Exchange Server Migration

Move Mailbox Method
One way to upgrade to Exchange 2000 Server is to move mailboxes from an existing Exchange Server 4.0 or Exchange Server 5.x server to an Exchange 2000 server. With this method, you install Exchange 2000 Server in the existing Exchange Server site, and then move all mailboxes and public folders to it.

To move mailboxes from an Exchange Server 4.0 or Exchange Server 5.x server, you must have at least one Exchange Server 5.5 server in that site. You can install Exchange 2000 only in a site that has an Exchange Server 5.5 SP3 or later server. If you do not have an Exchange Server 5.5 server in that Exchange Server 4.0/5.0 site, you cannot install Exchange 2000 in it.

Some advantages of the move mailbox method include:
Minimal downtime. The only downtime is the time that you have to have to move the user's mailbox data. Because of this, the move mailbox method is the preferred method of upgrading to Exchange 2000 Server.
You can directly upgrade users on Exchange Server 4.0 and Exchange Server 5.0 computers to Exchange 2000 Server.
Not all users have to be upgraded to Exchange 2000 at the same time.
Client profiles are automatically reconfigured after the mailbox is moved and the user logs on.

Some disadvantages of the move mailbox method include:
Older version connectors cannot be moved.
ExMerge cannot move Public Folder data.

Swing Upgrade Method
The swing method gives you the flexibility of the move mailbox method of upgrading, but with the swing method, you do not have to purchase new hardware for each existing server. With the swing method, an organization can purchase one or two new servers while upgrading the whole organization to Exchange 2000 Server, and then the organization can use the move mailbox method to move data onto the new servers. The old Exchange Server 5.5 computers are upgraded to or reinstalled with Exchange 2000 Server, verified as stable, and then redeployed into production. At that point, the mailboxes are moved back to the original server hardware.

With the swing method you can upgrade to newer, more powerful hardware, and then reintroduce it into the production environment with minimal disturbance to your users.

Some advantages of the swing method include:
Minimal downtime. The only downtime is the time that it takes to move the user's mailbox data.
You can upgrade users on Exchange Server 4.0 and Exchange Server 5.x computers.
No operating system, Exchange Server, or hardware upgrades occur on the existing server until users are fully moved to another server.
Client profiles are automatically reconfigured after the mailbox is moved and the user logs on

Some disadvantages to the swing method include:
You cannot move older version connectors.
You cannot move Key Management Server (KMS).

In-Place Upgrade Method
With the in-placed upgrade method, you can take an existing Exchange Server 5.5 SP3 or SP4 server and install Exchange 2000 Server on it. In this way, you upgrade your existing Exchange Server databases and connectors to Exchange 2000 Server. When you use this method, you must perform all prerequisites and testing for the installation of Exchange 2000 Server. If you do not do so, the result may be significant downtime for you users and possible loss of e-mail data if you did not make correct backups.

Some advantages of the in-place upgrade method are that it:
Offers the shortest migration time, because all data is upgraded at the same time.
Does not require any additional server hardware.
This method of upgrade can cause problems if you do not do all prerequisites for the upgrade and installation of Exchange 2000 Server. This can result in significant downtime for users.

If you must use this method of upgrade because of hardware availability limitations, Microsoft strongly recommends that you get backups before the upgrade in the form of online backups, offline backups, and backups in the form of personal folder (.pst) files through the use of ExMerge. With a backup in .pst format, you can run a clean installation of Exchange 2000 Server, and then import your data directly from your .pst files if an in-place upgrade fails, instead of rebuilding your Exchange Server 5.5 server and restoring from backup. This method has the same disadvantages as the ExMerge Method. At a minimum, an unsuccessful in-place upgrade recovery includes the following steps:
Manually remove Exchange 2000 Server from the server.
Manually remove Exchange Server objects from Active Directory.
Reinstall Exchange Server 5.5
Restore Exchange Server 5.5 data from backups.
Troubleshoot to determine reasons for the unsuccessful upgrade.