Is there any particularity when myAD DS Domain name is type "mybusiness.local" when installing Exchange Srvr 2007 SP1 on Win Svr 2008?and,When I'm configuring my DNS server, the fully DNS name of my domain must be "mybusines.local" or "mybusiness.local." (finished in dot)? Thank you very much.

The only issue I am aware of with the .local domian name is if you try to access resources from a Mac OS.http://support.microsoft.com/default.aspx/kb/836413(Obviously I assuming you have external validSMTP addresses to use and will assign those into your Ex organisation when built)

Per my research, theres no issue to use .local except the one as AE1971 suggested Other Resource: To use a .Local or real internet DNS name

I agree with both comments above. There are no known issues except the one linked above. For the other part of your question, while configuring the DNS server or any of the zones there, you dont really need to add . (period) after the domain name. That last period is always presumed and does not require to be added necessarily and that is how it operates on internet as well.MMilind Naphade | MCTS:M | http://www.msexchangegeek.com