How to Remove the Last Exchange 5.5 Server

The Administrator program removes the Exchange 5.5 server from the SRS database. The Config_CA object processes this deletion, then replicates it to AD.

As long as you have Exchange 5.5 servers in your Exchange organization, you need to run an SRS in your administrative group. The SRS acts as a shadow Exchange 5.5 directory while Exchange is running in mixed mode.

Remove the last Exchange 5.5 server in the organization by performing the following tasks. Note that you should take these actions only when you're deleting the last Exchange 5.5 server in an Exchange organization. The Microsoft article "XADM: Preparing a Mixed Mode Organization for Conversion to Native Mode" (http://support.microsoft.com/default.aspx?scid=kb;en-us; q272314) gives more detail about this process.

1. Back up the SRS and the Exchange databases.
2. Log on to the computer on which ESM is installed with an account that has Full Exchange Administrator and service account permissions on the SRS database.
3. Use the Active Directory Connector Management snap-in to delete any recipient CAs.
4. Don't delete any ConfigCAs. (ConfigCAs appear in the Active Directory Connector Management snap-in, with Config_CA as part of their name.)
5. Use Exchange Administrator to connect to the Exchange 2000 server that's running the SRS. Delete any DRCs on the SRS server.
6. Delete the last Exchange 5.5 server.
7. For all sites, delete the DRCs by using Exchange Administrator to connect to the SRS in each site.
8. Allow time for the changes made to the Exchange 5.5 directory to replicate to the AD ConfigCAs. Replication time depends on how efficiently directory replication takes place in your organization.
9. Open ESM and double-check that no Exchange 5.5 servers remain in the organization.
10. Under the Tools container, click the Site Replication Services container.
Right-click each SRS and delete it.
11. Use the Active Directory Connector Management snap-in to verify that the ConfigCAs for each SRS have been deleted. The deletion of each SRS automatically triggers the deletion of the ConfigCAs.
12. Allow time for the changes to replicate.
13. Delete all instances of the ADC.

When this procedure is complete, you can switch from mixed to native mode. To change the mode, open ESM. On the General tab of the Exchange organization's Properties dialog box, click Change Mode. Note that this process is a one-way operation; after you convert an organization to native mode, you can't set it back to mixed mode.

The Change Mode button will be disabled as long as Exchange 5.5 servers remain in the organization. If the Change Mode option is still disabled after you've removed all Exchange 5.5 servers, use ESM to check that no instances of the SRS remain. (Look under Tools, Site Replication Services.) Exchange doesn't automatically remove all SRS instances when you remove or upgrade Exchange 5.5 servers.

Disable the Service Account
After you retire the Exchange 5.5 servers, don't forget to delete the Exchange service account. This account has logon as service rights and Domain Administrator privileges. Domain Administrator rights are the most powerful privileges in a Windows NT 4.0 domain. A domain administrator can manage accounts, change passwords, take ownership of all files, and perform other tasks, so you should carefully control membership in the Domain Administrator global group. Make sure other applications aren't using the account. As a precaution, disable the account first for a few days before deleting it.

Update Your Documentation
Don't forget to update your documentation to reflect the changes you've made to your Exchange infrastructure. You might have transferred messaging connectors from your Exchange 5.5 servers to your Exchange 2000 servers. If you have a multi-tiered support organization, communicate the changes to the relevant people. Update your disaster-recovery procedures and server-build procedures, if necessary, and change any references to the server you removed.

Redeploy the Hardware
Think about how you can redeploy the server you've uninstalled from Exchange. My server was about 5 years old, and the hardware specification wasn't on the Windows 2000 Hardware Compatibility List (HCL). My company has redeployed legacy Exchange servers as Instant Messaging (IM) servers. IM imposes a light server load, so older servers can handle it. Or you might decide to reuse the hardware for testing.

Plan Carefully
Phasing out Exchange 5.5 servers from your organization requires careful planning and implementation. I've described the basic steps. The Microsoft articles in "Related Reading" will help you with the details. When the migration is complete, you can take advantage of all the benefits of managing Exchange 2000 in native mode.