Your message wasn't delivered because of security policies. Microsoft Exchange will not try to redeliver this message for you. Please provide the following diagnostic text to your system administrator

I am receiving this message when attempting to send an email to a craigslist job posting.  I've researched this on the web and found articles that show to remove the 'require that all senders rae authenticated' in the email settings for the sender but still get the same result.

Any ideas?

Reject messages from no senders is also not checked.

Our system is Windows 2003 with Exch 2007.
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It would help if you could post the entire error message details. This would greatly help us determine what you need to do to fix the problem.
creativenetworksAuthor Commented:
Delivery has failed to these recipients or distribution lists:
Your message wasn't delivered because of security policies. Microsoft Exchange will not try to redeliver this message for you. Please provide the following diagnostic text to your system administrator.

The following organization rejected your message:


Sent by Microsoft Exchange Server 2007

Diagnostic information for administrators:

Generating server: #554 5.7.1 <[]>: Client host rejected: Please_use_smtp_relay_of_your_isp_or_setup_non-generic_dns.See:_ xabd-27 ##

Original message headers:

Received: from server.domainname ([]) by
 server.domainname ([]) with mapi; Tue, 23 Mar
 2010 09:55:09 -0700
From: 'email address removed by me'
To: ""
Date: Tue, 23 Mar 2010 09:55:07 -0700
Subject: IT Technician Wanted for SoCal IT Firm (Irvine, CA)
Thread-Topic: IT Technician Wanted for SoCal IT Firm (Irvine, CA)
Thread-Index: AcrKqpJIMSCbE+YJTYaBQSCMwGXojA==
Message-ID: <620856F39EF9A944A83522B81134B816BAD088B566@servername.domainname>
Accept-Language: en-US
Content-Language: en-US
x-cr-puzzleid: {5B617169-84C5-4363-9FC9-324629697376}
x-cr-hashedpuzzle: Ao6Q BWHy C2Fw D/zC EO0O FIIB FbWE FiAu GLNj GsfA HKlK
 Hj5y IEvz Ij5m ItSf
 23 Mar 2010 17:02:08
acceptlanguage: en-US
Content-Type: multipart/alternative;
MIME-Version: 1.0

What to do if your email is being rejected by craigslist email servers
Is your email is being rejected by our servers with a message like this:

 554 5.7.1 <[]>: Client host rejected: please_use_SMTP_relay_of_your_isp,_or_setup_non-generic_dns.

If so, here's the story:
In an effort to curb abuse of our email servers and limit the amount of spam inflicted upon our users, craigslist does not accept email from computers with dynamically assigned IP addresses, or hosts that have generic DNS setup.

If you get the above message, here's what to do:

The easiest solution is to use the mail server of your ISP to relay your email, as they almost certainly have their DNS setup properly in the way we would like. If you're not sure how to setup your mail client to do this, please contact your ISP.
If you have a static IP address and want to be able to send email through your own mail server, you will need to contact your ISP and have them setup non-generic DNS for your IP address.

If these suggestions don't work, some people find it easiest to use one of the many free web based email systems.

What is generic DNS?
When you make a connection to our servers, we use your IP address to perform a reverse lookup to find the name listed for your computer in the domain name service.  We consider you to have generic DNS if the hostname returned contains:

An IP address
The words pool, dhcp, dynamic
The words dsl, ppp, pub
The words server or host
The words dial or dialup
The words cable or modem
The words host or cust/customer
Any other indicators that the hostname is not specific to you or your organization
How do I check for generic DNS?
While the specifics differ by operating system, the basic procedure is the same:

retreive your machine's IP address
perform a DNS query to look up the PTR record for that IP address
Note that you have to specify your IP address for purposes of this query in reverse.  For example, if your IP address is A.B.C.D, you need to look up instead.

Here are some examples using the IP address

Open a command prompt and type the following:

C:\Documents and Settings\username>nslookupDefault Server:      <-------- will be different on your machine, don't panic!Address:                      <-------- same here> set query=ptr>     PTR>
You can see the result of the lookup after the letters PTR above.

Linux, MacOS, other UNIX
Open and type the following into the shell:

$ dig +short$
The results of the lookup are shown immediately after the command.

Still Broken?
If you have a static IP address, run a mail server and do not have generic DNS, and are continuing to run into trouble, please send email to Be sure to include the complete headers, rejection message, and output of your DNS lookup (as shown in the above examples) so that we're able to determine exactly what is happening.


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creativenetworksAuthor Commented:
This worked for us.
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