An Exchange MAPI application does not work correctly when MAPI Stub is bypassed

When an application that can work with either Outlook or with Exchange's MAPI tries to load an Exchange MAPI (exmapi32.dll) component directly instead of loading a MAPI stub library on the computer, the application does not work correctly.

For example, you run the MfcMapi.exe tool, click Session/Load MAPI, enter the path of the exmapi32.dll file, and then click Session\Logon and Display Store Table. When you do this, you receive the following error message:
An internal MAPI error has caused this logon attempt to fail. MAPI 1.0 [000004CA]
Currently, Mapi32 Stub Library supports multiple MAPI components on a computer. However, in this case, some internal calls to mapi32.dll are bypassed to the exmapi32.dll Exchange MAPI component. When the MAPI stub is bypassed, the problem may occur because of the requests for unexpected MAPI operations.

Update information for the MAPI application

The following file is available for download from the Microsoft Download Center:

DownloadDownload the ExchangeMapiCdo.EXE package now.

For more information about how to download Microsoft support files, click the following article number to view the article in the Microsoft Knowledge Base:
119591 How to obtain Microsoft support files from online services
Microsoft scanned this file for viruses. Microsoft used the most current virus-detection software that was available on the date that the file was posted. The file is stored on security-enhanced servers that help prevent any unauthorized changes to the file.


You have to install this hotfix on any client that uses MAPI-based or CDO-based applications. The server to which you connect the client must be running Exchange Server 2003 Service Pack 2 or a later version.

Restart requirement

You do not have to restart the computer after you apply this update.

Update replacement information

This update does not replace a previously released update.

File information

The English version of this update has the file attributes (or later file attributes) that are listed in the following table. The dates and times for these files are listed in Coordinated Universal Time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time item in Control Panel.
File nameFile versionFile sizeDateTime
For more information, click the following article number to view the article in the Microsoft Knowledge Base:
836993 How to obtain the latest service packs for Exchange Server 2003
For more information about the Mapi32 Stub Library, visit the following Web site: For more information about the Microsoft Exchange server MAPI editor tool, visit the following Web site:
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

Article ID: 957537 - Last Review: 04/08/2009 14:57:13 - Revision: 1.0

Microsoft Exchange Server 2003 Standard Edition, Microsoft Exchange Server 2003 Enterprise Edition

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