Bounce message every 67 minutes

Hi,

I am running Postfix 2.1.1. I am having a problem with bounce messages,
as I am getting the following message every 67 minutes now:

This is the Postfix program at host mail.summerleaze.co.uk.

I'm sorry to have to inform you that your message could not be
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 Postfix program

<test@234dlclkjc.com>: Host or domain name not found. Name service error for
name=234dlclkjc.com type=A: Host not found



Reporting-MTA: dns; mail.summerleaze.co.uk
X-Postfix-Queue-ID: 8D6B79256B
X-Postfix-Sender: rfc822; nicke@re-gen.co.uk
Arrival-Date: Fri, 15 Oct 2004 11:44:22 +0100 (BST)

Final-Recipient: rfc822; test@234dlclkjc.com
Action: failed
Status: 5.0.0
Diagnostic-Code: X-Postfix; Host or domain name not found. Name service
error
for name=234dlclkjc.com type=A: Host not found



Subject:
This is a deliberate test for postfix bounce
From:
Nick Edwards <nicke@re-gen.co.uk>
Date:
Fri, 15 Oct 2004 11:44:21 +0100
To:
test@234dlclkjc.com

I have searched on the net and cannot find anything to sort this out.
Other users alerted me to this.

Any help would be appreciated.

Nick