Deciding When to Move Users

You can either move your users all at once, a process called single-phase migration, or move them in groups, a process called multi-phase migration. Single- phase migration can be good for your organization if you’re not moving data from your existing system, you have the capability to move everyone at the same time, and you have all the hardware you need to run your Exchange 2003 systems. In larger environments, single-phase migration is the better choice merely because of the resource constraints when moving large numbers of mailboxes, distribution lists, and other Exchange information in a single effort.

The multi-phase migration is better when your organization cannot upgrade all departments at the same time, you need to free up hardware for redeployment during the latter stages of the migration, or your organization can’t migrate everyone within an acceptable downtime period. A multi-phase migration will necessitate coexistence. (We discuss coexistence issues from an architectural perspective in Chapter 16, “Coexisting with Previous Versions of Exchange.”) Coexistence is the term used to describe a scenario in which two different platforms (in this case, Exchange 5.5 and Exchange 2003) need to exist side by side and interoperate seamlessly.

Maintaining Connections During Coexistence

You must consider a plethora of issues when living in a dual-platform environment. We’ll discuss them now.

Connectors Between Platforms

To connect dissimilar platforms, you need some type of connection between the platforms during the migration period. If you’re moving from Exchange 5.5 to Exchange Server 2003, you can use the Active Directory Connector (ADC). If you’re coming from another system, you can use an SMTP Connector or an X.400 Connector. The essential point to understand here is that Exchange 2003 will work with most connectors, and you should plan the way that messages will be transferred internally between groups during the migration period.

Maintaining External Addresses

If your users receive e-mail from other systems in your organization or from outside your organization, your users’ external e-mail addresses should be preserved. With good planning, you can attach these addresses to the migrated mailboxes, which we’ll discuss in Chapter 15. If you elect to not do this, your users will need to inform others of their e-mail addresses.

Naming Conventions

You’ll need to take a look at naming conventions. Both your current conventions and the ones you’d like to use in Exchange 2003 should be discussed and formalized before starting the migration.

Directory Names The directory name is also known as the common name. This common name is used by Active Directory to create the unique full directory name of a mailbox. It is visible only in the Exchange System Manager (ESM). The default directory name is the same as the alias name but without spaces. Directory names cannot be changed after they are created, so be sure you like your convention before creating the mailbox.

Display Names The display name appears in the address book and can be changed at any time. Migrated messages use the display names of the senders and recipients. If you change the display names during the migration, replies to migrated e-mail can fail if an association between the old and new display names cannot be established.

By default, the first and last names are used to create the X.400 e-mail addresses. The alias is used to create the SMTP address. The alias is visible to the public and can contain spaces, unlike the directory name. Be sure that your naming convention states whether the nickname should be used for the first name or the display name. You’ll also need to consider how to handle duplicate names and hyphenated names.

Managing Migrated Messages

After a mailbox is migrated, the old mailbox can contain messages that were sent during the mailbox migration. In Exchange 5.5, you can configure the old mailbox to forward e-mail to the new mailbox. However, if you are running a system that doesn’t support e-mail forwarding or if you haven’t configured the Exchange 5.5 mailbox to forward e-mail, your users will need to connect to the old mailbox to retrieve any messages that still appear there. You can ask your users to perform this task before their Outlook profiles are reconfigured to point to the new mailbox.

You must consider a few issues so that users can avoid problems when replying to migrated messages. First, if only one display name matches the display name in the message, Exchange can resolve the address and forward the message without a problem. However, if more than one display name matches the display name in the message, the user is presented with a dialog box requesting her to select one name from a list of display names. This can be confusing for users when the display name in Exchange 5.5 matches the display name in Exchange 2003 and mailboxes exist in both platforms for the same user. You can easily see how such a scenario can cause trouble for you.

Second, if no display name in the address book matches the display name in the message, the user must find the new address in the address list. If you are changing your naming conventions in Exchange 2003, you must educate your users about how to find other members of the organization by their new display names in the address book. This education will be key to your successful migration.

For a user to be able to reply to a migrated message, the display name must appear in the address list either as a custom recipient or as a mailbox, but not as both.

Migrating Distribution Lists

During a multi-phase migration, in which addresses are constantly changing, migrating distribution lists can be a hassle. You can ensure correct routing to the members of a distribution list by planning to use one of the approaches in the following list. Each approach has benefits and limitations, and none is free of error, so you’ll need to test the approach you want to use before starting your migration.

• Migrate the distribution lists before migrating any mailboxes.

• Set up a forward scheme for each distribution list to a distribution group in Windows Server 2003.

• Maintain two lists on both systems. You must do this manually, and it is probably the least desirable option.

• Disable your distribution lists in Exchange 5.5 and create new distribution groups in Exchange 2003 after the migration is complete.