Installing the MAPI Subsystem

Last modified: November 08, 2011

Applies to: Outlook

Supported versions of Windows install the MAPI stub library, Mapi32.dll, in the <drive>\Windows\System32 folder.

The supported versions of Windows are as follows:

  • Windows 7.

  • Windows Vista.

  • Windows Server 2008.

  • Windows Server 2003.

  • Windows XP.

To correctly install the MAPI subsystem, install an application that contains a MAPI-based subsystem, such as Microsoft Outlook.

You can find information about a computer's MAPI subsystem installation in the system registry. All values in the registry entries are character strings.

Message service installation programs are responsible for creating the installation information in the following system registry key:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Messaging Subsystem

Message services must add entries to the system registry.

The following table summarizes how clients retrieve version information for the MAPI subsystem on their computer.

To check


Availability of MAPI

Look for MAPIX=1.

Available version of MAPI

Look for a MAPIXVER string of the form "x.x.x".