IMSProvider : IUnknown

Last modified: July 23, 2011

Applies to: Outlook

Provides access to a message store provider through a message store provider object. This message store provider object is returned at provider logon by the message store provider's MSProviderInit entry point function. The message store provider object is primarily used by client applications and the MAPI spooler to open message stores.

Header file:


Exposed by:

Message store provider objects

Implemented by:

Message store providers

Called by:

MAPI and the MAPI spooler

Interface identifier:


Pointer type:



Closes a message store provider in an orderly fashion.


Logs MAPI on to one instance of a message store provider.


Logs the MAPI spooler on to a message store.


Compares two message store entry identifiers to determine whether they refer to the same store object.

MAPI uses one message store provider object per session, no matter how many message stores are opened by the store provider. If a second MAPI session logs on to any open stores, MAPI calls MSProviderInit a second time to create a new message store provider object for that session to use.

A message store provider object must contain the following to operate correctly:

  • An lpMalloc memory-allocation routine pointer for use by all stores opened by using this provider object.

  • The lpfAllocateBuffer, lpfAllocateMore , and lpfFreeBuffer routine pointers to the MAPIAllocateBuffer, MAPIAllocateMore, and MAPIFreeBuffer memory allocation functions.

  • A linked list of all the stores opened by using this provider object and not yet closed.