I just got a client that has a SBS 2011 server that uses Exchange to deliver email to his company. I am not familiar with SBS so I'm not sure how it should be configured. The problem is that there are certain domains that exchange can not send to, they always sit in the queue and retry. I am pretty sure it is a DNS problem, because just as a test, I changed the NIC's dns from localhost to an outside dns server and all the mail was processed, and everyone got their messages. I also ran some nslookups and those particular domains failed to resolve until I changed the NIC dns. I put the dns back to what it was and it all works as it has in the past. What is odd is that those domains USED to resolve. It has only been in the last 6 months that they haven't worked anymore.
But I have heard that SBS is very picky and so I need to know how I should configure its dns to be able to resolve these domains, and not to have to bypass it with the NIC dns.