Applies to: Exchange Server 2007 SP3, Exchange Server 2007 SP2, Exchange Server 2007 SP1, Exchange Server 2007
Topic Last Modified: 2007-08-07

This topic explains how to disable Messaging Application Programming Interface (MAPI) access for all mailboxes on a Mailbox server. To perform this procedure, you must edit the registry.

Incorrectly editing the registry can cause serious problems that may require you to reinstall your operating system. Problems resulting from editing the registry incorrectly may not be able to be resolved. Before editing the registry, back up any valuable data.

After you disable MAPI on a server, Office Outlook 2003 and Office Outlook 2007 client computers receive the following error message:

Your Microsoft Exchange administrator has blocked the version of Outlook that you are using. Contact your administrator for assistance.

If an Outlook client computer is connected to the server when the registry change is applied, the client computer will immediately be disconnected and will return the following message:

Connection to Microsoft Exchange has been lost. Outlook will restore the connection when possible.

Before You Begin

To perform this procedure, the account you use must be delegated membership in the local Administrators group.

For more information about permissions, delegating roles, and the rights that are required to administer Microsoft Exchange Server 2007, see Permission Considerations.


To use Registry Editor to disable MAPI for all mailboxes on a server

  1. Start Registry Editor.

  2. Locate, and then click to select the following registry subkey:


  3. On the Edit menu, point to New, and then select String value.

  4. Rename the value to Disable MAPI Clients.

  5. Double-click the Disable MAPI Clients value, and in the Edit String box under Value Data, type the version or range of versions to disable:

    • To disable a specific MAPI client version, type: 12.1234.01

    • To disable a range of MAPI client versions, type: 11.1234.01-12.1234.01

    • To disable an open-ended range of MAPI client versions, type: -12.1234.01 or 11.1234.01-

    • To disable multiple sets of MAPI client versions, use either commas or semicolons to separate the sets as follows: 11.1234.01-11.9999.01;12.1234.01-12.5000.01

    To determine the MAPI client version for Microsoft Outlook clients, view the file version of the Emsmdb32.dll file.
    The version of the Emsmdb32.dll file is listed as X.0.Y.Z. This version must be entered as X.Y.Z in the registry value. For example, if the version of Emsmdb32.dll is 12.0.4407.1004, enter 12.4407.1004 in the Disable MAPI Clients registry value.
    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 an Exchange server.
  6. Exit the Registry Editor.

This registry value applies to all mailboxes on the server. If you move a mailbox to this server, this setting will apply to the moved mailbox.
  1. (Optional) To apply the registry key, restart the Microsoft Exchange Information Store service. If you do not restart the Microsoft Exchange Information Store service, the service will query the registry key every 15 minutes and apply any changes. Any open connections with a newly blocked version will be disconnected immediately after the registry key is applied. Any new connections will be blocked.

For More Information

For information about how to enable or disable MAPI for an individual mailbox, see How to Enable or Disable MAPI for a Mailbox User.