I have seen this many times, but have not taken the time to troubleshoot before nowJ
I have often heard from customers that they have problems to send e-mails and web browsing to domains like .co.uk, .cn, and .br (not limited to these domains). This is usually related to DNS, and a clear cache/restart of DNS service on DNS servers fixes this. But the problems are suddenly backJ
When the problem is happening, an nslookup command issued for an affected name will return the error “server failed”. A network trace will show that the DNS server does not send any traffic for such a request to the Internet. No events related to a problem are reported in the DNS Event Log.
In Exchange queues you see that e-mails to those domains are in queue with status 451 4.4.0 DNS query failed. If you try to NSLOOKUP those domains following error is received:
I found this interesting KB http://support.microsoft.com/kb/968372 .
So I created a new group policy and linked it to Domain Controller OU, and created a registry change in group policy preferences. (like shown below).
This solved the problems with lookup the domains.