Registering Service Provider Unique Identifiers

Address book, message store, and transport providers use a unique identifier known as a MAPIUID to register to service objects of various types. A MAPIUID is a 16-byte identifier that contains a globally unique identifier, or GUID. You can create a MAPIUID by:

Defining a constant.
Invoking the Microsoft utility UUIDGEN.EXE.

For example, an address book provider might include the following constant in a header file to define a MAPIUID:

#define AB_UID_PROVIDER  { 0Xe3, 0x3c, 0x67, 0xa0, \
                           0xc8, 0x1f, 0x11, 0xce, \
                           0xb2, 0xe4, 0x0, 0xaa, \
                            0x0, 0x51, 0xe, 0x3b  }

To register a MAPIUID if your provider is an address book or message store provider

Call IMAPISupport::SetProviderUID.

Register a MAPIUID for each logon object that you instantiate and include this MAPIUID in the first 16 bytes of the ab member of every entry identifier that you create. MAPI uses MAPIUIDs to associate objects with service providers. When a client calls the IMAPISession::OpenEntry method to open an object, MAPI examines the MAPIUID portion of the entry identifier, matching it against the registered MAPIUID, to determine which logon object should receive the open request.

If your provider is a transport, register one or more MAPIUIDs when MAPI calls your IXPLogon::AddressTypes method. MAPI uses the MAPIUIDs registered by transport providers to assign responsibility for message delivery.

Although service providers typically register a single MAPIUID, you can register multiple MAPIUIDs. If your address book or message store provider supports multiple logon objects, perhaps by permitting a user to add more than one instance of your provider to their profile, you might want to implement a different MAPIUID for each logon object. There are a few other reasons to support more than one MAPIUID:

You must support more than one version of your provider and the entry identifiers must represent the appropriate version. Assign a different MAPIUID for each version.
You want to distinguish between the types of objects you support. For example, an address book provider might want to register one MAPIUID to use in the entry identifiers of its messaging user objects and a different MAPIUID to use for distribution lists.

When there are multiple logon objects that are concurrently active, it makes sense to have unique MAPIUIDs for each one. This increases the accuracy with which MAPI matches entry identifiers to service providers and saves some work. When every logon object has its own unique identifier, MAPI can guarantee that any request it routes to a logon object can be handled by that object. When logon objects share MAPIUIDs, MAPI routes the request to the first logon object that is identified by the MAPIUID. If one of your logon objects receives a request that it cannot process because it does not handle the entry identifier, pass the request on to your next logon object before returning an error.