Not many Microsoft Exchange Server 5.5 customers have migrated yet to Exchange 2000 Server—current estimates place the number at 15 to 20 percent. There probably are many reasons for this slow adoption rate, but one of the main ones is all the prerequisites to migrating to Exchange 2000. One of the questions I'm asked most often is "What do I need to do before migrating to Exchange 2000?" Microsoft Product Support Services (PSS) also lists migration as one of its top Exchange 2000 support issues. This week, I want to give you the top 5 prerequisites for upgrading from Exchange 5.5 to Exchange 2000. If you're getting ready to make the move, meet these criteria before you get too involved.

Prerequisite #1: Stabilize Your Environment
First and foremost, you need to clean up your Exchange 5.5 environment. Take some time to ensure that all your Exchange 5.5 servers run at least Service Pack 3. SP3 contains some important updates and fixes (such as proper Lightweight Directory Access Protocol—LDAP—support, which Exchange needs to interoperate with Windows 2000 Active Directory—AD) that are necessary for your migration. Also ensure that your accounts and mailboxes are ready for migration. For example, if a Windows NT account is associated with multiple mailboxes (resource mailbox scenario), you need to narrow these mailboxes down to one mailbox before you migrate. (This necessity relates to Active Directory Connector—ADC—replication limitations between Exchange 5.5 and Win2K AD.) Other Exchange 5.5 clean-up issues involve public folders and distribution lists (DLs). The important point is to get your Exchange 5.5 environment into a stable and supportable state before you proceed with migration.

Prerequisite #2: Deploy Win2K AD
Before you migrate to Exchange 2000, you must deploy your Win2K AD infrastructure, including DNS. Exchange 2000 simply won't work without both AD and DNS in place. Does this mean that you must completely convert your infrastructure to Win2K before you can install Exchange 2000? Not necessarily, but you must have a minimal AD deployment available for Exchange 2000. DNS is equally important because Win2K, AD, and Exchange 2000 rely heavily on this service. Taking a look at your infrastructure won't be trivial, and rolling out even a minimal Win2K AD service might trigger a domino effect that could cause issues with other infrastructure components. At my company, Win2K AD deployment triggered myriad other projects that we deemed critical to supporting our AD and Exchange 2000 deployment projects.

Prerequisite #3: Understand the ADC
Microsoft developed a little component called the ADC, but the ADC is no little thing as far as its importance to an Exchange 2000 migration. The ADC must synchronize all your Exchange 5.5 mailboxes (i.e., Exchange 5.5 directory objects) with Win2K AD for the two environments to interoperate during the migration. In addition, the ADC provides a method to populate AD. The ADC also plays a key role in the migration of your NT 4.0 user accounts to AD. Proper understanding and deployment of the ADC is a crucial prerequisite to Exchange 2000 migration.

Prerequisite #4: Prepare Your Forest and Domain
Win2K domain and forest preparation involves several tasks. First, you need to ensure that you (or your directory folks) have created an account for Exchange 2000 installation or delegated the necessary permissions to an existing account. Second, Exchange 2000 installation performs several steps besides installing software, so you need to understand the Forestprep and Domainprep installation tasks and how to delegate or perform them before you actually install Exchange 2000. (For more details, see my Exchange UPDATE article, "ForestPrep and DomainPrep: A Crucial Part of Exchange Deployment," http://exchangeadmin.com , InstantDoc ID 23736.) The important point is to plan and coordinate your forest- and domain-preparation activities so that you don't end up trying to figure out these steps while you install your first Exchange 2000 server.

Prerequisite #5: Plan and Test
Plan, test, review, and test again! Before you proceed down the Exchange 2000 migration path, you must analyze your current Exchange 5.5 environment and have a concrete and well-tested plan for how to get to Exchange 2000. This migration plan should cover everything from how you'll upgrade individual servers to how you'll migrate mailboxes and should include hardware design, disaster recovery, routing-topology design, and other issues. If your plan also includes the consolidation or addition of extra services such as the Instant Messaging (IM) service or Exchange 2000 Conferencing Server, you need to plan and test those services as well. And don't just form a plan—test the planned migration steps in a lab environment. Take the time to thoroughly investigate your options and test your methods.

This Top 5 list only scratches the surface of migration. Don't let it mislead you into thinking that migrating will be easier than you anticipated. Judging from Exchange 2000 migration's top rating as a PSS support issue, too few of us are doing enough to meet these prerequisites. For more information to help you get started with your migration, I suggest the following excellent Microsoft resources:

"Microsoft Exchange 2000 Upgrade Series"

"Active Directory and Exchange, Dependencies and Requirements"

"Exchange 2000 and Active Directory Deployment Considerations"

"Exchange Server 5.5 Interoperability and Migration"

"Migrating Mailboxes from Exchange 5.5 to Exchange 2000"