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XCLN: How Exchange Clients Use MSMAIL.INI and SHARED.INI

Article ID: 141272

Article Last Modified on 8/17/2005

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This article was previously published under Q141272

IMPORTANT: This article contains information about the registry. Before you edit the registry, you should first make a backup copy of the registry files (System.dat and User.dat). Both are hidden files in the Windows folder.

SUMMARY

This article describes how the Microsoft Exchange Windows client use the MSMAIL.INI and SHARED.INI files that are created by version 3.x of Microsoft Mail for Windows.

MORE INFORMATION

Microsoft Exchange 16-Bit Client

The Microsoft Exchange client for Windows 3.x does not support 32- bit extensions. It reads the MSMAIL.INI and SHARED.INI files, just like the Microsoft Mail client for Windows 3.x. On startup, the Exchange 16-bit client performs the following steps:
  1. The Exchange 16-bit client searches the [Options] section of EXCHNG.INI for the SharedExtsDir, SharedExtsServer, and SharedExtsPassword entries. If found, an anonymous connection to the server is made with the provided password. Then a search for the SHARED.INI file in the directory specified by any SharedExtsDir entry is performed.
  2. The Exchange 16-bit client searches the MSMAIL.INI file for a SharedExtensionsDir entry. If found, Exchange will search for the SHARED.INI file in the directory indicated. The Exchange 16- bit client will never look for the MSMAIL32.INI or SHARED32.INI file.
  3. If a SHARED.INI file is found, Exchange reads the extension entries specified in the [Custom Menus], [Custom Commands], and [Custom Messages] sections.
  4. The Exchange 16-bit client then reads the extension entries ([Custom Menus], [Custom Commands], and [Custom Messages] sections) specified in the MSMAIL.INI file.
The Exchange 16-bit client will ignore any extension entries whose version parameter is appended with a ',32' (for example, 3.0,32) as these are only supported by Exchange 32-bit clients.

NOTE: Specifying the bit of the extension in the version number will result in a syntax error if read by the Mail 3.x client for Windows 3.x or Microsoft Windows NT.

Microsoft Exchange 32-Bit Client

The 32-bit Microsoft Exchange client supports 16-bit Microsoft Mail 3.x client extensions as well as 32-bit extensions for the Microsoft Windows NT version of the Microsoft Mail 3.x client. The following steps describe how the extensions are read when the Microsoft Exchange 32-bit client starts up.
  1. The Microsoft Exchange 32-bit client will look for extensions in the HKEY_CURRENT_USER\Software\Microsoft\Mail\Microsoft Mail registry key. This is the location where extensions for the Microsoft Mail 3.x client for Windows NT are installed. In order to be consistent across 32-bit platforms, this registry is also used by the Microsoft Exchange client for Windows 95.
  2. The Microsoft Exchange 32-bit clients look in the registry for a SharedExtsDir in the KEY_CURRENT_USER\Software\Microsoft \Exchange\Client\Options registry key. If present, it also gets the SharedExtsServer and SharedExtsPassword entries. If the SharedExtsDir entry is not present, it looks in the MSMAIL32.INI file for the Microsoft Mail 3.x SharedExtensionsDir entry. If it is not found, it will use the MSMAIL.INI file to look for the SharedExtensionsDir. If a SharedExtensionsDir entry is found, it is parsed into the Microsoft Exchange equivalents. An anonymous connection to the server is made with the provided password, if required.
  3. The Microsoft Exchange 32-bit client looks in the shared directory for a SHARED32.INI file. If found, it will not look for SHARED.INI file.
  4. The Microsoft Exchange 32-bit client reads extensions ([Custom Menus], [Custom Commands], and [Custom Messages] sections) from the SHARED32.INI file found in step 3.
  5. The Microsoft Exchange 32-bit client reads extensions from the MSMAIL32.INI file.
  6. If the SHARED32.INI file is not found, the Microsoft Exchange 32-bit client looks for a SHARED.INI file in the same location.
  7. The Microsoft Exchange 32-bit client reads the MSMAIL.INI file.

Microsoft Exchange supports an enhancement to the version parameter of the extension registration entry. The version number can be followed by ',16' to indicate a 16-bit extension DLL or by ',32' to indicate a 32-bit extension DLL. If the version does not specify either of these settings, Microsoft Exchange assumes that the bit of the extension matches the bit corresponding to the file name.

For example, the MSMAIL32.INI file corresponds to 32 bits, and the SHARED.INI file corresponds to 16 bits. Specifying the bit of the extension in the version number will result in a syntax error if it is read by the Microsoft Mail 3.x client for either Windows 3.x or Windows NT.

For additional information on how the Microsoft Exchange client can be configured to exclude certain Microsoft Mail 3.x client extensions, please see the following article in the Microsoft Knowledge Base:

136804 Loading/Disabling MS Mail 3.x Win Client Extensions


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