The MAPIAllocateMore function allocates a memory buffer that is linked to another buffer previously allocated with the MAPIAllocateBuffer function.
SCODE MAPIAllocateMore( ULONG cbSize, LPVOID lpObject, LPVOID FAR * lppBuffer );
During MAPIAllocateMore call processing, the calling implementation acquires a block of memory from the operating system. The memory buffer is allocated on an even-numbered byte address. On platforms where long integer access is more efficient, the operating system allocates the buffer on an address whose size in bytes is a multiple of four.
The only way to release a buffer allocated with MAPIAllocateMore is to pass the buffer pointer specified in the lpObject parameter to the MAPIFreeBuffer function. The link between the memory buffers allocated with MAPIAllocateBuffer and MAPIAllocateMore enables MAPIFreeBuffer to release both buffers with a single call.