Collaboration Data Objects (CDO) 1.2.1 is not supported with Outlook 2010 and later versions


Although the Collaboration Data Objects (CDO) 1.2.1 object library could be used with Microsoft Outlook 2010 and later verisons, we do not recommend or support this in any way.

Important: This article applies to using CDO 1.2.1 client-side together with Outlook 2010 and later versions. It does not apply to using CDO 1.2.1 that installs the MAPI subsystem and that is designed for use on a computer without Outlook.

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Collaboration Data Objects (CDO) 1.2.1 is a client library that provides a thin wrapper over Extended MAPI functionality. This library is typically used to add email messaging functionality to custom programs. This library allows those programs to perform functions such as sending email through MAPI, working with calendars, and accessing various data in Microsoft Outlook or in Microsoft Exchange.

Starting with Outlook 2007, CDO 1.2.1 has not been included with Microsoft Outlook. But CDO 1.2.1 is available only as a download for Outlook 2007:

This download can only be installed on a computer that has Outlook 2007 installed. If Outlook is not installed, you receive the following error message when you run the ExchangeCdo.msi file:

Collaboration Data Objects 1.2.1 cannot be installed unless Microsoft Office Outlook 2007 is also installed.

Although the downloadable version of CDO is not installed when Outlook 2010 or a later version is installed, you could install CDO first with Outlook 2007 before you upgrade Outlook. In this scenario, programs can still use the CDO library to integrate with the Outlook 2010 or later version of MAPI.

However, we recommend that CDO is first uninstalled before Outlook is upgraded from Outlook 2007 to Outlook 2010 and later versions.

To uninstall CDO, follow these steps:

  1. Download and run ExchangeCDO.exe from the following Microsoft Download Center link:
  2. Extract the downloaded executable to a folder on your local disk.
  3. Run the extracted ExchangeCDO.exe file.
  4. Select Remove and then click Next.
  5. When setup is complete, click Finish.

Microsoft Outlook 2010 and later versions include many architectural changes to the client-side MAPI subsystem. Of particular concern are scenarios in which Outlook is configured to use multiple Exchange accounts. Also, CDO 1.2.1 is a 32-bit client library and will not operate with 64-bit versions of Outlook. Given all these factors, CDO 1.2.1 is not supported for use with Outlook 2010 or later versions, and we do not recommend its use with Outlook 2010 and later versions.

Programs that use CDO should be re-designed to use other Application Programming Interfaces (APIs) instead of CDO. Starting with Outlook 2007, the Outlook object model was greatly expanded to provide functionality that was previously available only by using CDO 1.2.1. The Outlook 2010 and later versions object model includes some new features to expand on this more. For example, the Outlook object model has new functionality to operate correctly with multiple Exchange accounts. The Outlook object model also works for both 32-bit and 64-bit versions of Outlook. Developers should use the Outlook 2010 and later object model instead of CDO 1.2.1. Also, developers can still use Extended MAPI (which requires unmanaged C++) in some scenarios where CDO was required. However, if it is possible, we generally recommend that the Outlook object model be used instead of Extended MAPI.

Microsoft product support can help developer customers migrate custom programs from using CDO 1.2.1 to using other APIs. However, Microsoft will not provide support for any scenarios in which CDO 1.2.1 is used with Outlook 2010 or Outlook 2013.