XCLN: MAPIFindNext Fails to Retrieve Message Identifiers

• Microsoft Exchange Windows 95 client, version 4.0
• Microsoft Exchange Windows 3.x client, version 4.0
• Microsoft Exchange Windows NT client, version 4.0

SYMPTOMS

Using the simple MAPI function MAPIFindNext in MAPI version 1.0 may fail to retrieve the next (or first) message identifier of a specified type of incoming message. The following is the resulting return code of the MAPIFindNext call:

   MAPI_E_NO_MESSAGES

CAUSE

When you use MAPI version 1.0, choosing the value "IPM." for parameter lpszMessageType in the MAPIFindNext function call does not retrieve the next message identifier of the specified type (IPM) of incoming message. This value has been used successfully in previous versions of simple MAPI to enumerate all messages of a given message type.

WORKAROUND

Instead of using "IPM." as value to enumerate messages of an IPM message type, specify "NULL" (without the quotation marks) in the lpszMessageType parameter of the MAPIFindNext function call.

STATUS

Microsoft has confirmed this to be a problem in Microsoft Exchange version 4.0. This problem was corrected in the latest Microsoft Exchange 4.0 U.S. Service Pack. For information on obtaining the service pack, query on the following word in the Microsoft Knowledge Base (without the spaces):

   S E R V P A C K

MORE INFORMATION

The MAPI SDK online documentation states the following regarding the lpszMessageType parameter of the MAPIFindNext function:

   When the lpszSeedMessageID parameter is NULL or points to an empty
   string, MAPIFindNext returns the message identifier for the first
   message of the type specified by the lpszMessageType parameter. When
   lpszSeedMessageID contains a valid identifier, the function returns the
   next matching message of the type specified by lpszMessageType. Repeated
   calls to MAPIFindNext ultimately result in a return of the
   MAPI_E_NO_MESSAGES value, which means the enumeration is complete.
   Message type matching is done against message class strings. All message
   types whose names match (up to the length specified in lpszMessageType)
   are returned.

• ulResult = (*lpfnMAPIFindNext)(hMAPISession, hWnd, "IPM.", lpszSeedMessageID, flFlag, 0L, lpszMessageID);
• ulResult = (*lpfnMAPIFindNext)(hMAPISession, hWnd, NULL, lpszSeedMessageID, flFlag, 0L, lpszMessageID);

Installation

This description uses the Microsoft Exchange Windows NT client, version 4.0 as an example.

1. Close all applications that use Mapi32.dll

2. Back up Mapi32.dll from the <Winntroot>\System32 directory.

3. Copy the extracted version of Mapi32.dll to the <Winntroot>\System32 directory.

4. Restart any applications that were stopped in step 1.