I use Trend Micro Interscan Messaging Security Suite and Exchange Server 2007. Some people who send e mail to us get returned mail that states: Your message did not reach some or all of the intended recipients. Subject: TEST BACK Sent: 4/22/2008 10:58 AM The following recipient(s) could not be reached: Lana Argomaniz on 4/22/2008 10:58 AM There was a SMTP communication problem with the recipient's email server. Please contact your system administrator. <tsc.republictitle.com #5.5.0 smtp;550-tsc.republictitle.com [207.238.103.14]:61775 is currently not permitted to> This does not happen to everyone who sends mail only some. Does anyone have an idea of what might be happening here?

James, Which version of IMSS are you using ? If your using version 7.0 it can me that the ip-adress is on the black list of the IMSS itself. This is not caused by NRS but by IPP Profiler which blocks ip-adresses if the treshold for some features such as spam, harvesting etc is exceeded. You can check this by opening the IMSS console: IP Filtering > Blocked List although this would cause a 450 or 550. But you please check if the ip-adres is listed there. Regards, Johan

Johan, Thank you for your post, I have been pulling my hair out one strand at a time. I am using version 5.5 which has the feature "network reputation services" which evaluates incoming connections at the IP level before evaluating other message filters. I disabled this feature which did not solve our issue. Turns out our ISP had their DNS records deleted by Network Solutions, which also keeps our DNS. After the problem was corrected, it has taken some time for DNS to propogate throughout the web. That explains why mail is only being received by "some" users. Thanks, James

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