Simon, thanks for the reply. Our AV software does not allow computers to connect via port 25 with any other host.
Will hopefully get off the list today. Thanks ----- Original Message ----- From: "Simon Butler" <si...@sembee.co.uk> To: "MS-Exchange Admin Issues" <exchangelist@lyris.sunbelt-software.com> Sent: Monday, May 10, 2010 10:09:25 AM GMT -06:00 US/Canada Central Subject: RE: Denied By Policy 550 Turning off NDRs on your own system isn’t likely to help. The problem is with how the original recipients of the email was setup. This usually comes down to one of two things. 1. Rejecting email as spam after delivery – usually because the email is flagged as spam based on content. If the email is spam, then don’t NDR it, drop it. Sending back an NDR to spam after delivery is a waste of time because all spam is spoofed. 2. Accepting email for all users, then NDR the non-existent users, rather than rejecting it at the point of delivery. During the last major email worm outbreak the biggest problem wasn’t the infected messages, but the NDRs that were being sent around by misconfigured servers. Some major antispam appliance vendors are configured to NDR spam based on content by default! If the user concerned received large numbers of NDRs then their email address was used as the spoofed address. Not a massive amount that you can do about it other than sweat it out. My instinct is that you have a BOT inside and it has sent an email to one of the email addresses that the blacklist concerned operates. Simon. -- Simon Butler MVP: Exchange, MCSE Sembee Ltd. e: si...@sembee.co.uk w: http://www.sembee.co.uk/ w: http://www.amset.info/ w: http://blog.sembee.co.uk/ Need cheap certificates for Exchange, compatible with Windows Mobile 5.0? http://CertificatesForExchange.com/ for certificates from just $23.99. Need a domain for your certificate? http://DomainsForExchange.net/ Exchange Resources: http://exbpa.com/ From: bzalew...@comcast.net [mailto:bzalew...@comcast.net] Sent: 10 May 2010 15:14 To: MS-Exchange Admin Issues Subject: Re: Denied By Policy 550 I was reading about that this weekend. So the only way to stop this is to stop sending NDR's? And of course that will block legitimate NDR's as well. So we are really stuck and just have to watch this and the RBL's to make sure we get off ASAP. Thanks for the help ----- Original Message ----- From: "Michael B. Smith" <mich...@smithcons.com> To: "MS-Exchange Admin Issues" <exchangelist@lyris.sunbelt-software.com> Sent: Monday, May 10, 2010 9:09:24 AM GMT -06:00 US/Canada Central Subject: RE: Denied By Policy 550 Yes. Google “back scatter”. Stop sending NDRs, unfortunately. Regards, Michael B. Smith Consultant and Exchange MVP http://TheEssentialExchange.com From: bzalew...@comcast.net [mailto:bzalew...@comcast.net] Sent: Monday, May 10, 2010 10:06 AM To: MS-Exchange Admin Issues Subject: Re: Denied By Policy 550 I believe this started last week when a users was receiving thousands of NDR reports on email she did not send. As far as we know it was not her PC causing the issue. We removed all the message from the queue on the Exchange server and the messages stopped. Could this have been caused by a user that had her in the address book and they had a virus on their computer? ----- Original Message ----- From: "N Parr" <npar...@mortonind.com> To: "MS-Exchange Admin Issues" <exchangelist@lyris.sunbelt-software.com> Sent: Monday, May 10, 2010 8:41:11 AM GMT -06:00 US/Canada Central Subject: RE: Denied By Policy 550 For future reference check out dnsstuff.com RBL Alert service. It will watch the major RBL's and alert you if any of your sending IP's show up. Gives you a heads up to hopefully fix the problem or get yourself removed. From: Eric Wittersheim [mailto:ewittersh...@aasmnet.org] Sent: Monday, May 10, 2010 8:37 AM To: MS-Exchange Admin Issues Subject: RE: Denied By Policy 550 Google RBL check. From: bzalew...@comcast.net [mailto:bzalew...@comcast.net] Sent: Monday, May 10, 2010 8:34 AM To: MS-Exchange Admin Issues Subject: Re: Denied By Policy 550 What is the easist way to determine the list you are on? ----- Original Message ----- From: "Michael B. Smith" <mich...@smithcons.com> To: "MS-Exchange Admin Issues" <exchangelist@lyris.sunbelt-software.com> Sent: Monday, May 10, 2010 8:31:01 AM GMT -06:00 US/Canada Central Subject: RE: Denied By Policy 550 Almost certainly. Regards, Michael B. Smith Consultant and Exchange MVP http://TheEssentialExchange.com -----Original Message----- From: Brent Zalewski [mailto:bzalew...@comcast.net] Sent: Monday, May 10, 2010 9:30 AM To: MS-Exchange Admin Issues Subject: Denied By Policy 550 We have an Exchange 2007 SP1 server. We have had several users send messages to Internet email addresses and have an NDR come back with the following: block.microcomps.com #550 Denied by policy ## dsmdc-mail-bxga2 #550 Denied by policy Is this from some RBL? Thanks Brent
