An error message from Computer Solution's email delivery subsystem (mailer-daemon) indicates that there was a problem in delivering your message to its destination. When you receive an error from our mail system, your message will be returned to you along with an outline of the mail delivery problem.

This document will help you become more familiar with the format and content of our mailer-daemon error messages so you can identify delivery problems and possibly correct the situation.

• 550 MAILBOX NOT FOUND

This error indicates that the address no longer exists or the email address is mis-spelled.

• 550 SENDER DOMAIN NOT FOUND IN DNS
• 550 REQUESTED ACTION NOT TAKEN: DNS FAILURE

These errors indicate that there are DNS resolution problems somewhere between their domain and us. This usually means that Computer Solutions is unable to resolve their domain name in DNS before accepting that mail for delivery.   This might be because their DNS servers are offline (in which case try again later, or give us an email so we can troubleshoot for you), or you made a typo.  Doublecheck to ensure that you haven't misspelt the domain name.

• 552 MAILBOX FULL

This error indicates that the recipients mailbox is full. They  will have to free some space in the mailbox before additional email can be received.

• 552 MESSAGE EXCEEDS MAXIMUM FIXED SIZE

This indicates that the mail sent was larger than their system currently allows. This includes the message text, headers and the attachment combined. We have no control over 3rd party servers - most servers have limits of around 5M, although we've seen servers with 1M limits. Try send the message again without the attachment, asking them what the maximum size attachment they can receive is.

Now you've learnt why, we'll examine some common bounce messages and the reasons why they bounced.

Example 1:  

> Hi. This is the qmail-send program at mail.shanghaiguide.com.cn.
> I'm afraid I wasn't able to deliver your message to the following
> addresses.
> This is a permanent error; I've given up. Sorry it didn't work out.
> 
> <richard.li@erpegy.com>:
> Sorry, I couldn't find any host named erpegy.com. (#5.1.2)

The important details are here - > <richard.li@erpegy.com>:
> Sorry, I couldn't find any host named erpegy.com. (#5.1.2)

What it is saying, is that it couldn't find any domain name called erpegy.com
Usually you'll get this if you have made a spelling mistake in the domain name.



Example 2:

From: MAILER-DAEMON@ms.com (Mail Delivery System)
Subject: Undelivered Mail Returned to Sender
To: XXXX
Auto-Submitted: auto-replied

This is the mail system at host hqvsbh2.ms.com.

I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.

For further assistance, please send mail to <postmaster>

If you do so, please include this problem report. You can
delete your own text from the attached returned message.

                   The mail system

<hani.abuali@msdw.com>: User unknown in virtual alias table

The important details are here - <hani.abuali@msdw.com>: User unknown in virtual alias table

What its saying, is that the email address is not known at that server.
This can be for a number of reasons, such as
- that email address is no longer valid (eg the person has moved companies)
- you made a spelling mistake in the email address.


Example 3:

Hi. This is the qmail-send program at mail.shanghaiguide.com.

I'm afraid I wasn't able to deliver your message to the following addresses.

This is a permanent error; I've given up. Sorry it didn't work out.

 

<really-sorry@best-finance.biz>:

82.103.132.52 does not like recipient.

Remote host said: 550 "Unknown User"

Giving up on 82.103.132.52.

The important details are here - Remote host said: 550 "Unknown User"

In this case its an evil spammer trying to setup an account on our forums, and providing a fake address. 
This is pretty much the same error as in example 2, although its easier to understand.

Example 4:

    This is a slightly different example - this one is one that clients will see if they are listed in any of the spam checks we use.

 

451: Blocked  please visit http://ORDB.org/lookup/?host=X.X.X

or

451 Blocked - see http://www.spamcop.net/bl.shtml?X.X.X

or

451 Mail from X.X.X/24 refused, see http://anti-spam.org.cn/services/rblquery.php?IP=X.X.X

 
The message in question was blocked because it came from a domain or IP address that is currently listed with one of our Spam filters. These filters are utilized to help prevent excessive spamming to our email providers. If your domain or IP address is listed with any of the Spam filters we currently use, your message will not be delivered.
 
If you believe that you have been unfairly added to any or all of these particular lists, please contact the website for the Spam list that has you listed. Contacting us won\'t help you!

 •  Ordb (relays.ordb.org)
 •  Spamcop (bl.spamcop.net)
 •  Osirusoft (socks.relays.osirusoft.com)
 •  Wirehub (blackholes.wirehub.net)
 •  Spamhaus (www.spamhaus.org)
 •  AntiSpam (www.anti-spam.org.cn)

I'll add more examples here as and when we get asked about them.