Scenario: We have two parts to our organization, corporate office and public relations. We are beginning to setup our Exchange organization and have a couple configuration issues that we would like to get input on. We have not decided which version to use yet, 2003 or 2007, but we will be in an AD 2003 domain operating most likely in mixed mode. Current AD design is to have a single forest with mutliple domains, a place holder domain and a user domain. One of design tasks is to create and Exchange organization that will service both corporate and public parts of the organization and that if the servers handling the corporate side need to be taken down for maintenance that it does not impact the public side. I wanted to know the best way to set that up. Scenarios: Multiple Exchange servers in a clustered environment with two information stores, one for corporate and one for public. If we loose one Exchange server, there are still servers to handle requests and if we need to take down the corporate information store, the public store remains online. Is this a good plan? Or should we just create multiple administrator groups and have the corporate store under one and the public store under the other? What would be the advantage disadvantage between the two scenarios? If anyone can provide any ideas or solutions on how we should configure this, that would be greatly appreciated. thanks.

Definitely go to Exchange 2007, skipping 2003. You will not regret it, as Exchange 2007 is more scalable, flexible, reliable, etc Assuming you go with Exchange 2007, here are my comments: You said AD will be running in mixed mode, but I should point out that is not possible: The ActiveDirectory domain functional level must be Windows2000Server-native or higher for all domains in the ActiveDirectory forest where you will install Exchange2007" Additionally, "The Exchange organization has been converted to native mode" http://technet.microsoft.com/en-us/library/bb125239(EXCHG.80).aspx Now, as to your suggested plan: The 2nd scenario is also impossible, as there are no more administrative groups in Exchange 2007. This is a legacy concept that was replaced with using the AD structure to better define administration. The 1st option is feasible, and isnt a bad thought, but I would ask more about your environment before I suggest any particular path. Specifically, how many users in each part? If you have a large numbers of users, or the users have lots of mail, you might want multiple storage groups for each part anyway. Exchange 2007 supports up to 50 databases, but suggests that each database is 100GB or less.