smtp 550 error

[nazreel]

Customer has called me in as he is getting this error when any user tries to send email using Exchange Server. This has happened since the company replaced the adsl router with a new model. Nothing else (to the best of my knowledge and belief) has changed. I am a complete beginner with this, although I have a good background in general computer work and basic networking, doing troubleshooting etc etc.

If someone can tell me where to start looking here I would be very grateful for any and all help.

Thank you.

I have had a look at other problems on this site but none seem to really fit.

 

[noveyron]

Can you post the full NDR (undeliverable message)

TIA

 

[nazreel]

Thank you.

Customer's actual domain has been replaced by customersdomain for privacy.

Headers:

Microsoft Mail Internet Headers Version 2.0
From: postmaster@customersdomain.co.uk
To: sales@customersdomain.co.uk
Date: Tue, 22 Apr 2008 16:34:35 +0100
MIME-Version: 1.0
Content-Type: multipart/report; report-type=delivery-status;
boundary="9B095B5ADSN=_01C8A48E32123D5C00000001customersdomain.co.uk"
X-DSNContext: 7ce717b1 - 1194 - 00000002 - 00000000
Message-ID: <FRaqbC8wS0000002a@customersdomain.co.uk>
Subject: Delivery Status Notification (Failure)

--9B095B5ADSN=_01C8A48E32123D5C00000001customersdomain.co.uk
Content-Type: text/plain; charset=unicode-1-1-utf-7

--9B095B5ADSN=_01C8A48E32123D5C00000001customersdomain.co.uk
Content-Type: message/delivery-status

--9B095B5ADSN=_01C8A48E32123D5C00000001customersdomain.co.uk
Content-Type: message/rfc822

Subject: testing
MIME-Version: 1.0
Content-Type: multipart/alternative;
boundary="----_=_NextPart_001_01C8A48E.5D975373"
Date: Tue, 22 Apr 2008 16:34:33 +0100
Content-class: urn:content-classes:message
X-MimeOLE: Produced By Microsoft Exchange V6.5.7226.0
Message-ID: <7434C03A04DB674DA6590AC6EF6B1689092C99@server1.trs.local>
X-MS-Has-Attach:
X-MS-TNEF-Correlator:
Thread-Topic: testing
Thread-Index: Acikjl1LBCbX0I9ETB6mB27xTYd4gw==
From: "Sales @customersdomain" <sales@customersdomain.co.uk>
To: <nazreel@nazreel.co.uk>

------_=_NextPart_001_01C8A48E.5D975373
Content-Type: text/plain;
charset="us-ascii"
Content-Transfer-Encoding: quoted-printable

------_=_NextPart_001_01C8A48E.5D975373
Content-Type: text/html;
charset="us-ascii"
Content-Transfer-Encoding: quoted-printable



------_=_NextPart_001_01C8A48E.5D975373--

--9B095B5ADSN=_01C8A48E32123D5C00000001customersdomain.co.uk--

Body of email:

From: System Administrator
Sent: 22 April 2008 16:35
To: Sales @ customersdomain
Subject: Undeliverable:testing

Your message did not reach some or all of the intended recipients.

Subject: testing
Sent: 22/04/2008 16:35

The following recipient(s) could not be reached:

nazreel@nazreel.co.uk on 22/04/2008 16:35
There was a SMTP communication problem with the recipient's email server. Please contact your system administrator.

<customersdomain.co.uk #5.5.0 smtp;550 <nazreel@nazreel.co.uk> No such user here>

Hope this helps.

I went over it today and made some changes which were definitely wrong according to the details on this page:

http://support.microsoft.com/default.aspx/kb/825763

Still no joy. Email above was sent and received after changes were made but is identical to previous.

Thank you all.