MTA Stacks service supportability guidelines for Exchange 2000 Server and Exchange Server 2003

The Message Transfer Agent (MTA) Stacks service in Microsoft Exchange 2000 Server and in Microsoft Exchange Server 2003 is frequently used to provide backward-compatible message transfer services between Exchange 2000 Server or Exchange Server 2003 servers and Microsoft Exchange Server 5.5 servers in a mixed-mode environment.

When the transition is made to a pure Exchange 2000 Server or Exchange Server 2003 native-mode environment, administrators may want to disable the MTA Stacks service.

We do not recommend that you disable the MTA Stacks service in Exchange 2000 Server. This action is not supported. The MTA Stacks service is a core operational component. You may experience unexpected behavior if you disable this service. In Exchange 2000 Server, the MTA Stacks service is required to correctly process mailbox moves and for other core functions. These dependencies on the MTA Stacks service have been removed in Exchange Server 2003. Therefore, Microsoft supports Exchange Server 2003 deployments in which the MTA Stacks service is disabled.

How to disable the MTA Stacks service on Exchange Server 2003

Note The MTA Stacks service must remain enabled on an Exchange Server 2003 server if the following conditions are true:

• The server is a transport bridgehead to Exchange Server 5.5 servers.
• The server is running the GroupWise connector.
• The server is running the Notes connector.
• The server is running another Exchange Development Kit (EDK) connector, such as a third-party Fax connector

The MTA Stacks service is also required for direct connectivity with external X.400 mail systems.

How to disable the MTA Stacks service on an Exchange Server 2003 stand-alone server

To disable the MTA Stacks service on Exchange Server 2003 stand-alone servers, follow these steps.

Note Before you disable the MTA Stacks service on the stand-alone server, use Exchange System Manager to verify that there are no queued messages in the MTA Stacks service.

Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:

1. Click Start, point to Administrative Tools, and then click Services.
2. Right-click Microsoft Exchange MTA Stacks, and then click Properties.
3. In the Startup type list, click Disabled.
4. Click Stop, and then click OK.
5. Close the Services window.
6. Start Registry Editor.
7. Locate and then click the following registry subkey, where ServerName is the name of the Exchange Server 2003 server:
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIS\ServerName
   For each private or public database that is listed under this subkey, perform steps 8 to 11.
8. Right-click the Gateway In Threads value, and then click Modify.
   
   If the Gateway In Threads value does not exist, you must create it. To do this, right-click the database key, point to New, and then click DWORD Value. Name this new value Gateway In Threads.
9. Type 0 in the Value data box, and then click OK.
10. Right-click the Gateway Out Threads value, and then click Modify.
    
    If the Gateway Out Threads value does not exist, you must create it. To do this, right-click the database key, point to New, and then click DWORD Value. Name the new value Gateway Out Threads.
11. Type 0 in the Value data box, and then click OK.
12. Quit Registry Editor.

Note The changes that you made in steps 8 through 11 will not take effect until the Microsoft Exchange Information Store service is restarted.

When you set the Gateway In Threads value and the Gateway Out Threads value to 0, Store and MTA connection failure events are not logged in the Application log after the MTA Stacks service has been disabled. If you create a new database on the server, you should set the Gateway In Threads value and the Gateway Out Threads value for the new database.

You should add the procedure that is described in this section to your Exchange server build out documentation and to your Mailbox Store creation documentation.

How to disable the MTA Stacks service on Exchange Server 2003 cluster servers

Important In an Exchange cluster, the MTA Stacks service is hosted by the first Exchange virtual server that is created in the cluster. All other Exchange virtual servers share this one MTA resource. After the MTA resource is deleted from an Exchange cluster, you cannot re-add the MTA resource by just adding it back to the cluster. You can only re-add the MTA resource by performing a failure recovery sequence with the Exchange virtual server that has previously hosted the MTA resource. You must delete the Exchange System Attendant resource and then re-add the same Exchange System Attendant resource. When you do this, an MTA resource that has the same configuration settings as the previous MTA resource is created. Also, if you remove of the MTA resource, the Exchange virtual server deletion or removal logic will not be changed. You cannot remove the Exchange virtual server that previously hosted the MTA Stacks service unless the Exchange virtual server is the only Exchange virtual server that remains in the cluster. For example, If there is more than one Exchange virtual server in the cluster, the Exchange virtual server that previously hosted the MTA resource can only be removed after all other Exchange virtual servers are removed.

To disable the MTA Stacks service on Exchange Server 2003 clustered servers, follow these steps on each Exchange cluster.

Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:

1. Delete Exchange Message Transfer Agent Instance cluster resource:
   1. Start Cluster Administrator, and then connect to the cluster that you want to administer.
   2. Expand the cluster group that contains the Exchange MTA resource .
   3. Right-click the MTA resource, and then click Delete.
   4. Click Yes.
2. Click Start, point to Administrative Tools, and then click Services.
3. Right-click Microsoft Exchange MTA Stacks, and then click Properties.
4. In the Startup type list, click Disabled.
5. Click Stop, and then click OK.
6. Close the Services window.
7. Start Registry Editor.
8. Locate and then click the following registry subkey, where ServerName is the name of the Exchange Server 2003 server:
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIS\ServerName
   For each private or public database that is listed under this subkey, perform steps 9 to 11.
9. Right-click the Gateway In Threads value, and then click Modify.
   
   If the Gateway In Threads value does not exist, you must create it. To do this, right-click the database key, point to New, and then click DWORD Value. Name this new value Gateway In Threads.
10. Type 0 in the Value data box, and then click OK.
11. Right-click the Gateway Out Threads value, and then click Modify.
    
    If the Gateway Out Threads value does not exist, you must create it. To do this, right-click the database key, point to New, and then click DWORD Value. Name the new value Gateway Out Threads.
12. Type 0 in the Value data box, and then click OK.
13. Quit Registry Editor.

When you set the Gateway In Threads value and the Gateway Out Threads value to 0, Store and MTA connection failure events are not logged in the Application log after the MTA Stacks service has been disabled. If you create a new database or new Exchange virtual servers in the cluster, you should set the Gateway In Threads value and the Gateway Out Threads value for the new database or the new Exchange virtual server. Remember that you must fail over the new database or the new Exchange virtual servers to each node before the database registry keys will be generated.

You should add this procedure to your Exchange server build out documentation and to your Mailbox Store creation documentation.

Note Before you disable the MTA Stacks service on the cluster server, use Exchange System Manager to verify that there are no queued messages in the MTA Stacks service. Also, make sure that the Exchange virtual servers within the cluster have been brought online at least one time on every potential node in the cluster. This includes active and passive nodes. This action is required to create the MDB-specific registry keys. For example, the Private-GUID_of_private_mdb registry key is created after the Exchange virtual servers are brought online.

For more information about the MTA Stacks service in Exchange 2000 Server, click the following article number to view the article in the Microsoft Knowledge Base: For more information about X.400 message flow in Exchange 2000 Server, click the following article number to view the article in the Microsoft Knowledge Base: