I'm having a somewhat perplexing DNS issue with a only a "few" external domains. Name resolution to external domains works fine with the exception of a few domains (that coincidentally belong to a partner company) that will not resolve from within our internal Network. We're using AD integrated DNS with a Forwarder setup which points to our external DNS server. There are no internal zones created for these problem domains. All other external domains resolve fine. When I perform an nslookup against these domains from inside our network, they time out, but they resolve just fine outside of our network. Shouldn't a name query try the Forwarder and then if it fails, use root hints? I've been able to temporarily resolve the issue by using conditional forwarders, but I'd like to find the root cause. Not sure what else I can do to troubleshoot why only three external domains are not resolving from within our internal network?