I'm running into a problem at one of our clients. W2K3 AD, running E2K3. When SMTP mail goes out, we're seeing DNS problems that result in NDRs. This type of problem has been documented here: http://social.technet.microsoft.com/forums/en-US/exchangesvrtransport/thread /178b88bb-bbdb-4cc2-896b-711fdeeb36d8/
Bottom line is that DNS lookups are failing, and mail is going to the A record for the remote domain instead of the MX record. Apparently this is by design with E2K3/W2K3 when a negative reply comes back. What I'm trying to find out is this: Is there a way to prevent server-side caching of negative replies to remote DNS queries? Or at least reduce their life to a few seconds? I've seen articles that show how to do it for the client side, but that doesn't affect the DNS server cache. We're using ISP forwarders (ATT). I think there may be a firewall (watchguard) or other external issue causing the DNS lookup failures. I'm trying to get the client to authorize that kind of troubleshooting, but in the meantime, we're looking for a fix from another angle. Right now, I've created an AT job to clear the DNS server cache every 5 minutes. That's an ugly workaround, but when the CEO gets NDRs, you get creative. :-) Any ideas? Thanks... *********************** Charlie Kaiser [email protected] Kingman, AZ *********************** ~ Finally, powerful endpoint security that ISN'T a resource hog! ~ ~ <http://www.sunbeltsoftware.com/Business/VIPRE-Enterprise/> ~
