Whenever possible, try to retrieve or modify a property with the IMAPIProp::GetProps and IMAPIProp::SetProps methods. Unless the property you are working with is very large, these methods should be adequate. The other alternative is to read from or write to a stream with the OLE interface IStream. Streams can handle very large properties successfully, but they are a greater drain on resources because they require the OLE libraries. Use the IStream interface only after your call to IMAPIProp::GetProps or IMAPIProp::SetProps fails.