I've studied up on this and still don't have a clear understanding, possibly someone here can help. I'm deploying Exchange 2010. Our active directory domain name is atw.local. NetBIOS domain name is atw. DNS suffix is atw.local (if I understand correctly), DNS host name of mail server is mail.atw.local. Very simple active directory domain. With all of this said, my internet domain name is arnoldlaw.net and the A record DNS host name (MX) on the internet will be mail.arnoldlaw.net. The simple question is my environment considered disjoint namesapce? I thnk the internet component is confusing me. Thanks much!

No, disjointed means you have AD domain name attw.local. Then you have a computer in this domain but you configured the computer name as computer1.corp.local. Typically when you join the computer to the domain it will be computer1.attw.local. But you can change the suffix of the computer to computer1.corp.local or whatever suffix you want. That is considered disjointed namespace. It has nothing to do with external DNS. Disjoint Namespace http://technet.microsoft.com/fr-fr/library/cc773264(WS.10).aspxJames Chong MCITP | EA | EMA; MCSE | M+, S+ Security+, Project+, ITIL msexchangetips.blogspot.com

Your Microsoft domain has nothing to do with your MX record.

Hi rediewald, James is right. A disjoint namespace scenario is one in which the primary DNS suffix of a computer does not match the DNS domain name where the computer resides. Thanks, EvanPlease remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.