We run an Exchange 2003 email server which also doubles as a SDC / DNS server. The PDC also serves DNS requests too. Every now and again an email will fail. Where the email is going to or coming from doesn't seem to make much difference as long as it passes through our organization but when it fails it sends an NDR saying,
"The destination server for this recipient could not be found in Domain Name Service (DNS). Please verify the email address and retry. If that fails, contact your administrator. "
McAfee's VirusScan Enterprise is running on the Exchange server. It had logged the following error:
Blocked by port blocking rule C:\WINDOWS\System32\dns.exe Anti-virus Standard Protection:Prevent IRC communication 10.0.0.6:6668
The antivirus log times somewhat match up with the failed email times. I've re-configured this particular AV rule and I'm hopeful that it will do the trick. Is there a simple way to test this?
Also worthy of note, this exchange server is scheduled for some maintenance. It has been running straight for almost 2 years now. Could this be causing issues? Other than the random DNS NDR here and there performance and delivery are both quite fast.
So, I'm asking for help in testing the configuration change I have made and whether other people have encountered this NDR for other reasons which might apply to myself.
Thanks in advance.