Planning Your Deployment Path


Topic Last Modified: 2005-07-07

This topic will help you plan your deployment path for Exchange 2003. It is primarily geared toward organizations that have no e-mail infrastructure or who have older versions of Exchange. If you are coming from a non-Microsoft e-mail system such as Lotus Notes or Novell GroupWise, see the Exchange Server 2003 Interoperability and Migration Guide (

The most appropriate path for deploying Microsoft® Exchange Server 2003 depends on an organization's current e-mail infrastructure. For example upgrading from an existing Exchange 2000 organization is a relatively simple process. However, migrating from an Exchange 5.5 organization to Exchange 2003 entails some additional planning because you need to migrate directory information to the Microsoft Active Directory® directory service and messaging system data to Exchange 2003.

In general, smaller companies may be less concerned about the time it takes to deploy Exchange 2003. However, in larger companies where it is not feasible to upgrade all locations at one time, deployment may take from a few weeks to years.

An Exchange 2003 organization can operate in two modes: native mode and mixed mode. Native mode offers full Exchange 2003 functionality, but mixed mode offers interoperability with Exchange 5.5. When you install Exchange 2003, your Exchange organization is in mixed mode by default. This default setting ensures future interoperability with Exchange 5.5.

Native mode in Exchange 2003 is essentially the same as native mode in Exchange 2000. The presence of Exchange 5.5 servers is what determines whether you can run in native mode. Thus, if your organization contains a mixture of both Exchange 2000 and Exchange 2003 servers but no Exchange 5.5 servers, you can switch the Exchange organization to native mode. For more information about the benefits of switching to native mode see "Understanding Mixed and Native Modes."

Your goal should be to minimize the period of coexistence between Exchange 5.5 servers and Exchange 2003 servers so you can take full advantage of Exchange 2003 features. Remember that after you switch an Exchange 2003 organization from mixed mode to native mode, the organization is no longer interoperable with Exchange 5.5 systems. Exchange organizations operating in native mode can contain Exchange 2003 and Microsoft Exchange 2000 servers. You can switch an Exchange organization to native mode only when all of the Exchange servers in it are running Exchange 2003 or Exchange 2000.

Review the requirements in "Understanding Mixed and Native Modes"in the section titled "Are you a candidate for switching to native mode?" Determine when in the project plan all of the requirements will be met, and plan to switch your Exchange organization to native mode at that time.

After you switch from mixed mode to native mode, the change cannot be reversed, and the organization is no longer interoperable with Exchange 5.5 systems. For more information about how to switch to native mode, see "How to Switch to Native Mode."

Every Exchange organization is different, but most should fall under one of the following scenarios. Each scenario has different considerations to think about as you plan your deployment. Some are simple and others are more complex. Select the scenario that best describes your Exchange organization.




You have no e-mail servers.

Planning a New Exchange 2003 Organization

You only have Exchange 2000 servers.

Planning an Upgrade from Exchange 2000

You only have Exchange 5.5 servers

Planning to Move from Exchange 5.5 to Exchange 2003

You have Exchange 2000 and Exchange 5.5 coexisting in mixed mode.

Planning to Move from Mixed Mode Exchange 5.5 and Exchange 2000 to Exchange 2003

You will be deploying Exchange in multiple forests

Planning to Deploy Exchange in a Multiple Forest Environment

You have non-Exchange mail systems.

"Understanding Interoperability and Migration" in Exchange Server 2003 Interoperability and Migration Guide