Supported MAPI configurations (288836)

MORE INFORMATION

This article contains a general description of what type of MAPI configuration you should have with certain setups, and the level of programming support you can expect for each. This article assumes that you have not installed a third-party product that installs its own implementation of MAPI, because the third-party product usually replaces the Mapi32.dll file with its own version. Microsoft does not offer any support for third-party implementations of MAPI.

More information about Mapi32.dll

Depending on your system setup, Mapi32.dll can be a full implementation of MAPI, or it can be a stub dynamic-link library (DLL). Starting with Microsoft Outlook Express version 5.0 and Microsoft Outlook 2000, Mapi32.dll was changed to a stub DLL that redirects MAPI calls to the appropriate DLL, allowing multiple MAPI implementations to reside on one computer. The stub DLL reads entries in the registry to determine which MAPI implementation to use, based on what application is making a MAPI call. For example, if Outlook Express makes a MAPI call, Mapi32.dll checks the registry for the location of the MAPI implementation for Outlook Express, and then redirects the call to the appropriate DLL.

Note You can also run Fixmapi.exe to generate this stub. For more information, click the following article number to view the article in the Microsoft Knowledge Base: For more information about the MAPI stub DLL and the registry keys involved, see the "Mapi32 Stub Library" topic in the Microsoft Developer Network (MSDN). This topic explains how to explicitly map your application to a specific MAPI DLL and how to install or restore the MAPI stub DLL.

Note Outlook 2000 is specifically hard-coded to use its version of MAPI, regardless of the existence of the MAPI stub library.

Configurations

If you have:

• Microsoft Windows 95 or Microsoft Windows NT 4.0: These versions of Windows ship with Windows Messaging System (WMS), which provides Extended MAPI. However, this version of MAPI does not include providers to work against Exchange.
• Microsoft Windows 98 or Microsoft Windows 2000: If your system was upgraded from either Microsoft Windows 95 or Windows NT 4.0, it retains WMS from the previous installation. However, if your system was not upgraded from Windows 95 or Windows NT 4.0, WMS is not installed.
  
  For more information about how to obtain WMS, click the following article numbers to view the articles in the Microsoft Knowledge Base:

  235713 How to reinstall Microsoft Fax and Windows Messaging

  254458 Windows 2000 does not include Windows Messaging by default

• Windows with Outlook Express: In addition to WMS, Outlook Express provides Simple MAPI implementation. Simple MAPI is not as powerful as Extended MAPI, and does not support all MAPI interfaces and methods.
  
  For more information about Simple MAPI and Outlook Express, click the following article number to view the article in the Microsoft Knowledge Base:

  239576 Developer support limitations with Outlook Express

• Windows with Microsoft Outlook: This depends on the type of installation you have for Outlook. Outlook 98 and Outlook 2000 have the option of installing in Internet Mail Only or Corporate or Workgroup mode.
  
  For more information about how to determine what type of installation you have, click the following article number to view the article in the Microsoft Knowledge Base:
  To determine what type of installation you have, see the following articles in the Microsoft Knowledge Base:

  184029 How to tell what type of Outlook setup you have

  196041 How to know what type of Outlook Setup options that you are using

  • Internet Mail Only mode: The MAPI subsystem that is installed in this mode is a stub that provides minimal MAPI support for basic Outlook functions. MAPI development is not supported in this mode.
    
    For more information, click the following article number to view the article in the Microsoft Knowledge Base:

    252720 MAPI and CDO are not supported in Outlook IMO mode

  • Corporate or Workgroup mode: A full Extended MAPI subsystem is installed in this mode. Microsoft provides full development support for this configuration.
• Windows with Exchange Administrator (Exchange 5.5): Installing Exchange Administrator provides a fully supportable version of the MAPI subsystem (both Extended and Simple). The Mapisvc.inf file is not updated and does not contain entries for Exchange services, but users can edit this file.
  
  For more information, click the following article number to view the article in the Microsoft Knowledge Base:

  294470 How to add entries for Exchange services to Mapisvc.inf

• Windows with Exchange System Manager (Exchange 2000): Installing Exchange System Manager provides a fully supportable version of the MAPI subsystem (both Extended and Simple). However, although the Mapisvc.inf file is updated, the entries for the Exchange services are not added.
  
  For more information, click the following article number to view the article in the Microsoft Knowledge Base:

  294470 How to add entries for Exchange services to Mapisvc.inf

• Windows with Microsoft Exchange Server: This configuration has a fully supportable version of the MAPI subsystem.

Note The versions of MAPI which ship with Exchange are better suited for server-side applications than the versions that ship with Microsoft clients (Outlook, for example). Exchange's MAPI is designed to handle higher stress loads in unattended scenarios, which is not a priority for a MAPI client like Outlook.