Information about a computer's MAPI installation can be found in the system registry on 32-bit client applications and in the Windows initialization file, WIN.INI, for 16-bit client applications. The system registry and WIN.INI file contain the same information about the MAPI libraries that are installed on the computer and options about use. All values in the registry entries are character strings.
Message service installation programs are responsible for creating the installation information in the [Mail] section of the WIN.INI file and in the following system registry key:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Messaging Subsystem
Message services can add entries to either the WIN.INI file, the system registry, or both resources depending on the installation.
The following table summarizes how clients retrieve version information and determine if Simple MAPI, CMC, MAPI, or the Active Messaging Library is available on their machine.
| To check | Registry/WIN.INI entry |
|---|---|
| Availability of Simple MAPI | Look for MAPI=1 |
| Availability of MAPI | Look for MAPIX=1 |
| Availability of CMC | Look for CMC=1 |
| Availability of Active Messaging Library | Look for OLEMessaging=1 |
| Available version of MAPI | Look for MAPIXVER string of the form:x.x.x |
Note Client applications that are running Windows NT 3.51 or earlier must check the WIN.INI file rather than the registry for the MAPIX=1 entry to determine the availability of Simple MAPI.