Microsoft KB Archive/281154

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Article ID: 281154

Article Last Modified on 10/28/2006


  • Microsoft Exchange 2000 Conferencing Server

This article was previously published under Q281154


The following error message may be generated on the T.120 Multipoint Control Unite (MCU) Conferencing server:

Source: MSExchangeT120
Type: Error
Category: Internal
Event ID: 12290
Description: The Microsoft Exchange Data Conferencing service service could not locate a Machine certificate in the store. You will be unable to create secure conference until the certificate is found.


If a Microsoft Certificate Authority (CA) service was installed after the Microsoft Exchange Conferencing service, the auto-enrollment object that is used to request a computer or "machine," certificate will not be issued.


An administrator must manually request a computer certificate, which will be used for secure conferencing. The following steps outline the proper procedure needed to resolve this issue.

Active Directory Users and Computers MMC Snap-In

  1. Click the domain object, and then right-click Properties.
  2. Click the Group Policy tab, and then click Edit.
  3. Expand the Computer Configuration object, and locate the following object:

    Windows Settings\Security Settings\Public Key Policies\Automatic Certificate Request

  4. Right-click the object, click New, and then click Automatic Certificate Request.
  5. Click the Computer object, and then click Next.
  6. Click the appropriate Certificate Authority (CA), click Next, and then click Finish.
  7. Verify that the certificate enrollment object actually showed up.

NOTE: The preceding steps assume that the T.120 MCU computer is a member of the Domain Computers group. If not, you must follow the procedures outlined in the following Microsoft Knowledge Base article, which explains how to add your conferencing server to the Domain Computers group, whether it is in the same domain as the Certificate Authority or in a child domain:

252789 XCCC: Configuring Secure Conferencing Capabilities for Computers Located in a Child Domain

Keywords: kberrmsg kbprb KB281154