Have a Windows 2008 domain in native mode with two 2008 domain controllers that function as primary/secondary DNS servers for all internal users/services as well as external services (web/mail/ftp/etc). Internal DNS resolution for all internal clients for internal services occur correctly with no problem. External DNS resolution for all internal clients such as web browsing also occur correctly and consistently. The problem is with our mail server (Exchange 2003 standard) located within the internal network and using these DNS servers for its external resolutions. 99% of all external NS and MX records for the purpose of outbound SMTP mail is resolved, obtained, and cached successfully by the internal DNS servers. However, there is this intermittent problem for domains that for some reason cannot be resolved at times (other times they resolve just fine). During this time (when users receive Exchange delivery delay messages), I can use nslookup to obtain the NS and MX records if I manually connect to other internet DNS servers but not if I connect to our internal DNS server. During this time I get either request time out or no response received from server although there is no problem resolving any other host/MX during that time. The only immediate resolution to this while this occurs is to clear the DNS cache on our DNS server. Immediately after clearing the DNS cache, the MX and NS for the records that wouldn't resolve just moments before would now resolve correctly and the email would be able to go out successfully.
Any ideas - pointers? TIA ~ Finally, powerful endpoint security that ISN'T a resource hog! ~ ~ <http://www.sunbeltsoftware.com/Business/VIPRE-Enterprise/> ~
