SMTP / Routing Group connector state changes cause needless connector state toggling in Exchange 2000 Server

A Simple Mail Transport Protocol/Routing Group (SMTP/RG) connector may go into a "down" state temporarily, and then change within a minute to an "up" state after Advanced Queuing (AQ) retries the connector and determines that the SMTP/RG service on the target server is responding. This issue can occur if an SMTP/RG server on the other side does not close the connection properly. When a connector is in a down state, AQ flags the connector to indicate that it is in an error state. This type of connector state toggling can occur many times in an hour.

This issue impacts performance because it causes needless routing group version changes, which are associated with costly ResetRoutes AQ calculations. This issue also causes needless administrative notifications to be sent to the Exchange 2000 administrator if Exchange 2000 is configured to send notifications (to do so, click to expand Tools in Exchange System Manager, and then click to expand Monitoring and Status).

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To resolve this issue yorself, edit the registry to delay the forwarding of connector state changes and server changes (DMON info) by an amount of time that you specify in the registry. You can also edit the registry to eliminate redundant elements on that queue, so that the "connector down" element is deleted when the queue also contains "connector up" elements. If you configure these settings, Exchange 2000 only sends the most recent relevant connector state and server information notification when Exchange 2000 empties the queue.

The StateChangeDelay value affects the interval at which connectors are marked down and the notifications that occur as a result of connector and server state change. If you set this value, a server can only be marked up or down once in each time period that is set in the StateChangeDelay value.

Warning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall your operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.
To add the StateChangeDelay value:

1. Start Registry Editor (Regedt32.exe).
2. Locate and click the following key in the registry:
   HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\RESvc\Parameters
3. On the Edit menu, click Add Value, and then add the following registry value:
   Value name: StateChangeDelay
   Data type: REG_DWORD
   Radix: Decimal
   Value data: Set this value to the number of seconds that you want between updates (if you do not set this value, the default is 300, which is 5 minutes)
4. Quit Registry Editor.
5. You need to restart the Simple Mail Transport Protocol service (Smtpsvc) and the Routing Engine service (Resvc) for this change to take effect.

Set the second parameter only in a situation where it is truly non-critical if the connector goes down. To add the SuppressStateChanges value:

1. Start Registry Editor (Regedt32.exe).
2. Locate and click the following key in the registry:
   HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\RESvc\Parameters
3. On the Edit menu, click Add Value, and then add the following registry value:
   Value name: SuppressStateChanges
   Data type: REG_DWORD
   Radix: Decimal
   Value data: If you set this value to any value other than zero, you suppress all link state changes on this server (defaults to 0).
4. Quit Registry Editor.
5. You need to restart the Simple Mail Transport Protocol service (Smtpsvc) and the Routing Engine service (Resvc) for this change to take effect.

In the scenario that is described in the "Symptoms" section of this article, the most recent notification is most likely to be connector up, because the connector down state is retained for only one minute before AQ reverses the connector down state. When a connector up packet arrives at the master, the routing group version number is not incremented because (as is also most likely the case) the connector is already known to be up. Therefore, these registry changes avoid needless and costly ResetRoute AQ calculations.

The default value of the delay time-out (when this registry entry is not enabled) is 300 seconds, or 5 minutes. Modify this registry entry only in the situation that is described in the "Symptoms" section of this article. This is accomplished by setting the registry delay value as necessary (for example, to 600 seconds [10 minutes]), and restarting the Simple Mail Transport Protocol service (Smtpsvc) and the Routing Engine service (Resvc). There are two possible values that you can add to neither of them are set or created by default

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