Sends a message via the resident mail host (if any) with the document as an attachment.
OnFileSendMail calls OnSaveDocument to serialize (save) untitled and modified documents to a temporary file, which is then sent via electronic mail. If the document has not been modified, a temporary file is not needed; the original is sent. OnFileSendMail loads MAPI32.DLL if it has not already been loaded.
Unlike the implementation of OnFileSendMail for CDocument, this function handles compound files correctly.