petroleumman   0 pts.  |   Dec 11 2006  10:46AM GMT

Hello,

Unfortunatley this is not one of those cut and dry errors with a single cause and solution. This error can be generated because of a number of reasons. That said, let’s look at your scenario, new install. Possibly you overlooked some basic security measures during configuration which may have resulted in your server being blacklisted. Check the following settings to confirm your server is not an open relay; Open Exchange System Manager and navigate to your smtp virtual servers properties. Click the access tab and then relay. Confirm you have placed a check in the box “Allow all computers which successfully authenticate to relay regardless of the list above”. Leaving this unchecked can result in your server becoming an open relay. This is a sure fire way to quickly get blacklisted!

You confirm that you have your server properly locked down and have checked the blacklist status of your server  <a href="http://www.spews.org" title="http://www.spews.(" target="_blank">www.spews.org</a> amongst others can help)check that you have an SPF (sender policy framwork) record set up on your external DNS. This type of record is quickly becoming a requirement with newer mail organizations. What it does essentially is confirm that you are who you say you are to another mail server. Many organizations such as Yahoo, MSN, Hotmail etc. are now starting to require this type of record as a means of thwarting spam. Not having this record could result in your error. If not the cause, having this record listed with your external DNS is a good thing as it may save some headaches down the road.

Everything is clean to this point? Now look at how your mail is sent. Do you relay through an ISP? Use a Smarthost? Have an antivirus application running etc.? Any of these could be the source of the error. Try turning off any that apply one by one and test. If the problem goes away with any one of these then you’ve started to narrow down the culprit. Contact your Smarthost provider, ISP or AV vendor for assistance. Depending on the vendor, you may need to push them to help, but persistance will prevail.

We had a personal experience with this error at our company when sending mail to Hotmail accounts and after several days of trial and error found the culprit to be with our Symantec corporate AV solution. Upgrading to the latest version which had some bug fixes for Exchange helped resolve the issue.

As for Exchange server’s mail filters, these are all good tools to help keep control the flow of and/or the source of inbound mail to your server but have no affect on what your sending out. It’s outbound mail that is responsible for the NDR’s.

Hopefully some of this will help you out.

Good luck!