This article describes a feature that you can use to disable MAPI client access to a computer that is running Microsoft Exchange Server 2007, Microsoft Exchange Server 2003, or Microsoft Exchange 2000 Server based on the version number of the Emsmdb32 file. This feature was introduced in Microsoft Exchange 2000 Server Service Pack 1 (SP1).

This feature lets you restrict access based on any one or more of the following items:

•	A single MAPI client version
•	A specific range of MAPI client versions
•	An open-ended range of MAPI client versions

This functionality can help prevent problematic or beta client MAPI providers from running against an Exchange computer.

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To disable MAPI client access, you must create the Disable MAPI Clients registry value. To do this, follow these steps.

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.	Start Registry Editor.
2.	Locate and then click the following registry subkey: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\MSExchangeIS\ParametersSystem
3.	On the Edit menu, click Add Value, and then add the following registry value: Value name: Disable MAPI Clients Value type: REG_SZ Value data: v1, v2-v3, -v4, v5-
4.	Exit Registry Editor.
5.	Restart the Microsoft Exchange Information Store service in the Services snap-in. Restart the Microsoft Exchange Information Store service in the Services snap-in even if you are in a cluster environment. Note This step is applicable only for Exchange 2000 Server. In Exchange Server 2003, changes to this registry key are dynamically detected. The following occurs in Exchange 2003: • Every 15 minutes, the store queries the registry key. • If the registry key changes, these changes are immediately put into effect. • If any current open connections are established with a newly blocked version, these connections are immediately disconnected. • All new connections are blocked if you are using a blocked version.

Note This registry value is read only during the startup of the Microsoft Exchange Information Store service.

You can indicate all the specific versions or ranges of versions that you want to disable in this string. Use Exchange System Manager to determine the version of MAPI clients that connect to the mailbox store. In Exchange System Manager, locate the Logons container of the mailbox store. The Client Version column displays the version of the MAPI clients that are connected to the mailbox store.

Important The MAPI client version is listed in Exchange System Manager as X.0.Y.Z. This version must be entered as X.Y.Z in the registry value. For example, if Exchange System Manager lists the MAPI client version as 5.0.2819.0, enter 5.2819.0 in the Disable MAPI Clients registry value.

Important Server-side Exchange components also use MAPI to log on. Some components report their client version as an Exchange build number. Therefore, avoid restricting 6.x.x on Exchange 2000 computers or on Exchange 2003 computers.

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To disable a single MAPI client version

Enter the appropriate value in the Value Data string. For example, to disable the MAPI client version 5.0.2653.22, use the following string as the Value Data string for the Disable MAPI Clients registry value:

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To disable a range of MAPI client versions

Use the v2-v3 format, where v2 is the earlier version number that starts the range of MAPI client versions that you want to disable.

For example, if you want to disable the access of all the MAPI client versions from 5.0.2653.11 to 5.0.2653.22, use the following string value for the Disable MAPI Clients registry value:

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To disable an open-ended range of MAPI client versions

Use the -v4 format or the v5- format. To disable the MAPI client version v4 and all earlier versions, use the format -v4. To disable the MAPI client version v5 and all later versions, use the v5- format.

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To disable multiple sets of MAPI client versions

Use any combination of the previous formats. Use commas (,) or semicolons (;) to separate the formats.

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Error message that is displayed on blocked MAPI clients

After you configure the Disable MAPI Clients registry value, disabled MAPI clients receive the following error message when they try to connect to the mailbox store:A Microsoft Office Outlook 2003 client receives the following error message:

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To determine the MAPI client version for Outlook clients

The MAPI client version for Outlook clients is the version of Emsmdb32.dll that is used for the Exchange store or for the transport MAPI provider. The MAPI client version for Outlook clients is not the version of any of the following files:

•	Msmapi32.dll
•	Mapi32.dll
•	Outlook.exe
•	Outllib.dll

For example, you have an Outlook client that has the following set of files:

File name	Version
Outlook.exe	11.0.6568.0
Outllib.dll	11.0.8001.0
Msmapi32.dll	11.0.6561.0
Emsmdb32.dll	11.0.8006.0

In this example, the version of Emsmdb32.dll that you can exclude or include is 11.0.8006.0.

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