who to contact to solve the problem.

When you need to share a genuine problem with your E-mail administrator, be sure to forward the entire E-mail, including the headers, so the administrator can see the full error message.

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