How do I enable the tar pit feature?

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:

The tar pit feature can be enabled and configured by setting a registry key. To do this, follow these steps.

Note If the TarpitTime registry entry does not exist, Exchange behaves as if the value of this registry entry were set to 0. When the registry entry has a value of 0, there is no delay when the SMTP address verification responses are sent.

1.	Click Start, click Run, type regedit in the Open box, and then click OK.
2.	Locate and then click to select the following registry subkey: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SMTPSVC\Parameters
3.	On the Edit menu, point to New, and then click DWORD Value.
4.	Type TarpitTime as the registry entry name, and then press ENTER.
5.	On the Edit menu, click Modify.
6.	Click Decimal.
7.	In the Value data box, type the number of seconds that you want to delay SMTP address verification responses for each address that does not exist. Then, click OK. For example, type 5, and then click OK. This delays SMTP address verification responses for 5 seconds.
8.	Quit Registry Editor.
9.	Restart the Simple Mail Transport Protocol (SMTP) service