This content is no longer actively maintained. It is provided as is, for anyone who may still be using these technologies, with no warranties or claims of accuracy with regard to the most recent product version or service release. The Exchange OLE DB provider supports data types based on OLE DB DBTYPEs. However, because the Exchange store does not support unsigned integers, ExOLEDB converts the unsigned values to signed values. For example, properties of type VT_UI4 (unsigned long) are stored as the MAPI type PT_I4 (signed long). When the property is queried or enumerated, it is listed in its converted form as a signed long.
Similarly, ExOLEDB does not support conversions between vector types (for example, converting from DBVECTOR_I4 to DBVECTOR_I8, DB_UI8 to DB_I8, DBTIME or DBTIMESTAMP to DBFILETIME). Attempting to convert between vector types will return the HRESULT value E_CANTCONVERTVALUE.