We want to deploy Outlook Mobile Access (OMA), but we aren't yet ready to move all of our Exchange 2000 Server systems to Exchange Server 2003. Is it possible for users of both Exchange versions to use OMA 2003?

Yes, both Exchange versions can use OMA 2003, although you'll still have to upgrade (or install) at least one server running Exchange 2003. Here's what you need to do:

1.Run Exchange 2003 ForestPrep and DomainPrep in your Active Directory (AD) forest. This step is necessary to obtain the AD schema extensions on which OMA depends.

2.If you're using front-end servers, upgrade them to Exchange 2003. If you don't want to upgrade all your front-end servers, you'll need to limit your OMA users to the servers you do upgrade.

3.Introduce an Exchange 2003 server, either through an in-place upgrade of an existing server or through the installation of a new server. The only requirement is that the server be in your Exchange organization.

4.Move all mailboxes that you want to make available through OMA to the Exchange 2003 server.

5.Expose OMA to the Internet, preferably by publishing it through Microsoft Internet Security and Acceleration (ISA) Server or a comparable firewall product.